Science.gov

Sample records for aggregation takes place

  1. Does olfactory specific satiety take place in a natural setting?

    PubMed

    Fernandez, P; Bensafi, M; Rouby, C; Giboreau, A

    2013-01-01

    Olfactory-specific satiety (OSS) is characterized by a specific decrease in the odor pleasantness of a food eaten to satiety or smelled without ingestion. The usual protocol for studying OSS takes place in laboratory, a setting rather removed from the real world. Here, we set out to examine OSS in a natural setting: during a meal in a restaurant. We hypothesized that an aroma contained in a food that is eaten at the beginning of a meal decreases the pleasantness of the flavor of a food with the same aroma eaten at the end of the meal. In the first experiment (Experiment 1), a test group received an appetizer flavored with a test aroma (anise) at the beginning of the meal. After the main dish, they received a dessert flavored with the same aroma. A control group received the same aromatized dessert, but after a non-aromatized appetizer. This experiment was replicated (Experiment 2) using verbena as the test aroma. For both experiments, results revealed that aroma pleasantness, but not intensity or familiarity, significantly decreased in the test groups vs. the control groups. These findings extend the concept of OSS to a realistic eating context. PMID:23079143

  2. 49 CFR 40.221 - Where does an alcohol test take place?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 1 2012-10-01 2012-10-01 false Where does an alcohol test take place? 40.221... WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Testing Sites, Forms, Equipment and Supplies Used in Alcohol Testing § 40.221 Where does an alcohol test take place? (a) A DOT alcohol test must take place at...

  3. 49 CFR 40.221 - Where does an alcohol test take place?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 1 2013-10-01 2013-10-01 false Where does an alcohol test take place? 40.221... WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Testing Sites, Forms, Equipment and Supplies Used in Alcohol Testing § 40.221 Where does an alcohol test take place? (a) A DOT alcohol test must take place at...

  4. 49 CFR 40.221 - Where does an alcohol test take place?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 1 2011-10-01 2011-10-01 false Where does an alcohol test take place? 40.221... WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Testing Sites, Forms, Equipment and Supplies Used in Alcohol Testing § 40.221 Where does an alcohol test take place? (a) A DOT alcohol test must take place at...

  5. Kiwifruit: taking its place in the global fruit bowl.

    PubMed

    Ward, Carol; Courtney, David

    2013-01-01

    While the world total production of kiwifruit has increased by over 50% during the last decade, the kiwifruit remains a niche fruit, taking up an estimated 0.22% of the global fruit bowl, which is dominated by apples, oranges, and bananas. Even though kiwifruit's share of the global fruit bowl has remained largely unchanged over the past 15 years, the scope for growth in the category is significant, with the nutritional and production characteristics of kiwifruit being on the right side of key global consumer trends around health and sustainability. Taking advantage of these consumer trends is one of two key challenges for the global kiwifruit industry. The second challenge is to harness the diverse natural and cultivated range of kiwifruit varieties (colors, flavors, sizes, and shapes) to stimulate the interest of consumers and grow the share of kiwifruit in the fruit basket through selecting cultivars that can develop meaningful market segments and meet consumer demand.

  6. Kiwifruit: taking its place in the global fruit bowl.

    PubMed

    Ward, Carol; Courtney, David

    2013-01-01

    While the world total production of kiwifruit has increased by over 50% during the last decade, the kiwifruit remains a niche fruit, taking up an estimated 0.22% of the global fruit bowl, which is dominated by apples, oranges, and bananas. Even though kiwifruit's share of the global fruit bowl has remained largely unchanged over the past 15 years, the scope for growth in the category is significant, with the nutritional and production characteristics of kiwifruit being on the right side of key global consumer trends around health and sustainability. Taking advantage of these consumer trends is one of two key challenges for the global kiwifruit industry. The second challenge is to harness the diverse natural and cultivated range of kiwifruit varieties (colors, flavors, sizes, and shapes) to stimulate the interest of consumers and grow the share of kiwifruit in the fruit basket through selecting cultivars that can develop meaningful market segments and meet consumer demand. PMID:23394979

  7. 2012 CCCC Chair's Address: Stories Take Place--A Performance in One Act

    ERIC Educational Resources Information Center

    Powell, Malea

    2012-01-01

    This is a written version of the address that Malea Powell gave at the Conference on College Composition and Communication (CCCC) Convention in St. Louis, Missouri, on Thursday, March 22, 2012. This address is a collection of stories. According to her, stories take place. Stories practice place into space. Stories produce habitable spaces. She…

  8. Studying Activities That Take Place in Speech Interactions: A Theoretical and Methodological Framework

    ERIC Educational Resources Information Center

    Saint-Dizier de Almeida, Valérie; Colletta, Jean-Marc; Auriac-Slusarczyk, Emmanuelle; Specogna, Antonietta; Simon, Jean-Pascal; Fiema, Gabriela; Luxembourger, Christophe

    2016-01-01

    The paper proposes a theoretical and methodological framework based on a pluralistic, concerted approach to the study of activities that take place in and through speech interactions. The framework has a general scope, applying to any collective activity taking form through language interactions. It contributes to a fuller understanding of the…

  9. Tau Phosphorylation, Aggregation, and Cell Toxicity

    PubMed Central

    Avila, J.; Santa-María, I.; Pérez, M.; Hernández, F.; Moreno, F.

    2006-01-01

    Protein aggregation takes place in many neurodegenerative disorders. However, there is a controversy about the possible toxicity of these protein aggregates. In this review, this controversy is discussed, focussing on the tau aggregation that takes place in those disorders known as tauopathies. PMID:17047313

  10. Questions and Answers Regarding Actions to Take When Ending Shelter-in-Place

    SciTech Connect

    Shumpert, B.

    2003-12-30

    Shelter-in-place has found increasing acceptance as an effective protective action option for communities participating in the Chemical Stockpile Emergency Preparedness Program. Studies have confirmed that it can provide optimum protection under certain accident conditions. However, emergency managers and planners, as well as the public, continue to be troubled by the need to end sheltering when the plume has passed in order to avoid sustained exposure to the small amount of agent that has penetrated the shelter. One of the concerns posed by this necessity is uncertainty regarding what hazards will then be faced in the environment outside the shelter and what actions can be taken to avoid those hazards. This report attempts to address those uncertainties. It recognizes that there is an extremely low probability that the environment outside the shelter will be contaminated with chemical agent residue. However, as people comply with an official recommendation to leave their shelters, they probably can't be certain that the environment is free from contamination. Therefore, this report identifies and explains specific and simple actions they can take to avoid the possibility of exposure to chemical agent hazards outside their shelters. It addresses such issues as the actions people should take upon ending shelter-in-place, what clothing they should wear, how they should handle animals, and what they should do about food in their homes and produce in their gardens.

  11. I'm so Aggregated...and I Think I Like It: Taking Another Look at Electronic Journal Aggregation

    ERIC Educational Resources Information Center

    Emery, Jill

    2008-01-01

    It has been a decade since the first aggregator journal packages began to become available at academic and public libraries throughout the United States of America. During these 10 years, the library and information science community has published numerous articles on the pros and cons of this method of delivery and these collections, more than…

  12. 23 CFR 636.402 - What types of information exchange may take place after the release of the RFP document?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false What types of information exchange may take place after... What types of information exchange may take place after the release of the RFP document? Certain types.... These communication methods are optional. Type of information exchange When Purpose Parties involved...

  13. 49 CFR 40.41 - Where does a urine collection for a DOT drug test take place?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 1 2012-10-01 2012-10-01 false Where does a urine collection for a DOT drug test... in DOT Urine Collections § 40.41 Where does a urine collection for a DOT drug test take place? (a) A urine collection for a DOT drug test must take place in a collection site meeting the requirements...

  14. 49 CFR 40.41 - Where does a urine collection for a DOT drug test take place?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 1 2013-10-01 2013-10-01 false Where does a urine collection for a DOT drug test... in DOT Urine Collections § 40.41 Where does a urine collection for a DOT drug test take place? (a) A urine collection for a DOT drug test must take place in a collection site meeting the requirements...

  15. 49 CFR 40.41 - Where does a urine collection for a DOT drug test take place?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 1 2014-10-01 2014-10-01 false Where does a urine collection for a DOT drug test... in DOT Urine Collections § 40.41 Where does a urine collection for a DOT drug test take place? (a) A urine collection for a DOT drug test must take place in a collection site meeting the requirements...

  16. 23 CFR 636.402 - What types of information exchange may take place after the release of the RFP document?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 23 Highways 1 2013-04-01 2013-04-01 false What types of information exchange may take place after... What types of information exchange may take place after the release of the RFP document? Certain types.... The following table summarizes the types of communications that will be discussed in this...

  17. 23 CFR 636.402 - What types of information exchange may take place after the release of the RFP document?

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 23 Highways 1 2011-04-01 2011-04-01 false What types of information exchange may take place after... What types of information exchange may take place after the release of the RFP document? Certain types.... The following table summarizes the types of communications that will be discussed in this...

  18. 23 CFR 636.402 - What types of information exchange may take place after the release of the RFP document?

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 23 Highways 1 2012-04-01 2012-04-01 false What types of information exchange may take place after... What types of information exchange may take place after the release of the RFP document? Certain types.... The following table summarizes the types of communications that will be discussed in this...

  19. [Marketing approval and market surveillance of medical devices in Germany: Where does policy integration take place?].

    PubMed

    Lang, Achim

    2014-01-01

    Since 2011 new regulatory measures regarding medical devices have been set up with the aim to eliminate obstacles to innovations and to find more coordinated ways to marketing authorisation and market surveillance. This essay investigates whether these new and existing coordination mechanisms build up to a Joined-up Government approach. The analysis shows that the regulatory process should be adjusted along several dimensions. First, many organisations lack awareness regarding their stakeholders and focus solely on their immediate organisational activities. Second, the regulatory process (marketing authorisation and market surveillance) is too fragmented for an effective communication to take place. Finally, the underlying strategy process is an ad-hoc approach lacking continuity and continued involvement of, in particular, the responsible federal ministries.

  20. [Marketing approval and market surveillance of medical devices in Germany: Where does policy integration take place?].

    PubMed

    Lang, Achim

    2014-01-01

    Since 2011 new regulatory measures regarding medical devices have been set up with the aim to eliminate obstacles to innovations and to find more coordinated ways to marketing authorisation and market surveillance. This essay investigates whether these new and existing coordination mechanisms build up to a Joined-up Government approach. The analysis shows that the regulatory process should be adjusted along several dimensions. First, many organisations lack awareness regarding their stakeholders and focus solely on their immediate organisational activities. Second, the regulatory process (marketing authorisation and market surveillance) is too fragmented for an effective communication to take place. Finally, the underlying strategy process is an ad-hoc approach lacking continuity and continued involvement of, in particular, the responsible federal ministries. PMID:25066351

  1. The 'taking place' of health and wellbeing: towards non-representational theory.

    PubMed

    Andrews, Gavin J; Chen, Sandra; Myers, Samantha

    2014-05-01

    For the last two decades health geography has focused on the dynamics between health and place. Although the social constructivist perspective of much research has provided many insights into the meanings of health and health care arguably, mirroring progress in the parent discipline of human geography, there could be a far more serious engagement with non-representational theory and the 'taking place' of health and health care. To showcase the importance and potential of this broadly, the idea of wellbeing is re-approached. The paper reflects on the ways wellbeing has been treated in research primarily as a meaningful and relatively prescribed state of life, to the neglect of process. Based on this critique, a qualitative study then illustrates the most immediate and everyday ways wellbeing might arise through 'affect'; the pre-personal mobile energies and intensities that result from physical encounters within assemblages of bodies and objects. Indeed, theoretically the findings support the proposition that, at one level, wellbeing might not be taken from environment but instead might emerge as the affective environment. They certainly raise awareness of how much in health might originate at the surface, prior to meaning, within life's infinite spatial doings, and thus they launch some final thoughts on the wider challenges and opportunities for non-representational health geographies.

  2. What it Takes to Successfully Implement Technology for Aging in Place: Focus Groups With Stakeholders

    PubMed Central

    Wouters, Eveline JM; Luijkx, Katrien G; Vrijhoef, Hubertus JM

    2016-01-01

    Background There is a growing interest in empowering older adults to age in place by deploying various types of technology (ie, eHealth, ambient assisted living technology, smart home technology, and gerontechnology). However, initiatives aimed at implementing these technologies are complicated by the fact that multiple stakeholder groups are involved. Goals and motives of stakeholders may not always be transparent or aligned, yet research on convergent and divergent positions of stakeholders is scarce. Objective To provide insight into the positions of stakeholder groups involved in the implementation of technology for aging in place by answering the following questions: What kind of technology do stakeholders see as relevant? What do stakeholders aim to achieve by implementing technology? What is needed to achieve successful implementations? Methods Mono-disciplinary focus groups were conducted with participants (n=29) representing five groups of stakeholders: older adults (6/29, 21%), care professionals (7/29, 24%), managers within home care or social work organizations (5/29, 17%), technology designers and suppliers (6/29, 21%), and policy makers (5/29, 17%). Transcripts were analyzed using thematic analysis. Results Stakeholders considered 26 different types of technologies to be relevant for enabling independent living. Only 6 out of 26 (23%) types of technology were mentioned by all stakeholder groups. Care professionals mentioned fewer different types of technology than other groups. All stakeholder groups felt that the implementation of technology for aging in place can be considered a success when (1) older adults’ needs and wishes are prioritized during development and deployment of the technology, (2) the technology is accepted by older adults, (3) the technology provides benefits to older adults, and (4) favorable prerequisites for the use of technology by older adults exist. While stakeholders seemed to have identical aims, several underlying

  3. Makro- and micromorphological evidence of processes taking place during Albeluvisol development in S Norway

    NASA Astrophysics Data System (ADS)

    Sauer, Daniela; Schülli-Maurer, Isabelle; Sperstad, Ragnhild; Sørensen, Rolf

    2014-05-01

    We studied two soil chronosequences in S Norway to identify processes involved in Albeluvisol formation. For this purpose, field observation of vertical and horizontal sections of soil profiles, soil chemical and mineralogical analyses were carried out, and in particular, micromorphological analysis was applied. The study area is located at the western and eastern side of the Oslofjord, S Norway, in the counties Vestfold and Østfold. This region is characterized by continuous glacio-isostatic uplift over the entire Holocene. Hence, the age of the land surface continuously increases from the coast towards higher elevations. Twelve soil profiles in loamy marine sediments were studied. Based on macro- and micromorphological observations and analytical data progressive soil formation is characterized as follows: As soon as the land surface is raised above sea level, five major processes are initiated: 1) development of deep desiccation cracks, forming a polygonal pattern; 2) compaction, taking place as soon as the coarse pores have been drained; 3) pyrite oxidation and release of sulfuric acid; 4) carbonate dissolution by acids from pyrite and iron oxidation resulting in rapid decarbonatization of the originally calcareous sediments; 5) precipitation of iron hypocoatings and coatings in the capillary fringe Soon after these very early processes have taken place, limited water permeability of the fine-textured sediments leads to horizon differentiation into Ah, Eg and Btg horizons within less than 2.1 ka. Eg horizons become lighter in colour with time. Also illuvial clay is already observed in the 2.1 ka-old soil. Soil pH in the upper part of the E horizon of this soil is already too low for significant clay mobilization. Clay illuviation is still active in all soils studied, but the upper boundary of the zone where pH favours clay mobilization is at 20-50 cm depth. Progressive clay illuviation over time is recorded in increasing thickness of clay coatings and

  4. OECD Global Science Forum's Astronomy Workshop to take place in Munich

    NASA Astrophysics Data System (ADS)

    2003-11-01

    members of the national astronomical community. The International Astronomical Union (IAU) and the European Southern Observatory (ESO) are explicitly represented. Experts from the world-wide astronomy community have been invited to set the stage and provide input for the discussions. The choice by Germany and the OECD to make Munich the venue of this Global Science Forum Workshop is no coincidence. It is a recognition of the important role played by many institutions in the Munich region in the field of Astronomy and Astrophysics. They include the Ludwig-Maximilians-Universität where the Workshop will take place, the Max-Planck-Institut für Astrophysik, the Max-Planck Institut für Extraterrestrische Physik and the European Southern Observatory. These institutions are all participating in large programmes and projects in astronomy. ESO, for its part, is at the leading edge of world astronomy with its flagship facility, the Very Large Telescope in Paranal (Chile) and the newly started ALMA project at Chajnantor (Chile), being carried out in partnership between Europe and North America. Public Talks (Munich) on December 1, 2003 As a prelude to the Workshop, two public keynote presentations will take place on December 1 at the Deutsches Museum in Munich at 18:00 CET. The speakers are Malcolm Longair, Jacksonian Professor of Natural Philosophy and Head of Laboratory, Cavendish Laboratory, Cambridge (UK) and Martin Harwit, Professor Emeritus of Astronomy, Cornell University, and former Director of the National Air and Space Museum, Washington, DC (USA). The talks will be given in English and the entry to this public event is free. Professor Longair will speak on "Astrophysics and Cosmology in the Twenty-First Century" and Professor Harwit will speak on "The Growth of Understanding of our Universe". You can find more informaton on the Public Talks web page.

  5. Aggregate measures of ecosystem services: can we take the pulse of nature?

    USGS Publications Warehouse

    Meyerson, L.A.; Baron, J.; Melillo, J.M.; Naiman, R.J.; O'Malley, R.I.; Orians, G.; Palmer, Margaret A.; Pfaff, Alexander S.P.; Running, S.W.; Sala, O.E.

    2005-01-01

    National scale aggregate indicators of ecosystem services are useful for stimulating and supporting a broad public discussion about trends in the provision of these services. There are important considerations involved in producing an aggregate indicator, including whether the scientific and technological capacity exists, how to address varying perceptions of the societal importance of different services, and how to communicate information about these services to both decision makers and the general public. Although the challenges are formidable, they are not insurmountable. Quantification of ecosystem services and dissemination of information to decision makers and the public is critical for the responsible and sustainable management of natural resources.

  6. "Why Are We Here?" Taking "Place" into Account in UK Outdoor Environmental Education

    ERIC Educational Resources Information Center

    Harrison, Sam

    2010-01-01

    "Place" is an under-researched and poorly documented element of UK outdoor environmental education. In the international literature, North American and Australian researchers and practitioners show considerable attention to "place". Yet UK outdoor environmental educators and researchers seem to have neglected this area despite calls for increased…

  7. 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.

  8. An Experimental Investigation of the Process of Isotope Exchange that Takes Place when Heavy Water Is Exposed to the Atmosphere

    ERIC Educational Resources Information Center

    Deeney, F. A.; O'Leary, J. P.

    2009-01-01

    We have used the recently developed method for rapid measurement of maximum density temperature to determine the rate at which hydrogen and deuterium isotope exchange takes place when a sample of heavy water is exposed to the atmosphere. We also provide a simple explanation for the observed linear rate of transition. (Contains 2 figures.)

  9. 23 CFR 636.402 - What types of information exchange may take place after the release of the RFP document?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 23 Highways 1 2014-04-01 2014-04-01 false What types of information exchange may take place after the release of the RFP document? 636.402 Section 636.402 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS DESIGN-BUILD CONTRACTING Exchanges § 636.402 What types of information exchange may...

  10. Taking the High Ground: Geothermal's Place in the Revolving Energy Market

    SciTech Connect

    Jaros, Richard

    1992-03-24

    It's a genuine privilege for me to be here today. As Dr. Mock mentioned, I have been President of California Energy for not yet three months and have a total tenure in the industry of only one year. As a newcomer to the industry, I am honored to address this group and share my views on ''The Opportunities and Challenges for Expanding Geothermal Energy''. You will see that my outlook for our industry is generally optimistic, shaped in part, perhaps by a newcomer's enthusiasm, but largely I think by my analysis of the opportunities which are open to us as an industry. Many of you and your predecessors over the last 20 years pioneered the geothermal industry in the United States. The risks were great, the results sometimes rewarding, sometimes disappointing. Government and the private sector forged an alliance that moved the industry ahead. Developers, utilities and federal land managers worked together to bring projects on line. Government helped identify geothermal areas, in many cases doing exploration work. The geothermal pioneers had to form entirely new, multi-disciplinary teams to solve problems unique to this resource. From discovery of fields, to environmental mitigation, to management of reservoirs and all of the steps in between, new teams had to be assembled. Geologists, geochemists, hydrologists, reservoir engineers and drilling technologists now apply their skills. Even anthropologists and biologists routinely get into the act in the environmental assessment phase of development. The care that our industry is taking today to do the job right reflects a maturing industry with high standards of performance. To be sure, mistakes were made in the early years, but the industry learned from them. We all know the value of responsible development and resource management to the long-term future of our industry. Improvements in technology and more efficient operations have helped lower our costs and improve our competitiveness. Our industry's progress has also

  11. 23 CFR 636.401 - What types of information exchange may take place prior to the release of the RFP document?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 23 Highways 1 2010-04-01 2010-04-01 false What types of information exchange may take place prior... What types of information exchange may take place prior to the release of the RFP document? Verbal or written information exchanges (such as in the first-phase of a two-phase selection procedure) must...

  12. LIDAR for remote sensing of contaminations on water and earth surfaces taking place during oil-gas production

    NASA Astrophysics Data System (ADS)

    Pashayev, A.; Tagiyev, B.; Allahverdiyev, K.; Musayev, A.; Sadikhov, I.

    2015-12-01

    Remote sensing of contaminations on water and earth surfaces (oil spills, films) taking place during oil-gas extraction is an interesting and actual problem. This problem may be solved by using different methods of optical spectroscopy, including: •Raman scattering; •light induced breakdown spectroscopy (LIBS); •fluorescence spectroscopy. Fluorescence Light Detection and Ranging (LIDAR) LIDARs are successfully used for remote sensing of chemical and biological substances at atmosphere. A new laser induced fluorescence (LIF) KA-14 LIDAR system for detecting of oil spills on the sea surface was employed at the National Aviation Academy of Azerbaijan. LIDAR's parameters are as follows: •laser CFR 200- type QUANTEL, λ = 355 nm, beam Ø = 5.35 mm, f = 20 Hz, pulse duration τ = 7 ns, pulse power 60 mJ; •diameter of Newtonian- type telescope is 200 mm; •collimator expansion of the laser beam diameter- not less than 3; •angle range of telescope measurements relative to horizon: from -20 to +20 degree; •spectral range of measurements: from 380 to 750 nm, number of spectral channels- 32; •maximum range of measurements- not less than 250 m. This LIDAR is the first performing these kind of research not only on the Azerbaijan beach of Caspian sea, but also on the earth places of Absheron peninsula, where oil-gas production takes place. We hope that the performance of LIDAR will have an International recognition and will make noticeable input on the International Research of Caspian sea surfaces.

  13. Taking Advantage of Electric Field Induced Bacterial Aggregation for the Study of Interactions between Bacteria and Macromolecules by Capillary Electrophoresis.

    PubMed

    Sisavath, Nicolas; Got, Patrice; Charrière, Guillaume M; Destoumieux-Garzon, Delphine; Cottet, Hervé

    2015-07-01

    The quantification of interaction stoichiometry and binding constant between bacteria (or other microorganism) and (macro)molecules remains a challenging issue for which only a few adapted methods are available. In this paper, a new methodology was developed for the determination of the interaction stoichiometry and binding constant between bacteria and (macro)molecules. The originality of this work is to take advantage of the bacterial aggregation phenomenon to directly quantify the free ligand concentration in equilibrated bacteria-ligand mixtures using frontal analysis continuous capillary electrophoresis. The described methodology does not require any sample preparation such as filtration step or centrifugation. It was applied to the study of interactions between Erwinia carotovora and different generations of dendrigraft poly-L-lysines leading to quantitative information (i.e., stoichiometry and binding site constant). High stoichiometries in the order of 10(6)-10(7) were determined between nanometric dendrimer-like ligands and the rod-shaped micrometric bacteria. The effect of the dendrimer generation on the binding constant and the stoichiometry is discussed. Stoichiometries were compared with those obtained by replacing the bacteria by polystyrene microbeads to demonstrate the internalization of the ligands inside the bacteria and the increase of the specific surface via the formation of vesicles. PMID:26086209

  14. Structural and functional changes in the olfactory pathway of adult Drosophila take place at a critical age.

    PubMed

    Devaud, Jean-Marc; Acebes, Angel; Ramaswami, Mani; Ferrús, Alberto

    2003-07-01

    The olfactory system of several holometabolous insect species undergoes anatomical changes after eclosion of the imago, following those occurring during metamorphosis. In parallel, odor experience and learning performance also evolve with age. Here, we analyze the case of adult Drosophila females. Synaptogenesis in the antennal lobe (AL) starts in late pupa and continues during the first days of adult life, at the same time as the behavioral response to odors matures. Individual olfactory glomeruli (DM6, DM2, and V) display specific growth patterns between days 1 and 12 of adult life. Experience can modify the olfactory pathway both structurally and functionally as shown by adaptation experiments. The modifications associated with this form of nonassociative learning seem to take place at a critical age. Exposure to benzaldehyde at days 2-5 of adult life, but not at 8-11, causes behavioral adaptation as well as structural changes in DM2 and V glomeruli. Altered levels in intracellular cAMP, caused by dunce and rutabaga mutants, do not affect the normal changes in glomerular size, at least at day 6 of development, but they prevent those elicited by experience, establishing a molecular difference between glomerular changes of intrinsic versus environmental origin. Taken together, these data demonstrate an imprinting-like phenomenon in the olfactory pathway of young Drosophila adults, and illustrate its glomerulus-specific dynamics.

  15. Placing Local Aggregations in a Larger-Scale Context: Hierarchical Modeling of Black-Footed Albatross Dispersion

    PubMed Central

    Jahncke, J.; Hyrenbach, K. D.

    2016-01-01

    At-sea surveys facilitate the study of the distribution and abundance of marine birds along standardized transects, in relation to changes in the local environmental conditions and large-scale oceanographic forcing. We analyzed the form and the intensity of black-footed albatross (Phoebastria nigripes: BFAL) spatial dispersion off central California, using five years (2004–2008) of vessel-based surveys of seven replicated survey lines. We related BFAL patchiness to local, regional and basin-wide oceanographic variability using two complementary approaches: a hypothesis-based model and an exploratory analysis. The former tested the strength and sign of hypothesized BFAL responses to environmental variability, within a hierarchical atmosphere—ocean context. The latter explored BFAL cross-correlations with atmospheric / oceanographic variables. While albatross dispersion was not significantly explained by the hierarchical model, the exploratory analysis revealed that aggregations were influenced by static (latitude, depth) and dynamic (wind speed, upwelling) environmental variables. Moreover, the largest BFAL patches occurred along the survey lines with the highest densities, and in association with shallow banks. In turn, the highest BFAL densities occurred during periods of negative Pacific Decadal Oscillation index values and low atmospheric pressure. The exploratory analyses suggest that BFAL dispersion is influenced by basin-wide, regional-scale and local environmental variability. Furthermore, the hypothesis-based model highlights that BFAL do not respond to oceanographic variability in a hierarchical fashion. Instead, their distributions shift more strongly in response to large-scale ocean—atmosphere forcing. Thus, interpreting local changes in BFAL abundance and dispersion requires considering diverse environmental forcing operating at multiple scales. PMID:27124491

  16. Placing Local Aggregations in a Larger-Scale Context: Hierarchical Modeling of Black-Footed Albatross Dispersion.

    PubMed

    Michael, P E; Jahncke, J; Hyrenbach, K D

    2016-01-01

    At-sea surveys facilitate the study of the distribution and abundance of marine birds along standardized transects, in relation to changes in the local environmental conditions and large-scale oceanographic forcing. We analyzed the form and the intensity of black-footed albatross (Phoebastria nigripes: BFAL) spatial dispersion off central California, using five years (2004-2008) of vessel-based surveys of seven replicated survey lines. We related BFAL patchiness to local, regional and basin-wide oceanographic variability using two complementary approaches: a hypothesis-based model and an exploratory analysis. The former tested the strength and sign of hypothesized BFAL responses to environmental variability, within a hierarchical atmosphere-ocean context. The latter explored BFAL cross-correlations with atmospheric / oceanographic variables. While albatross dispersion was not significantly explained by the hierarchical model, the exploratory analysis revealed that aggregations were influenced by static (latitude, depth) and dynamic (wind speed, upwelling) environmental variables. Moreover, the largest BFAL patches occurred along the survey lines with the highest densities, and in association with shallow banks. In turn, the highest BFAL densities occurred during periods of negative Pacific Decadal Oscillation index values and low atmospheric pressure. The exploratory analyses suggest that BFAL dispersion is influenced by basin-wide, regional-scale and local environmental variability. Furthermore, the hypothesis-based model highlights that BFAL do not respond to oceanographic variability in a hierarchical fashion. Instead, their distributions shift more strongly in response to large-scale ocean-atmosphere forcing. Thus, interpreting local changes in BFAL abundance and dispersion requires considering diverse environmental forcing operating at multiple scales. PMID:27124491

  17. The non-protein amino acid BMAA is misincorporated into human proteins in place of L-serine causing protein misfolding and aggregation.

    PubMed

    Dunlop, Rachael Anne; Cox, Paul Alan; Banack, Sandra Anne; Rodgers, Kenneth John

    2013-01-01

    Mechanisms of protein misfolding are of increasing interest in the aetiology of neurodegenerative diseases characterized by protein aggregation and tangles including Amyotrophic Lateral Sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), Lewy Body Dementia (LBD), and Progressive Supranuclear Palsy (PSP). Some forms of neurodegenerative illness are associated with mutations in genes which control assembly of disease related proteins. For example, the mouse sticky mutation sti, which results in undetected mischarging of tRNA(Ala) with serine resulting in the substitution of serine for alanine in proteins causes cerebellar Purkinje cell loss and ataxia in laboratory animals. Replacement of serine 422 with glutamic acid in tau increases the propensity of tau aggregation associated with neurodegeneration. However, the possibility that environmental factors can trigger abnormal folding in proteins remains relatively unexplored. We here report that a non-protein amino acid, β-N-methylamino-L-alanine (BMAA), can be misincorporated in place of L-serine into human proteins. We also report that this misincorporation can be inhibited by L-serine. Misincorporation of BMAA into human neuroproteins may shed light on putative associations between human exposure to BMAA produced by cyanobacteria and an increased incidence of ALS. PMID:24086518

  18. Young People Take Their Rightful Places as Full and Contributing Members of a World Class Workforce: Philadelphia Youth Network Annual Report 2006

    ERIC Educational Resources Information Center

    Philadelphia Youth Network, 2006

    2006-01-01

    The title of this year's annual report has particular meaning for all of the staff at the Philadelphia Youth Network. The phrase derives from Philadelphia Youth Network's (PYN's) new vision statement, developed as part of its recent strategic planning process, which reads: All of our city's young people take their rightful places as full and…

  19. Placing the power of real options analysis into the hands of natural resource managers - taking the next step.

    PubMed

    Nelson, Rohan; Howden, Mark; Hayman, Peter

    2013-07-30

    This paper explores heuristic methods with potential to place the analytical power of real options analysis into the hands of natural resource managers. The complexity of real options analysis has led to patchy or ephemeral adoption even by corporate managers familiar with the financial-market origins of valuation methods. Intuitively accessible methods for estimating the value of real options have begun to evolve, but their evaluation has mostly been limited to researcher-driven applications. In this paper we work closely with Bush Heritage Australia to evaluate the potential of real options analysis to support the intuitive judgement of conservation estate managers in covenanting land with uncertain future conservation value due to climate change. The results show that modified decision trees have potential to estimate the option value of covenanting individual properties while time and ongoing research resolves their future conservation value. Complementing this, Luehrman's option space has potential to assist managers with limited budgets to increase the portfolio value of multiple properties with different conservation attributes.

  20. Placing the power of real options analysis into the hands of natural resource managers - taking the next step.

    PubMed

    Nelson, Rohan; Howden, Mark; Hayman, Peter

    2013-07-30

    This paper explores heuristic methods with potential to place the analytical power of real options analysis into the hands of natural resource managers. The complexity of real options analysis has led to patchy or ephemeral adoption even by corporate managers familiar with the financial-market origins of valuation methods. Intuitively accessible methods for estimating the value of real options have begun to evolve, but their evaluation has mostly been limited to researcher-driven applications. In this paper we work closely with Bush Heritage Australia to evaluate the potential of real options analysis to support the intuitive judgement of conservation estate managers in covenanting land with uncertain future conservation value due to climate change. The results show that modified decision trees have potential to estimate the option value of covenanting individual properties while time and ongoing research resolves their future conservation value. Complementing this, Luehrman's option space has potential to assist managers with limited budgets to increase the portfolio value of multiple properties with different conservation attributes. PMID:23702285

  1. Evaluation of the bond strength of root-end placed mineral trioxide aggregate and Biodentine in the absence/presence of blood contamination

    PubMed Central

    Akcay, Huseyin; Arslan, Hakan; Akcay, Merve; Mese, Merve; Sahin, Naciye Nur

    2016-01-01

    Objective: Mineral trioxide aggregate (MTA) has been accepted as an appropriate root-end filling material in endodontic microsurgery because of setting ability in the wet environment. The aim of this study was to assess the bond strength of root-end placed MTA and Biodentine (Septodont, Saint Maur des Fossés, France) in the absence/presence of blood contamination. Materials and Methods: Forty-eight single-rooted maxillary incisors were used. subsequent to root-end resection and apical preparation using ultrasonic retro-tips, the specimens were randomly separated into two groups according to the root-end filling materials: MTA (Cerkamed Medical Company, Stalowa, Poland) or Biodentine. The specimens were then separated into two subgroups according to storage condition (absence/presence of blood) (n = 12). After obtaining 2.0 ± 0.1 mm slices, push-out tests were performed. Each slice was examined under a stereomicroscope to evaluate the failure mode. The data were analyzed using two-way analysis of variance and Tukey's post hoc test for multiple comparisons. The failure modes were analyzed using the Chi-square test (P = 0.05). Results: The bond strength was significantly affected by the presence of blood contamination and root-end filling material type (P < 0.001). Biodentine had better bond strength than MTA (P < 0.001). The most common failure type was adhesive failure. According to the Chi-square test, there were no statistically significant differences among the groups (P = 0.394). Conclusions: Biodentine had better bond strength values compared to MTA, and the bond strength of both MTA and Biodentine as root-end filling materials was negatively affected by the presence of blood. PMID:27403056

  2. Assembly of the ligand-binding conformation of Mr 46,000 mannose 6- phosphate-specific receptor takes place before reaching the Golgi complex

    PubMed Central

    1990-01-01

    The early steps in the biosynthesis of Mr 46,000 mannose 6-phosphate- specific receptor (MPR 46) have been studied by in vivo labeling of transfected BHK cells. The acquisition of phosphomannan-binding activity was compared with changes in protein structure and posttranslational modifications of MPR 46. Intramolecular disulfide bonds were formed before MPR 46 acquired a ligand-binding conformation. A conformational change that resulted in increased trypsin resistance, formation of highly immunogenic epitopes and assembly to noncovalently linked homodimers was observed almost simultaneously with the acquisition of ligand-binding activity. MPR 46 was shown to acquire ligand-binding activity before N-linked oligosaccharides were processed to complex-type forms. Maturation of the ligand-binding conformation was observed under conditions where transport to the Golgi was blocked by lowering the temperature to 16 degrees C, or by addition of brefeldin A or dinitrophenol to the medium at 37 degrees C. This suggests that receptor maturation and assembly take place before reaching the Golgi complex. The affinity towards phosphomannan- containing ligands was shown to be similar for the high-mannose and complex-glycosylated forms of MPR 46. PMID:2157722

  3. Places for Children - Children's Places

    ERIC Educational Resources Information Center

    Rasmussen, Kim

    2004-01-01

    In their everyday lives, children largely stay within and relate to three settings - their homes, schools and recreational institutions. These environments have been created by adults and designated by them as "places for children". A more differentiated picture of children's spatial culture emerges when children discuss and take photographs of…

  4. Place and Being

    ERIC Educational Resources Information Center

    Cannatella, Howard

    2007-01-01

    Do places matter educationally? When Edward Casey remarks: "The world is, minimally and forever, a place-world", we might take this statement as presupposing without argument that places exist as a given, that we know what a place is, a point that Aristotle would have never taken for granted and in fact neither does Casey. I find Casey's remark…

  5. Place-focused physical activity research, human agency, and social justice in public health: taking agency seriously in studies of the built environment.

    PubMed

    Blacksher, Erika; Lovasi, Gina S

    2012-03-01

    Built environment characteristics have been linked to health outcomes and health disparities. However, the effects of an environment on behavior may depend on human perception, interpretation, motivation, and other forms of human agency. We draw on epidemiological and ethical concepts to articulate a critique of research on the built environment and physical activity. We identify problematic assumptions and enumerate both scientific and ethical reasons to incorporate subjective perspectives and public engagement strategies into built environment research and interventions. We maintain that taking agency seriously is essential to the pursuit of health equity and the broader demands of social justice in public health, an important consideration as studies of the built environment and physical activity increasingly focus on socially disadvantaged communities. Attention to how people understand their environment and navigate competing demands can improve the scientific value of ongoing efforts to promote active living and health, while also better fulfilling our ethical obligations to the individuals and communities whose health we strive to protect.

  6. Effects of proton irradiation on a gas phase in which condensation takes place. I Negative Mg-26 anomalies and Al-26. [applied to solar and meteoritic composition

    NASA Technical Reports Server (NTRS)

    Heymann, D.; Dziczkaniec, M.; Walker, A.; Huss, G.; Morgan, J. A.

    1978-01-01

    In the present paper, isotopic effects in magnesium generated in a proton-irradiated gas phase are examined, taking only (p,n), (p,d), and (p, alpha) reactions in magnesium, aluminum, and silicon into consideration. In the presence of proton radiation, the three elements are 'removed' from the gas phase by condensation. It is required that a value of Al-26/Al-27 greater than 6 times 10 to the -5th must be reached, consistent with the value deduced by Lee Papanastassiou, and Wasserburg (1976) from their studies of the Allende meteorite. The calculations show that fast aluminum condensation reduces the required proton fluence substantially, that a significant fraction of aluminum remains uncondensed when the above value of the Al-26/Al-27 ratio is reached, that a detectable MG-24 excess is very likely to occur, that detectable negative MG-28 anomalies can be generated, and that proton fluxes and irradiation times can be varied simultaneously, and over a wide range of values, without significant changes in the required proton fluence.

  7. Leaf processing behaviour in Atta leafcutter ants: 90% of leaf cutting takes place inside the nest, and ants select pieces that require less cutting.

    PubMed

    Garrett, Ryan W; Carlson, Katherine A; Goggans, Matthew Scott; Nesson, Michael H; Shepard, Christopher A; Schofield, Robert M S

    2016-01-01

    Leafcutter ants cut trimmings from plants, carry them to their underground nests and cut them into smaller pieces before inoculating them with a fungus that serves as a primary food source for the colony. Cutting is energetically costly, so the amount of cutting is important in understanding foraging energetics. Estimates of the cutting density, metres of cutting per square metre of leaf, were made from samples of transported leaf cuttings and of fungal substrate from field colonies of Atta cephalotes and Atta colombica. To investigate cutting inside the nest, we made leaf-processing observations of our laboratory colony, A. cephalotes. We did not observe the commonly reported reduction of the leaf fragments into a pulp, which would greatly increase the energy cost of processing. Video clips of processing behaviours, including behaviours that have not previously been described, are linked. An estimated 2.9 (±0.3) km of cutting with mandibles was required to reduce a square metre of leaf to fungal substrate. Only about 12% (±1%) of this cutting took place outside of the nest. The cutting density and energy cost is lower for leaf material with higher ratios of perimeter to area, so we tested for, and found that the laboratory ants had a preference for leaves that were pre-cut into smaller pieces. Estimates suggest that the energy required to transport and cut up the leaf material is comparable to the metabolic energy available from the fungus grown on the leaves, and so conservation of energy is likely to be a particularly strong selective pressure for leafcutter ants. PMID:26909161

  8. Leaf processing behaviour in Atta leafcutter ants: 90% of leaf cutting takes place inside the nest, and ants select pieces that require less cutting

    PubMed Central

    Garrett, Ryan W.; Carlson, Katherine A.; Goggans, Matthew Scott; Nesson, Michael H.; Shepard, Christopher A.; Schofield, Robert M. S.

    2016-01-01

    Leafcutter ants cut trimmings from plants, carry them to their underground nests and cut them into smaller pieces before inoculating them with a fungus that serves as a primary food source for the colony. Cutting is energetically costly, so the amount of cutting is important in understanding foraging energetics. Estimates of the cutting density, metres of cutting per square metre of leaf, were made from samples of transported leaf cuttings and of fungal substrate from field colonies of Atta cephalotes and Atta colombica. To investigate cutting inside the nest, we made leaf-processing observations of our laboratory colony, A. cephalotes. We did not observe the commonly reported reduction of the leaf fragments into a pulp, which would greatly increase the energy cost of processing. Video clips of processing behaviours, including behaviours that have not previously been described, are linked. An estimated 2.9 (±0.3) km of cutting with mandibles was required to reduce a square metre of leaf to fungal substrate. Only about 12% (±1%) of this cutting took place outside of the nest. The cutting density and energy cost is lower for leaf material with higher ratios of perimeter to area, so we tested for, and found that the laboratory ants had a preference for leaves that were pre-cut into smaller pieces. Estimates suggest that the energy required to transport and cut up the leaf material is comparable to the metabolic energy available from the fungus grown on the leaves, and so conservation of energy is likely to be a particularly strong selective pressure for leafcutter ants. PMID:26909161

  9. Uncertainty calculation in the RIO air quality interpolation model and aggregation to yearly average and exceedance probability taking into account the temporal auto-correlation.

    NASA Astrophysics Data System (ADS)

    Maiheu, Bino; Nele, Veldeman; Janssen, Stijn; Fierens, Frans; Trimpeneers, Elke

    2010-05-01

    RIO is an operational air quality interpolation model developed by VITO and IRCEL-CELINE and produces hourly maps for different pollutant concentrations such as O3, PM10 and NO2 measured in Belgium [1]. The RIO methodology consists of residual interpolation by Ordinary Kriging of the residuals of the measured concentrations and pre-determined trend functions which express the relation between land cover information derived from the CORINE dataset and measured time-averaged concentrations [2]. RIO is an important tool for the Flemish administration and is among others used to report, as is required by each member state, on the air quality status in Flanders to the European Union. We feel that a good estimate of the uncertainty of the yearly average concentration maps and the probability of norm-exceedance are both as important as the values themselves. In this contribution we will discuss the uncertainties specific to the RIO methodology, where we have both contributions from the Ordinary Kriging technique as well as the trend functions. Especially the parameterisation of the uncertainty w.r.t. the trend functions will be the key indicator for the degree of confidence the model puts into using land cover information for spatial interpolation of pollutant concentrations. Next, we will propose a method which enables us to calculate the uncertainty on the yearly average concentrations as well as the number of exceedance days, taking into account the temporal auto-correlation of the concentration fields. It is clear that the autocorrelation will have a strong impact on the uncertainty estimation [3] of yearly averages. The method we propose is based on a Monte Carlo technique that generates an ensemble of interpolation maps with the correct temporal auto-correlation structure. From a generated ensemble, the calculation of norm-exceedance probability at each interpolation location becomes quite straightforward. A comparison with the ad-hoc method proposed in [3], where

  10. 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.

  11. COSMIC DUST AGGREGATION WITH STOCHASTIC CHARGING

    SciTech Connect

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

    2013-10-20

    The coagulation of cosmic dust grains is a fundamental process which takes place in astrophysical environments, such as presolar nebulae and circumstellar and protoplanetary disks. Cosmic dust grains can become charged through interaction with their plasma environment or other processes, and the resultant electrostatic force between dust grains can strongly affect their coagulation rate. Since ions and electrons are collected on the surface of the dust grain at random time intervals, the electrical charge of a dust grain experiences stochastic fluctuations. In this study, a set of stochastic differential equations is developed to model these fluctuations over the surface of an irregularly shaped aggregate. Then, employing the data produced, the influence of the charge fluctuations on the coagulation process and the physical characteristics of the aggregates formed is examined. It is shown that dust with small charges (due to the small size of the dust grains or a tenuous plasma environment) is affected most strongly.

  12. Prey aggregation is an effective olfactory predator avoidance strategy

    PubMed Central

    Dunn, Alison M.; Morrell, Lesley J.

    2014-01-01

    Predator–prey interactions have a major effect on species abundance and diversity, and aggregation is a well-known anti-predator behaviour. For immobile prey, the effectiveness of aggregation depends on two conditions: (a) the inability of the predator to consume all prey in a group and (b) detection of a single large group not being proportionally easier than that of several small groups. How prey aggregation influences predation rates when visual cues are restricted, such as in turbid water, has not been thoroughly investigated. We carried out foraging (predation) experiments using a fish predator and (dead) chironomid larvae as prey in both laboratory and field settings. In the laboratory, a reduction in visual cue availability (in turbid water) led to a delay in the location of aggregated prey compared to when visual cues were available. Aggregated prey suffered high mortality once discovered, leading to better survival of dispersed prey in the longer term. We attribute this to the inability of the dead prey to take evasive action. In the field (where prey were placed in feeding stations that allowed transmission of olfactory but not visual cues), aggregated (large groups) and semi-dispersed prey survived for longer than dispersed prey—including long term survival. Together, our results indicate that similar to systems where predators hunt using vision, aggregation is an effective anti-predator behaviour for prey avoiding olfactory predators. PMID:24918032

  13. Prey aggregation is an effective olfactory predator avoidance strategy.

    PubMed

    Johannesen, Asa; Dunn, Alison M; Morrell, Lesley J

    2014-01-01

    Predator-prey interactions have a major effect on species abundance and diversity, and aggregation is a well-known anti-predator behaviour. For immobile prey, the effectiveness of aggregation depends on two conditions: (a) the inability of the predator to consume all prey in a group and (b) detection of a single large group not being proportionally easier than that of several small groups. How prey aggregation influences predation rates when visual cues are restricted, such as in turbid water, has not been thoroughly investigated. We carried out foraging (predation) experiments using a fish predator and (dead) chironomid larvae as prey in both laboratory and field settings. In the laboratory, a reduction in visual cue availability (in turbid water) led to a delay in the location of aggregated prey compared to when visual cues were available. Aggregated prey suffered high mortality once discovered, leading to better survival of dispersed prey in the longer term. We attribute this to the inability of the dead prey to take evasive action. In the field (where prey were placed in feeding stations that allowed transmission of olfactory but not visual cues), aggregated (large groups) and semi-dispersed prey survived for longer than dispersed prey-including long term survival. Together, our results indicate that similar to systems where predators hunt using vision, aggregation is an effective anti-predator behaviour for prey avoiding olfactory predators.

  14. 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%.

  15. 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.

  16. A mechanistic model of tau amyloid aggregation based on direct observation of oligomers

    NASA Astrophysics Data System (ADS)

    Shammas, Sarah L.; Garcia, Gonzalo A.; Kumar, Satish; Kjaergaard, Magnus; Horrocks, Mathew H.; Shivji, Nadia; Mandelkow, Eva; Knowles, Tuomas P. J.; Mandelkow, Eckhard; Klenerman, David

    2015-04-01

    Protein aggregation plays a key role in neurodegenerative disease, giving rise to small oligomers that may become cytotoxic to cells. The fundamental microscopic reactions taking place during aggregation, and their rate constants, have been difficult to determine due to lack of suitable methods to identify and follow the low concentration of oligomers over time. Here we use single-molecule fluorescence to study the aggregation of the repeat domain of tau (K18), and two mutant forms linked with familial frontotemporal dementia, the deletion mutant ΔK280 and the point mutant P301L. Our kinetic analysis reveals that aggregation proceeds via monomeric assembly into small oligomers, and a subsequent slow structural conversion step before fibril formation. Using this approach, we have been able to quantitatively determine how these mutations alter the aggregation energy landscape.

  17. 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.

  18. Adsorption-induced colloidal aggregation

    NASA Astrophysics Data System (ADS)

    Law, B. M.; Petit, J.-M.; Beysens, D.

    1998-03-01

    Reversible colloidal aggregation in binary liquid mixtures has been studied for a number of years. As the phase separation temperature of the liquid mixture is approached the thickness of an adsorption layer around the colloidal particles increases. Beysens and coworkers have demonstrated experimentally that this adsorption layer is intimately connected with the aggregation of the colloidal particles, however, no definitive theory has been available which can explain all of the experimental observations. In this contribution we describe an extension of the Derjaguin, Landau, Verwey, and Overbeek theory of colloidal aggregation which takes into account the presence of the adsorption layer and which more realistically models the attractive dispersion interactions. This modified theory can quantitatively account for many of the observed experimental features such as the characteristics of the aggregated state, the general shape of the aggregation line, and the temperature dependence of the second virial coefficient for a lutidine-water mixture containing a small volume fraction of silica colloidal particles.

  19. 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.

  20. 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.

  1. 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.

  2. Places to Go: Moodle

    ERIC Educational Resources Information Center

    Downes, Stephen

    2006-01-01

    Educators are becoming increasingly interested in alternatives to learning management systems (LMS) Blackboard and WebCT. Stephen Downes's column Places to Go turns to one internationally popular open source LMS--Moodle. Downes takes the reader through Moodle's Web site, which is simultaneously a Web site about its LMS and an example of what its…

  3. 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).

  4. Pathological Propagation through Cell-to-Cell Transmission of Non-Prion Protein Aggregates in Neurodegenerative Disorders

    PubMed Central

    Lee, Seung-Jae; Desplats, Paula; Sigurdson, Christina; Tsigelny, Igor; Masliah, Eliezer

    2016-01-01

    Neurodegenerative disorders such as Alzheimer's Disease, Parkinson's Disease, fronto-temporal dementia, Huntington's Disease and Creutzfeldt-Jakob Disease (CJD) are characterized by progressive accumulation of protein aggregates in selected brain regions. Protein misfolding and templated assembly into aggregates might result from an imbalance between protein synthesis, aggregation and clearance. While protein misfolding and aggregation occur in most neurodegenerative disorders, the concept of spreading and infectivity of aggregates in the CNS has been reserved to prion diseases such as CJD and bovine spongiform encephalopathy. Emerging evidence suggests that prion-like spreading may occur in other neurodegenerative disorders, taking place with secreted proteins, such as amyloid-β,) and cytosolic proteins, such as tau, huntingtin and α-synuclein. Underlying molecular mechanisms and therapeutic implications are discussed. PMID:21045796

  5. Induced growth of dendrite gold nanostructure by controlling self-assembly aggregation dynamics.

    PubMed

    Abdellatif, M H; Abdelrasoul, G N; Scarpellini, A; Marras, S; Diaspro, A

    2015-11-15

    Self-assembly of gold nanoparticles (AuNPs) is an important growth mode for fabricating functional materials. In this work we report a dendrite structure formed by slowing down the aggregation dynamics of AuNPs self-assembly. The obtained results show that the aggregation dynamics is dominated by the Reaction Limited Aggregation Model (RLA) more than the Diffusion Limited Aggregation Model (DLA). In which the repulsion due to electrostatic forces is dominant by the Van Der Walls attraction forces, and low sticking probability of nanoparticles. The aggregation dynamics of AuNPs can be slowed down if the water evaporation of the drop casted colloidal AuNPs on a quartz substrate is slowed. Slowing down the evaporation allows electrostatic repulsion forces to decrease gradually. At certain point, the attraction forces become higher than the electrostatic repulsion and hence cluster aggregation take place slowly. The slow aggregation dynamics allows the nanoparticles to sample all possible orientation in the sticking site, searching for the lowest energy configuration. The size distribution of the nanoparticles in liquid is confirmed using dynamic light scattering based on Stokes-Einstein equation for diffusion coefficient in water. X-ray and photoluminescence (PL) spectra of the sample after aggregation showed a shift which is related to the aggregation compared with non-aggregated colloidal nanoparticles in the solution. The study shows that dendrite self similar structure can be formed by slowing down the aggregation dynamics of nanoparticles as a result of minimizing the Helmholtz free surface energy of the system. PMID:26233557

  6. 1. GENERAL VIEW OF ENGINE PILE OF AGGREGATE AND MEN ...

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

    1. GENERAL VIEW OF ENGINE PILE OF AGGREGATE AND MEN WAITING WITH WHEELBARROWS FILLED WITH AGGREGATE. TAKE DEC. 7, 1927. - Marsh Rainbow Arch Bridge, West Eighth Street North, Newton, Jasper County, IA

  7. What favors convective aggregation and why?

    NASA Astrophysics Data System (ADS)

    Muller, Caroline; Bony, Sandrine

    2015-07-01

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

  8. Experimentally constraining the boundary conditions for volcanic ash aggregation

    NASA Astrophysics Data System (ADS)

    Kueppers, U.; Auer, B.; Cimarelli, C.; Scolamacchia, T.; Guenthel, M.; Dingwell, D. B.

    2011-12-01

    Volcanic ash is the primary product of various volcanic processes. Due to its size, ash can remain in the atmosphere for a prolonged period of time. Aggregation processes are a first-order influence on the residence time of ash in the atmosphere and its dispersion from the vent. Due to their internal structure, ash aggregates have been classified as ash pellets or accretionary lapilli. Although several concomitant factors may play a role during aggregation, there is a broad consensus that both 1) particle collision and 2) humidity are required for particles to aggregate. However, direct observation of settling aggregates and record of the boundary conditions favourable to their formation are rare, therefore limiting our understanding of the key processes that determine ash aggregates formation. Here, we present the first results from experiments aimed at reproducing ash aggregation by constraining the required boundary conditions. We used a ProCell Lab System of Glatt Ingenieurtechnik GmbH that is conventionally used for food and chemical applications. We varied the following parameters: 1) air flow speed [40-120 m3/h], 2) air temperature [30-60°C], 3) relative humidity [20-50 %], and 4) liquid droplets composition [water and 25% water glass, Na2SiO3]. The starting material (125-90 μm) is obtained by milling natural basaltic lapilli (Etna, Italy). We found that the experimental duration and the chosen conditions were not favourable for the production of stable aggregates when using water as spraying liquid. Using a 25% water-glass solution as binder we could successfully generate and investigate aggregates of up to 2 mm size. Many aggregates are spherical and resemble ash pellets. In nature, ash pellets and accretionary lapilli are the product of complex processes taking place at very different conditions (temperature, humidity, ash concentration, degree of turbulence). These experiments shed some first light on the ash agglomeration process for which direct

  9. Privileged Girls: The Place of Femininity and Femininity in Place

    ERIC Educational Resources Information Center

    Fahey, Johannah

    2014-01-01

    Constructions of femininity and attendant notions of feminism are being produced in different ways in different places around the world. This is a complicated global process that cannot be reduced to analyses that take place in nation states. This paper seeks to respond to and enhance Angela McRobbie's compelling argument about understandings…

  10. 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.

  11. Applications of aggregation theory to sustainability assessment

    DOE PAGES

    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

  12. The insanity of place.

    PubMed

    Scull, Andrew

    2004-12-01

    This paper uses English examples to scrutinize the complex interrelations of insanity and place over the past three centuries, taking as its starting point the late Erving Goffman's paper of the same title. From eighteenth-century Bedlam and the emerging trade in lunacy, through the county asylums and licensed madhouses of the nineteenth century to the return of the the mentally ill to the 'community' in the last half of the twentieth century, the place occupied by insanity has varied sharply, symbolically as well as concretely. These various techniques of containment and damage limitation must be understood as a response to the threats, symbolic and practical, that serious mental illness poses to the social order, at both the micro- and macroscopic levels of analysis.

  13. Taking Risks.

    ERIC Educational Resources Information Center

    Merson, Martha, Ed.; Reuys, Steve, Ed.

    1999-01-01

    Following an introduction on "Taking Risks" (Martha Merson), this journal contains 11 articles on taking risks in teaching adult literacy, mostly by educators in the Boston area. The following are included: "My Dreams Are Bigger than My Fears Now" (Sharon Carey); "Making a Pitch for Poetry in ABE [Adult Basic Education]" (Marie Hassett); "Putting…

  14. Pressure effects on the structure, kinetic, and thermodynamic properties of heat-induced aggregation of protein studied by FT-IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Taniguchi, Y.; Okuno, A.; Kato, M.

    2010-03-01

    Pressure can retrain the heat-induced aggregation and dissociate the heat-induced aggregates. We observed the aggregation-preventing pressure effect and the aggregates-dissociating pressure effect to characterize the heat-induced aggregation of equine serum albumin (ESA) by FT-IR spectroscopy. The results suggest the α-helical structure collapses at the beginning of heat-induced aggregation through the swollen structure, and then the rearrangement of structure to the intermolecular β-sheet takes place through partially unfolded structure. We determined the activation volume for the heat-induced aggregation (ΔV# = +93 ml/mol) and the partial molar volume difference between native state and heat-induced aggregates (ΔV=+32 ml/mol). This positive partial molar volume difference suggests that the heat-induced aggregates have larger internal voids than the native structure. Moreover, the positive volume change implies that the formation of the intermolecular β-sheet is unfavorable under high pressure.

  15. Mountain Hike North of Big Cottonwood Canyon Road, Begining at the S-Turn at Mill B., Near Hidden Falls, and Taking Trail Leading to Mt. Raymond and Other Intersting Places.

    NASA Astrophysics Data System (ADS)

    McDonald, Keith L.

    2004-11-01

    Our first objective is to leave the highway via Mill B North Fork by taking the Big Cottonwood Canyon trail that leads to Maxfield Basin, where 3 trails intersect, just s. of Mount Raymond (Elev. 10,241 ft.) the n. trail takes us down to the Mill Creek Canyon Road, at about 1 mi. (+) east of intersection with Church Park Picnic Ground road. At Maxfield Basin, again, the east trail skirts around Mt. Raymond and has another intersection with a trail running n. thru the area of Gobblers Knob (elev. 10,246 ft.), to White Fir Pass and turns w. at Bowman Fk. until it connects with Porter Fork and then the Mill Creek Road. The remaining trail at Mill A Basin, just e. of Mount Raymond, long before Gobblers Knob is seen, runs east past a spring, and connects to Butler Fork (which begins at 3.775 mi., measured along highway from Mill B, North Fork), which leads directly to Dog Lake. Evidently both Dog Lake and Lake Desolation (changing U.S. Geological Survey maps from Mount Aire, Utah to Park City West, Utah) have connected outlets, at least during certain times of the year. Following the trail s. e. (down) that follows near Summit Co. and Salt Lake County, we pass by the radio transmitters shown on Park City, West, Utah, map and finally enter the Brighton, Utah map with Scott Hill, Scott Pass, the important highway leading to Midway Reservoir, and beyond, Bloods Lake ( 9500 ft.), Clayton Peak (10,721 ft.) and Lake Lackawaxen ( 9980 ft.), our final destination showing through. One may easily walk the distance to lake Lackawaxen from Bloods Lake by staying south of the ridgecrest and by following the hollow down for a while. This completes our destination. Recall that the main roadway here was already passed over about 1/2 mile n. of Bloods Lake; this thoroughfare has its beginning at about 0.4 miles below (or North) of the Brighton Loop, where the road to city of Midway leaves the main Big Cottonwood Highway going n. and runs e., on the average, going past Midway Reservoir

  16. Taking antacids

    MedlinePlus

    ... magnesium may cause diarrhea. Brands with calcium or aluminum may cause constipation. Rarely, brands with calcium may ... you take large amounts of antacids that contain aluminum, you may be at risk for calcium loss, ...

  17. Inventories, oil shocks, and aggregate economic behavior

    NASA Astrophysics Data System (ADS)

    Herrera, Ana Maria

    This dissertation examines the relationship between oil price shocks and aggregate economic behavior in the U.S. The first chapter addresses the effects of changes in the price of crude oil on the manufacturing sector in VAR regressions and in a structural linear quadratic inventory model. It finds that oil price increases lead to reductions in manufacturing activity while oil price falls are not followed by booms. This asymmetry in the response of the manufacturing activity, the changes in the composition of the demand, and the large variations in sales of key investment and consumption goods favor a multi-channel transmission mechanism. The analysis shows that differences in the response of the various industrial sectors are determined by the cost structure of the industry as well as by the dynamics of the demand, cost and oil shocks. Positive oil price shocks are first transmitted from the transportation equipment industry to sectors such as primary metals products, rubber and plastics and textiles, later affecting the remaining sectors and the aggregates. In the short run inventories act as a buffer however, one and a half years after the shock significant production cuts do take place. Sluggishness in the response of aggregate output can be accounted by the behavior of inventories as well as by the time lags implied in the propagation from one industry to the remaining sectors and the aggregate. The second chapter studies the role of oil prices and monetary policy in accounting for business cycles in an identified VAR framework. It finds that the slowdown in GDP growth that follows an oil shock can not be solely explained by the response of the Fed's monetary policy. An "exogenous" monetary policy that holds the fed funds rate fixed would exert a large expansionary effect. Nevertheless, conditional on this policy, the reduction in economic activity persists and the price level increases leading to a sharp reduction in the short-term interest rate. In addition

  18. What is taking place in science classrooms?: A case study analysis of teaching and learning in seventh-grade science of one Alabama school and its impact on African American student learning

    NASA Astrophysics Data System (ADS)

    Norman, Lashaunda Renea

    This qualitative case study investigated the teaching strategies that improve science learning of African American students. This research study further sought the extent the identified teaching strategies that are used to improve African American science learning reflect culturally responsive teaching. Best teaching strategies and culturally responsive teaching have been researched, but there has been minimal research on the impact that both have on science learning, with an emphasis on the African American population. Consequently, the Black-White achievement gap in science persists. The findings revealed the following teaching strategies have a positive impact on African American science learning: (a) lecture-discussion, (b) notetaking, (c) reading strategies, (d) graphic organizers, (e) hands-on activities, (f) laboratory experiences, and (g) cooperative learning. Culturally responsive teaching strategies were evident in the seventh-grade science classrooms observed. Seven themes emerged from this research data: (1) The participating teachers based their research-based teaching strategies used in the classroom on all of the students' learning styles, abilities, attitudes towards science, and motivational levels about learning science, with no emphasis on the African American student population; (2) The participating teachers taught the state content standards simultaneously using the same instructional model daily, incorporating other content areas when possible; (3) The participating African American students believed their seventh-grade science teachers used a variety of teaching strategies to ensure science learning took place, that science learning was fun, and that science learning was engaging; (4) The participating African American students genuinely liked their teacher; (5) The participating African American students revealed high self-efficacy; (6) The African American student participants' parents value education and moved to Success Middle School

  19. Taking Turns

    ERIC Educational Resources Information Center

    Hopkins, Brian

    2010-01-01

    Two people take turns selecting from an even number of items. Their relative preferences over the items can be described as a permutation, then tools from algebraic combinatorics can be used to answer various questions. We describe each person's optimal selection strategies including how each could make use of knowing the other's preferences. We…

  20. Double Take

    ERIC Educational Resources Information Center

    Educational Leadership, 2011

    2011-01-01

    This paper begins by discussing the results of two studies recently conducted in Australia. According to the two studies, taking a gap year between high school and college may help students complete a degree once they return to school. The gap year can involve such activities as travel, service learning, or work. Then, the paper presents links to…

  1. 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

  2. Brazilian physicists take centre stage

    NASA Astrophysics Data System (ADS)

    Curtis, Susan

    2014-06-01

    With the FIFA World Cup taking place in Brazil this month, Susan Curtis travels to South America's richest nation to find out how its physicists are exploiting recent big increases in science funding.

  3. Mechanisms and Kinetics of Amyloid Aggregation Investigated by a Phenomenological Coarse-Grained Model

    NASA Astrophysics Data System (ADS)

    Magno, Andrea; Pellarin, Riccardo; Caflisch, Amedeo

    Amyloid fibrils are ordered polypeptide aggregates that have been implicated in several neurodegenerative pathologies, such as Alzheimer's, Parkinson's, Huntington's, and prion diseases, [1, 2] and, more recently, also in biological functionalities. [3, 4, 5] These findings have paved the way for a wide range of experimental and computational studies aimed at understanding the details of the fibril-formation mechanism. Computer simulations using low-resolution models, which employ a simplified representation of protein geometry and energetics, have provided insights into the basic physical principles underlying protein aggregation in general [6, 7, 8] and ordered amyloid aggregation. [9, 10, 11, 12, 13, 14, 15] For example, Dokholyan and coworkers have used the Discrete Molecular Dynamics method [16, 17] to shed light on the mechanisms of protein oligomerization [18] and the conformational changes that take place in proteins before the aggregation onset. [19, 20] One challenging observation, which is difficult to observe by computer simulations, is the wide range of aggregation scenarios emerging from a variety of biophysical measurements. [21, 22] Atomistic models have been employed to study the conformational space of amyloidogenic polypeptides in the monomeric state, [23, 24, 25] the very initial steps of amyloid formation, [26, 27, 28, 29, 30, 31, 32] and the structural stability of fibril models. [33, 34, 35) However, all-atom simulations of the kinetics of fibril formation are beyond what can be done with modern computers.

  4. Surfactant induced aggregation behavior of Merocyanine-540 adsorbed on polymer coated positively charged gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Das, K.; Uppal, A.; Saini, R. K.

    2016-01-01

    Surfactant induced aggregation behavior of Merocyanine 540 adsorbed on polymer (PDD) coated gold nanoparticles (AuNP) is reported. The absorption band of the dye shifts to higher energy in the presence of free polymer and polymer coated AuNP implying aggregation. Addition of a negatively charged surfactant (SDS) induces multiple bands in the extinction spectrum of the dye adsorbed on nanoparticle surface. The highest (460 nm) and lowest (564 nm) energy bands of the dye become prominent at 10 and >50 μM SDS concentrations respectively (dye: 10 μM; AuNP: 100-200 pM). Based on earlier results the high energy band is likely to originate from dye aggregates and the low energy band is likely to originate from dye monomers. This is attributed to the interplay between polymer-surfactant and polymer-dye interactions at the AuNP surface. The extinction spectra of dye adsorbed at AuNP surface remain unaffected in the presence of a positively charged (CTAB) or a neutral surfactant (Tx-100), at low surfactant concentrations. However at higher surfactant concentrations (>60 μM) dye aggregation takes place which is attributed to dye-surfactant interactions. The fluorescence intensity of the dye quenched significantly but its lifetime increased in the presence of polymer coated AuNP. This is attributed to aggregation and reduction in the photoisomerization rate of the dye adsorbed on AuNP surface.

  5. Dynamics of proteins aggregation. I. Universal scaling in unbounded media

    NASA Astrophysics Data System (ADS)

    Zheng, Size; Javidpour, Leili; Shing, Katherine S.; Sahimi, Muhammad

    2016-10-01

    It is well understood that in some cases proteins do not fold correctly and, depending on their environment, even properly-folded proteins change their conformation spontaneously, taking on a misfolded state that leads to protein aggregation and formation of large aggregates. An important factor that contributes to the aggregation is the interactions between the misfolded proteins. Depending on the aggregation environment, the aggregates may take on various shapes forming larger structures, such as protein plaques that are often toxic. Their deposition in tissues is a major contributing factor to many neuro-degenerative diseases, such as Alzheimer's, Parkinson's, amyotrophic lateral sclerosis, and prion. This paper represents the first part in a series devoted to molecular simulation of protein aggregation. We use the PRIME, a meso-scale model of proteins, together with extensive discontinuous molecular dynamics simulation to study the aggregation process in an unbounded fluid system, as the first step toward MD simulation of the same phenomenon in crowded cellular environments. Various properties of the aggregates have been computed, including dynamic evolution of aggregate-size distribution, mean aggregate size, number of peptides that contribute to the formation of β sheets, number of various types of hydrogen bonds formed in the system, radius of gyration of the aggregates, and the aggregates' diffusivity. We show that many of such quantities follow dynamic scaling, similar to those for aggregation of colloidal clusters. In particular, at long times the mean aggregate size S(t) grows with time as, S(t) ˜ tz, where z is the dynamic exponent. To our knowledge, this is the first time that the qualitative similarity between aggregation of proteins and colloidal aggregates has been pointed out.

  6. A Case Study of How Teaching Practice Process Takes Place

    ERIC Educational Resources Information Center

    Yalin Ucar, Meltem

    2012-01-01

    The process of "learning" carries an important role in the teaching practice which provides teacher candidates with professional development. Being responsible for the learning experiences in that level, cooperating teacher, teacher candidate, mentor and practice school are the important variables which determine the quality of the teaching…

  7. Using Personalized Education to Take the Place of Standardized Education

    ERIC Educational Resources Information Center

    Gao, Pengyu

    2014-01-01

    Economic model has been greatly shifted from labor demanding to innovation demanding, which requires education system has to produce creative people. This paper illustrates how traditional education model accrued and developed based on satisfying the old economic model for labor demanding but did not meet the new social requirement for innovation…

  8. Site-dependence of van der Waals interaction explains exciton spectra of double-walled tubular J-aggregates.

    PubMed

    Megow, Jörg; Röhr, Merle I S; Schmidt am Busch, Marcel; Renger, Thomas; Mitrić, Roland; Kirstein, Stefan; Rabe, Jürgen P; May, Volkhard

    2015-03-14

    The simulation of the optical properties of supramolecular aggregates requires the development of methods, which are able to treat a large number of coupled chromophores interacting with the environment. Since it is currently not possible to treat large systems by quantum chemistry, the Frenkel exciton model is a valuable alternative. In this work we show how the Frenkel exciton model can be extended in order to explain the excitonic spectra of a specific double-walled tubular dye aggregate explicitly taking into account dispersive energy shifts of ground and excited states due to van der Waals interaction with all surrounding molecules. The experimentally observed splitting is well explained by the site-dependent energy shift of molecules placed at the inner or outer side of the double-walled tube, respectively. Therefore we can conclude that inclusion of the site-dependent dispersive effect in the theoretical description of optical properties of nanoscaled dye aggregates is mandatory. PMID:25620460

  9. High-resolution single-molecule fluorescence imaging of zeolite aggregates within real-life fluid catalytic cracking particles.

    PubMed

    Ristanović, Zoran; Kerssens, Marleen M; Kubarev, Alexey V; Hendriks, Frank C; Dedecker, Peter; Hofkens, Johan; Roeffaers, Maarten B J; Weckhuysen, Bert M

    2015-02-01

    Fluid catalytic cracking (FCC) is a major process in oil refineries to produce gasoline and base chemicals from crude oil fractions. The spatial distribution and acidity of zeolite aggregates embedded within the 50-150 μm-sized FCC spheres heavily influence their catalytic performance. Single-molecule fluorescence-based imaging methods, namely nanometer accuracy by stochastic chemical reactions (NASCA) and super-resolution optical fluctuation imaging (SOFI) were used to study the catalytic activity of sub-micrometer zeolite ZSM-5 domains within real-life FCC catalyst particles. The formation of fluorescent product molecules taking place at Brønsted acid sites was monitored with single turnover sensitivity and high spatiotemporal resolution, providing detailed insight in dispersion and catalytic activity of zeolite ZSM-5 aggregates. The results point towards substantial differences in turnover frequencies between the zeolite aggregates, revealing significant intraparticle heterogeneities in Brønsted reactivity.

  10. Site-dependence of van der Waals interaction explains exciton spectra of double-walled tubular J-aggregates.

    PubMed

    Megow, Jörg; Röhr, Merle I S; Schmidt am Busch, Marcel; Renger, Thomas; Mitrić, Roland; Kirstein, Stefan; Rabe, Jürgen P; May, Volkhard

    2015-03-14

    The simulation of the optical properties of supramolecular aggregates requires the development of methods, which are able to treat a large number of coupled chromophores interacting with the environment. Since it is currently not possible to treat large systems by quantum chemistry, the Frenkel exciton model is a valuable alternative. In this work we show how the Frenkel exciton model can be extended in order to explain the excitonic spectra of a specific double-walled tubular dye aggregate explicitly taking into account dispersive energy shifts of ground and excited states due to van der Waals interaction with all surrounding molecules. The experimentally observed splitting is well explained by the site-dependent energy shift of molecules placed at the inner or outer side of the double-walled tube, respectively. Therefore we can conclude that inclusion of the site-dependent dispersive effect in the theoretical description of optical properties of nanoscaled dye aggregates is mandatory.

  11. Influence of polydisperse distributions of both primary particle and aggregate size on soot temperature in low-fluence LII

    NASA Astrophysics Data System (ADS)

    Liu, F.; Yang, M.; Hill, F. A.; Snelling, D. R.; Smallwood, G. J.

    2006-06-01

    An improved aggregate-based low-fluence laser-induced incandescence (LII) model has been developed. The shielding effect in heat conduction between aggregated soot particles and the surrounding gas was modeled using the concept of the equivalent heat transfer sphere. The diameter of such an equivalent sphere was determined from direct simulation Monte Carlo calculations in the free molecular regime as functions of the aggregate size and the thermal accommodation coefficient of soot. Both the primary soot particle diameter and the aggregate size distributions are assumed to be lognormal. The effective temperature of a soot particle ensemble containing different primary particle diameters and aggregate sizes in the laser probe volume was calculated based on the ratio of the total thermal radiation intensities of soot particles at 400 and 780 nm to simulate the experimentally measured soot particle temperature using two-color optical pyrometry. The effect of primary particle diameter polydispersity is in general important and should be considered. The effect of aggregate size polydispersity is relatively unimportant when the heat conduction between the primary particles and the surrounding gas takes place in the free-molecular regime; however, it starts to become important when the heat conduction process occurs in the near transition regime. The model developed in this study was also applied to the re-determination of the thermal accommodation coefficient of soot in an atmospheric pressure laminar ethylene diffusion flame.

  12. 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

  13. Places for Pedagogies, Pedagogies for Places

    ERIC Educational Resources Information Center

    Duhn, Iris

    2012-01-01

    Working with an understanding of assemblage as the ad hoc groupings of vibrant materials and elements, this article argues that conceptualizing place as an assemblage opens possibilities for bridging the gap between subjects and objects that continue to structure pedagogy. Considering "place" as an assemblage of humans and their multiple "others"…

  14. 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.

  15. 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)

  16. Universal power-law and partial condensation in aggregation-chipping processes

    NASA Astrophysics Data System (ADS)

    Yamamoto, Hiroshi; Ohtsuki, Toshiya

    2010-06-01

    The asymptotic behaviour of a distribution function P(X) for X clusters is investigated in aggregation-chipping processes, where aggregation and chipping off of a finite unit of size less than L take place simultaneously. Numerical simulations show that above a certain threshold ⟨X⟩c of an average cluster size, the system exhibits partial condensation where one condensed cluster coexists with a universal power-law distribution with the exponent -5/2 . The critical value ⟨X⟩c is calculated and turns out to increase monotonously with L . The z -transform technique is used to analyze the case L=2 in detail. Obtained results agree well with numerical ones. Finally, universality of the asymptotic power law is discussed for general cases. It becomes evident that universality holds as long as the size of chipped off unit is finite.

  17. Re(Place) Your Typical Writing Assignment: An Argument for Place-Based Writing

    ERIC Educational Resources Information Center

    Jacobs, Elliot

    2011-01-01

    Place-based writing affords students an opportunity to write meaningfully about themselves, grounded in a place that they know. Place-based writing is versatile and can be additive--taking just a week or two within a semester of different projects--or transformative, if positioned as the theme for an entire course. If students can learn to write…

  18. Physical, morphological and functional differences between ph 5.8 and 7.4 aggregates of the Alzheimer's amyloid peptide Abeta.

    PubMed

    Wood, S J; Maleeff, B; Hart, T; Wetzel, R

    1996-03-15

    The Alzheimer's amyloid peptide Abeta(1-40) generates a turbid, Congo re-binding aggregation reaction product within minutes when incubated in the pH range 5 to 6. At pH 7.4, Abeta forms little or no aggregate in this time frame, requiring hours or days, rather than minutes, to complete fibril formation. The pH 5.8 aggregates are not amyloid fibrils, but rather appear in electron micrographs as a mixture of larger particles of different morphologies. These aggregates differ from classical fibrils by a number of other measures. Per mass of peptide aggregated, the pH 5.8 product binds less Congo red and thioflavin T than does aggregate grow in unstirred reactions at pH 7.4. Both the pH 5.8 and 7.4 aggregates exhibit light scattering at 90 degrees. However, while the pH 5.8 aggregate is visible in suspension by the light microscopy, and exhibits turbidity at 405 nm, the fibrils grown at pH 7.4 in an unstirred reaction are transparent. The two aggregate types do not interconvert in pH shift experiments. Most dramatically, and in contrast to fibrils grown at pH 7.4, the turbid aggregate generated at pH 5.8 is incapable of seeding fibril growth at pH 7.4. Although proteolytic processing of betaAPP to generate Abeta probably takes place in a low pH compartment of the cell, our results suggest that fibril formation is not likely to be initiated in such an environment.

  19. 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.

  20. The aggregation efficiency of very fine volcanic ash

    NASA Astrophysics Data System (ADS)

    Del Bello, E.; Taddeucci, J.; Scarlato, P.

    2013-12-01

    Explosive volcanic eruptions can discharge large amounts of very small sized pyroclasts (under 0.090 mm) into the atmosphere that may cause problems to people, infrastructures and environment. The transport and deposition of fine ash are ruled by aggregation that causes premature settling of fine ash and, as consequence, significantly reduces the concentration of airborne material over long distances. Parameterizing the aggregation potential of fine ash is then needed to provide accurate modelling of ash transport and deposition from volcanic plumes. Here we present the first results of laboratory experiments investigating the aggregation efficiency of very fine volcanic particles. Previous laboratory experiments have shown that collision kinetic and relative humidity provide the strongest effect on aggregation behaviour but were only limited to particles with size > 0.125 mm. In our work, we focus on natural volcanic ash at ambient humidity with particles size < 0.090 mm, by taking into account the effect of grain size distribution on aggregation potential. Two types of ash were used in our experiments: fresh ash, collected during fall-out from a recent plume-forming eruption at Sakurajima (Japan -July 2013) and old ash, collected from fall-out tephra deposits at Campi Flegrei (Italy, ca. 10 ka), to account for the different chemical composition and morphoscopic effects of altered ash on aggregation efficiency. Total samples were hand sieved to obtain three classes with unimodal grain size distributions (<0.090 mm, <0.063 mm, <0.032 mm). Bimodal grain size distributions were also obtained by mixing the three classes in different proportions. During each experiments, particles were sieved from the top of a transparent tank where a fan, placed at the bottom, allows turbulent dispersion of particles. Collision and sticking of particles on a vertical glass slide were filmed with a high speed cameras at 6000 fps. Our lenses arrangement provide high image resolution

  1. Complex Behavior of Aqueous α-Cyclodextrin Solutions. Interfacial Morphologies Resulting from Bulk Aggregation.

    PubMed

    Hernandez-Pascacio, Jorge; Piñeiro, Ángel; Ruso, Juan M; Hassan, Natalia; Campbell, Richard A; Campos-Terán, José; Costas, Miguel

    2016-07-01

    The spontaneous aggregation of α-cyclodextrin (α-CD) molecules in the bulk aqueous solution and the interactions of the resulting aggregates at the liquid/air interface have been studied at 283 K using a battery of techniques: transmission electron microscopy, dynamic light scattering, dynamic surface tensiometry, Brewster angle microscopy, neutron reflectometry, and ellipsometry. We show that α-CD molecules spontaneously form aggregates in the bulk that grow in size with time. These aggregates adsorb to the liquid/air interface with their size in the bulk determining the adsorption rate. The material that reaches the interface coalesces laterally to form two-dimensional domains on the micrometer scale with a layer thickness on the nanometer scale. These processes are affected by the ages of both the bulk and the interface. The interfacial layer formed is not in fast dynamic equilibrium with the subphase as the resulting morphology is locked in a kinetically trapped state. These results reveal a surprising complexity of the parallel physical processes taking place in the bulk and at the interface of what might have seemed initially like a simple system.

  2. Complex Behavior of Aqueous α-Cyclodextrin Solutions. Interfacial Morphologies Resulting from Bulk Aggregation.

    PubMed

    Hernandez-Pascacio, Jorge; Piñeiro, Ángel; Ruso, Juan M; Hassan, Natalia; Campbell, Richard A; Campos-Terán, José; Costas, Miguel

    2016-07-01

    The spontaneous aggregation of α-cyclodextrin (α-CD) molecules in the bulk aqueous solution and the interactions of the resulting aggregates at the liquid/air interface have been studied at 283 K using a battery of techniques: transmission electron microscopy, dynamic light scattering, dynamic surface tensiometry, Brewster angle microscopy, neutron reflectometry, and ellipsometry. We show that α-CD molecules spontaneously form aggregates in the bulk that grow in size with time. These aggregates adsorb to the liquid/air interface with their size in the bulk determining the adsorption rate. The material that reaches the interface coalesces laterally to form two-dimensional domains on the micrometer scale with a layer thickness on the nanometer scale. These processes are affected by the ages of both the bulk and the interface. The interfacial layer formed is not in fast dynamic equilibrium with the subphase as the resulting morphology is locked in a kinetically trapped state. These results reveal a surprising complexity of the parallel physical processes taking place in the bulk and at the interface of what might have seemed initially like a simple system. PMID:27299803

  3. How to Cope with Sheltering in Place

    MedlinePlus

    ... your own or a relative’s home, school, or work. Sheltering in place may be required because of an emergency such ... things to keep yourself calm while sheltering in place. Relax your body often by doing things that work for you—take deep breaths, stretch, meditate or ...

  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. Place and Pedagogy

    ERIC Educational Resources Information Center

    Orr, David

    2013-01-01

    David Orr's classic article links education to living in the outdoors and studying all disciplines through the unifying lens of place. Pedagogy of place counters abstraction, it is the natural world embodying principles of learning that involve direct observation, investigation, experimentation, and manual skills. Place is the laboratory providing…

  6. Cell aggregation and sedimentation.

    PubMed

    Davis, R H

    1995-01-01

    The aggregation of cells into clumps or flocs has been exploited for decades in such applications as biological wastewater treatment, beer brewing, antibiotic fermentation, and enhanced sedimentation to aid in cell recovery or retention. More recent research has included the use of cell aggregation and sedimentation to selectively separate subpopulations of cells. Potential biotechnological applications include overcoming contamination, maintaining plasmid-bearing cells in continuous fermentors, and selectively removing nonviable hybridoma cells from perfusion cultures.

  7. A woman's rightful place?

    PubMed

    1993-04-01

    Rural development projects in sub-Saharan Africa tend not to succeed because they do not consider women's role and their significance, even though women constitute 70% of agricultural workers, 80% of food producers, 100% of people who prepare meals, and 60-90% do food marketing. Development specialists ignore women because they are not involved in political activities and in decision making. As long as women and women's contributions are not considered, rural development projects will remain inefficient and development will not take place. Thus, projects must include women as agents and beneficiaries of development in key sectors of the economy. Rural development specialists must also consider the effect male labor emigration has on rural women. For example, drought has forced many men to leave their villages, leaving a work force consisting of 95% women to fight desertification. All too often, women have no or limited land ownership rights, thereby keeping them from improving the land, e.g., planting perennial fruit crops. They also tend to be hired hands rather than food producers. They cannot obtain bank loans because they do not own land, and because they are often illiterate (over 90% female illiteracy in 28 African countries), they can neither understand nor complete bank loan forms. Rural development projects further alienate women by aiming training programs to men or by using male agricultural extension agents. Women react to this alienation by rejecting projects that do not benefit them and follow more profitable activities which sometimes interfere with projects. Thus, rural development programs need to invest in women to ensure viable and efficient sustainable development.

  8. Processes in resonant domains of metal nanoparticle aggregates and optical nonlinearity of aggregates in pulsed laser fields

    NASA Astrophysics Data System (ADS)

    Gavrilyuk, A. P.; Karpov, S. V.

    2009-09-01

    Optical nonlinearities in aggregates of nanoparticles formed in silver hydrosols (SHs) are studied under pico- and nanosecond pulsed laser excitation. The dependence of the nonlinear refractive index n 2 on the degree of hydrosol aggregation is studied experimentally at the wavelength λ=1.064 μm. It is found that n 2 changes sign when the degree of hydrosol aggregation is increased. Various physical effects occurring in resonant domains of the aggregates are analyzed using a simple physical model of two bound silver nanoparticles. The theory takes into account thermal, elastic, electrostatic, and light-induced effects. Experimental results are discussed in the context of this theory.

  9. Fibronectin Aggregation and Assembly

    PubMed Central

    Ohashi, Tomoo; Erickson, Harold P.

    2011-01-01

    The mechanism of fibronectin (FN) assembly and the self-association sites are still unclear and contradictory, although the N-terminal 70-kDa region (I1–9) is commonly accepted as one of the assembly sites. We previously found that I1–9 binds to superfibronectin, which is an artificial FN aggregate induced by anastellin. In the present study, we found that I1–9 bound to the aggregate formed by anastellin and a small FN fragment, III1–2. An engineered disulfide bond in III2, which stabilizes folding, inhibited aggregation, but a disulfide bond in III1 did not. A gelatin precipitation assay showed that I1–9 did not interact with anastellin, III1, III2, III1–2, or several III1–2 mutants including III1–2KADA. (In contrast to previous studies, we found that the III1–2KADA mutant was identical in conformation to wild-type III1–2.) Because I1–9 only bound to the aggregate and the unfolding of III2 played a role in aggregation, we generated a III2 domain that was destabilized by deletion of the G strand. This mutant bound I1–9 as shown by the gelatin precipitation assay and fluorescence resonance energy transfer analysis, and it inhibited FN matrix assembly when added to cell culture. Next, we introduced disulfide mutations into full-length FN. Three disulfide locks in III2, III3, and III11 were required to dramatically reduce anastellin-induced aggregation. When we tested the disulfide mutants in cell culture, only the disulfide bond in III2 reduced the FN matrix. These results suggest that the unfolding of III2 is one of the key factors for FN aggregation and assembly. PMID:21949131

  10. 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

  11. 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.

  12. Individual Preferences and Social Interactions Determine the Aggregation of Woodlice

    PubMed Central

    Devigne, Cédric; Broly, Pierre; Deneubourg, Jean-Louis

    2011-01-01

    Background The aggregation of woodlice in dark and moist places is considered an adaptation to land life and most studies are focused on its functionality or on the behavioural mechanisms related to the individual's response to abiotic factors. Until now, no clear experimental demonstration was available about aggregation resulting from inter-attraction between conspecifics. Methodology/Main Findings We present the dynamics of aggregation, not previously described in detail in literature, as being independent of the experimental conditions: homogeneous and heterogeneous environments with identical or different shelters. Indeed whatever these conditions, the aggregation is very quick. In less than 10 minutes more than 50% of woodlice were aggregated in several small groups in the homogeneous environment or under shelters in the heterogeneous environment. After this fast aggregation, woodlice progressively moved into a single aggregate or under one shelter. Conclusions/Significance Here we show for the first time that aggregation in woodlice implies a strong social component and results from a trade-off between individual preferences and inter-attraction between individuals. Moreover, our results reveal that the response to the heterogeneities affects only the location of the aggregates and not the level of aggregation, and demonstrate the strong inter-attraction between conspecifics which can outweigh individual preferences. This inter-attraction can lead to situations that could seem sub-optimal. PMID:21364761

  13. Thermodynamic evidence for Ca2+-mediated self-aggregation of Lewis X gold glyconanoparticles. A model for cell adhesion via carbohydrate-carbohydrate interaction.

    PubMed

    de la Fuente, Jesús M; Eaton, Peter; Barrientos, Africa G; Menéndez, Margarita; Penadés, Soledad

    2005-05-01

    Thermodynamic evidence for the selective Ca(2+)-mediated self-aggregation via carbohydrate-carbohydrate interactions of gold glyconanoparticles functionalized with the disaccharides lactose (lacto-Au) and maltose (malto-Au), or the biologically relevant trisaccharide Lewis X (Le(X)-Au), was obtained by isothermal titration calorimetry. The aggregation process was also directly visualized by atomic force microscopy. It was shown in the case of the trisaccharide Lewis X that the Ca(2+)-mediated aggregation is a slow process that takes place with a decrease in enthalpy of 160 +/- 30 kcal mol(-)(1), while the heat evolved in the case of lactose and maltose glyconanoparticles was very low and thermal equilibrium was quickly achieved. Measurements in the presence of Mg(2+) and Na(+) cations confirm the selectivity for Ca(2+) of Le(X)-Au glyconanoparticles. The relevance of this result to cell-cell adhesion process mediated by carbohydrate-carbohydrate interactions is discussed. PMID:15853323

  14. Thermodynamic evidence for Ca2+-mediated self-aggregation of Lewis X gold glyconanoparticles. A model for cell adhesion via carbohydrate-carbohydrate interaction.

    PubMed

    de la Fuente, Jesús M; Eaton, Peter; Barrientos, Africa G; Menéndez, Margarita; Penadés, Soledad

    2005-05-01

    Thermodynamic evidence for the selective Ca(2+)-mediated self-aggregation via carbohydrate-carbohydrate interactions of gold glyconanoparticles functionalized with the disaccharides lactose (lacto-Au) and maltose (malto-Au), or the biologically relevant trisaccharide Lewis X (Le(X)-Au), was obtained by isothermal titration calorimetry. The aggregation process was also directly visualized by atomic force microscopy. It was shown in the case of the trisaccharide Lewis X that the Ca(2+)-mediated aggregation is a slow process that takes place with a decrease in enthalpy of 160 +/- 30 kcal mol(-)(1), while the heat evolved in the case of lactose and maltose glyconanoparticles was very low and thermal equilibrium was quickly achieved. Measurements in the presence of Mg(2+) and Na(+) cations confirm the selectivity for Ca(2+) of Le(X)-Au glyconanoparticles. The relevance of this result to cell-cell adhesion process mediated by carbohydrate-carbohydrate interactions is discussed.

  15. The value of place

    NASA Astrophysics Data System (ADS)

    Dentzau, Michael W.

    2014-03-01

    This commentary seeks to expand the dialogue on place-based science education presented in Katie Lynn Brkich's article, where the connections fifth grade students make between their formal earth science curriculum and their lived experiences are highlighted. The disconnect between the curriculum the students are offered and their immediate environment is clear, and we are presented with examples of how they strive to make connections between the content and what they are familiar with—namely their surroundings. "Place" is identified as a term with complex meanings and interpretations, even in the scope of place-based science education, and understanding how the term is used in any given scenario is essential to understanding the implications of place-based education. Is place used as a location, locale or a sense of place? To understand "place" is to acknowledge that for the individual, it is highly situational, cultural and personal. It is just such attributes that make place-based education appealing, and potentially powerful, pedagogically on one hand, yet complex for implementation on the other. The argument is posed that place is particularly important in the context of education about the environment, which in its simplest manifestation, connects formal science curriculum to resources that are local and tangible to students. The incorporation of place in such a framework seeks to bridge the gap between formal school science subjects and students' lived experiences, yet acknowledges the tensions that can arise between accommodating place meanings and the desire to acculturate students into the language of the scientific community. The disconnect between guiding policy frameworks and the reality of the Next Generation Science Standards is addressed opening an avenue for further discussion of the importance of socio-cultural frameworks of science learning in an ever increasing era of accountability.

  16. Adsorption-induced reversible colloidal aggregation

    NASA Astrophysics Data System (ADS)

    Law, B. M.; Petit, J.-M.; Beysens, D.

    1998-05-01

    Reversible colloidal aggregation in binary liquid mixtures has been studied for a number of years. As the phase separation temperature of the liquid mixture is approached the thickness of an adsorption layer around the colloidal particles increases. Beysens et al. [Phys. Rev. Lett. 54, 2123 (1985); Ber. Bunsenges. Phys. Chem. 98, 382 (1994)] have demonstrated experimentally that this adsorption layer is intimately connected with the aggregation of the colloidal particles; however, no definitive theory has been available that can explain all of the experimental observations. In a recent work [J.-M. Petit, B. M. Law, and D. Beysens, J. Colloid Interface Sci. (to be published)] we have extended and improved the Derjaguin-Landau-Verwey-Overbeek theory of colloidal aggregation [E. J. W. Verwey and J. Th. G. Overbeek, Theory of the Stability of Lyophobic Colloids (Elsevier, New York, 1948)] by taking into account the presence of an adsorption layer and by more realistically modeling the attractive dispersion interactions using the Dzyaloshinskii-Lifshitz-Pitaevskii theory [Adv. Phys. 10, 165 (1961)]. In the present paper we apply this theory to a lutidine-water mixture containing a small volume fraction of silica colloidal particles. We demonstrate that the theory can quantitatively account for many of the experimentally observed features such as the characteristics of the aggregated state, the general shape of the aggregation line, and the temperature dependence of the second virial coefficient.

  17. 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.

  18. Place as Library?

    ERIC Educational Resources Information Center

    Davenport, Nancy

    2006-01-01

    Digital technology is redrawing the library's blueprint. Planners are thinking in new ways about how to design libraries as places for learning rather than primarily as storehouses of information. This thinking has given rise to much discussion--and to many publications--about the "library as place." In this article, the author asks why not also…

  19. The Case for Place

    ERIC Educational Resources Information Center

    Thomas, Lisa Carlucci

    2012-01-01

    Bookstores, record stores, libraries, Facebook: these places--both physical and virtual--demonstrate an established and essential purpose as centers of community, expertise, convenience, immediacy, and respect. Yet as digital, mobile, and social shifts continue to transform culture and interactions, these spaces and places transform, too.…

  20. Teaching Bodies in Place

    ERIC Educational Resources Information Center

    Jones, Stephanie; Woglom, James F.

    2013-01-01

    Background/Context: This piece draws on literature in justice-oriented teacher education, feminist pedagogy, and postmodern notions of bodies and place to make sense of data generated from a three-year study of an undergraduate teacher education course. A feminist lens was used to engage a body- and place-focused pedagogy that aimed to engage…

  1. Understanding Place Value

    ERIC Educational Resources Information Center

    Cooper, Linda L.; Tomayko, Ming C.

    2011-01-01

    Developing an understanding of place value and the base-ten number system is considered a fundamental goal of the early primary grades. For years, teachers have anecdotally reported that students struggle with place-value concepts. Among the common errors cited are misreading such numbers as 26 and 62 by seeing them as identical in meaning,…

  2. Schooling Out of Place

    ERIC Educational Resources Information Center

    McConaghy, Cathryn

    2006-01-01

    Education in rural communities is an interesting site for an analysis of the relationship between place and the cultural politics of schooling. In particular the movements of people, ideas and practices to and from, and also within, rural places suggest the need for theorizing on rural education to consider the relevance of new mobility…

  3. 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.

  4. Crowdsourcing a Collective Sense of Place.

    PubMed

    Jenkins, Andrew; Croitoru, Arie; Crooks, Andrew T; Stefanidis, Anthony

    2016-01-01

    Place can be generally defined as a location that has been assigned meaning through human experience, and as such it is of multidisciplinary scientific interest. Up to this point place has been studied primarily within the context of social sciences as a theoretical construct. The availability of large amounts of user-generated content, e.g. in the form of social media feeds or Wikipedia contributions, allows us for the first time to computationally analyze and quantify the shared meaning of place. By aggregating references to human activities within urban spaces we can observe the emergence of unique themes that characterize different locations, thus identifying places through their discernible sociocultural signatures. In this paper we present results from a novel quantitative approach to derive such sociocultural signatures from Twitter contributions and also from corresponding Wikipedia entries. By contrasting the two we show how particular thematic characteristics of places (referred to herein as platial themes) are emerging from such crowd-contributed content, allowing us to observe the meaning that the general public, either individually or collectively, is assigning to specific locations. Our approach leverages probabilistic topic modelling, semantic association, and spatial clustering to find locations are conveying a collective sense of place. Deriving and quantifying such meaning allows us to observe how people transform a location to a place and shape its characteristics. PMID:27050432

  5. Crowdsourcing a Collective Sense of Place

    PubMed Central

    Jenkins, Andrew; Croitoru, Arie; Crooks, Andrew T.; Stefanidis, Anthony

    2016-01-01

    Place can be generally defined as a location that has been assigned meaning through human experience, and as such it is of multidisciplinary scientific interest. Up to this point place has been studied primarily within the context of social sciences as a theoretical construct. The availability of large amounts of user-generated content, e.g. in the form of social media feeds or Wikipedia contributions, allows us for the first time to computationally analyze and quantify the shared meaning of place. By aggregating references to human activities within urban spaces we can observe the emergence of unique themes that characterize different locations, thus identifying places through their discernible sociocultural signatures. In this paper we present results from a novel quantitative approach to derive such sociocultural signatures from Twitter contributions and also from corresponding Wikipedia entries. By contrasting the two we show how particular thematic characteristics of places (referred to herein as platial themes) are emerging from such crowd-contributed content, allowing us to observe the meaning that the general public, either individually or collectively, is assigning to specific locations. Our approach leverages probabilistic topic modelling, semantic association, and spatial clustering to find locations are conveying a collective sense of place. Deriving and quantifying such meaning allows us to observe how people transform a location to a place and shape its characteristics. PMID:27050432

  6. Sharing Knowledge About Places as Community Building

    NASA Astrophysics Data System (ADS)

    Willis, Katharine S.; O'Hara, Kenton; Giles, Thierry; Marianek, Mike

    Our experience of places is one that goes hand-in-hand with social exchange. It is rare that we visit a place purely to experience it as an isolated encounter with a physical setting. Instead, we visit places in groups, use a myriad of ways to tell others about the experience, and we often seek out and take pleasure from encounters with local people in the setting. Our experience of place is embedded within a social framework for sharing knowledge. In this chapter, we discuss the motivations for sharing place-based knowledge and how this can contribute to community building. We then proceed to review three projects that create platforms for knowledge exchange and discuss their different approaches. This is followed by a discussion on the range of practices for sharing knowledge about places and in particular those that support social frameworks in a community setting. In conclusion, we propose directions for future work in the area.

  7. Using inclusion complexes with cyclodextrins to explore the aggregation behavior of a ruthenium metallosurfactant.

    PubMed

    Iza, Nerea; Guerrero-Martínez, Andrés; Tardajos, Gloria; Ortiz, María José; Palao, Eduardo; Montoro, Teresa; Radulescu, Aurel; Dreiss, Cécile A; González-Gaitano, Gustavo

    2015-03-10

    The aggregation behavior of a chiral metallosurfactant, bis(2,2'-bipyridine)(4,4'-ditridecyl-2,2'-bipyridine)ruthenium(II) dichloride (Ru2(4)C13), synthesized as a racemic mixture was characterized by small-angle neutron scattering, light scattering, NMR, and electronic spectroscopies. The analysis of the SANS data indicates that micelles are prolate ellipsoids over the range of concentrations studied, with a relatively low aggregation number, and the micellization takes place gradually with increasing concentration. The presence of cyclodextrins (β-CD and γ-CD) induces the breakup of the micelles and helps to establish that micellization occurs at a very slow exchange rate compared to the NMR time scale. The open structure of this metallosurfactant enables the formation of very stable complexes of 3:1 stoichiometry, in which one CD threads one of the hydrocarbon tails and two CDs the other, in close contact with the polar head. The complex formed with β-CD, more stable than the one formed with the wider γ-CD, is capable of resolving the Δ and Λ enantiomers at high CD/surfactant molar ratios. The chiral recognition is possible due to the very specific interactions taking place when the β-CD covers-via its secondary rim-part of the diimine moiety connected to the hydrophobic tails. A SANS model comprising a binary mixture of hard spheres (complex + micelles) was successfully used to study quantitatively the effect of the CDs on the aggregation of the surfactant.

  8. About Maggie's Place.

    ERIC Educational Resources Information Center

    Emmens, Carol E.

    1982-01-01

    Describes "Maggie's Place," the library computer system of the Pikes Peak Library District, Colorado Springs, Colorado, noting its use as an electronic card catalog and community information file, accessibility by home users and library users, and terminal considerations. (EJS)

  9. Artist Place Settings

    ERIC Educational Resources Information Center

    Pellegrino, Linda

    2009-01-01

    Art history can be a little dry at times, but the author is always trying to incorporate new ways of teaching it. In this article, she describes a project in which students were to create a place setting out of clay that had to be unified through a famous artist's style. This place setting had to consist of at least five pieces (dinner plate, cup…

  10. Spatial mapping takes time.

    PubMed

    Whishaw, I Q

    1998-01-01

    The experiment tested the prediction that spatial mapping takes time and asked whether time use is reflected in the overt behavior of a performing animal. The study examines this question by exploiting the expected behavioral differences of control rats and rats with hippocampal formation damage induced with fimbria-fornix (FF) lesions on a spatial navigation task. Previous studies have shown that control rats use a mapping strategy, in which they use the relative positions of environmental cues to reach places in space, whereas FF rats use a cue-based strategy, in which they are guided by a single cue or their own body orientation. Therefore, control and FF rats were overtrained on a complex foraging task in which they left a burrow to retrieve eight food pellets hidden around the perimeter of a circular table. The control rats retrieved the food pellets in order of their distance from the burrow, took direct routes to the food, and made few errors, all of which suggested they used a spatial strategy. The FF rats were less likely to retrieve food as a function of its distance, took a circular path around the perimeter of the table, and made many errors, suggesting they used a cue-based strategy. Despite taking shorter routes than the FF rats, the control rats had proportionally slower response speeds. Their slow response speeds support the hypothesis that spatial mapping takes time and that mapping time is reflected in behavior. The results are discussed in relation to their relevance to spatial mapping theory, hippocampal function, and the evolution of foraging strategies.

  11. Diatom aggregation and dimethylsulfide production in phytoplankton blooms

    SciTech Connect

    Crocker, K.M.

    1994-01-01

    Phytoplankton blooms are crucial links in many of the earth's biogeochemical cycles. Blooms take up atmospheric carbon through photosynthesis, and sequester it on the ocean floor by sinking. Aggregation of single cells into [open quote]marine snow[close quote] particles speeds up the sinking of algal cells. Laboratory studies investigating the process of aggregation show that some species have a higher probability of aggregating than others, and that there exist several mechanisms for causing aggregation. Field studies confirm that some species are more likely to be found in aggregates than in the surrounding seawater. High latitude Premnesiophyte blooms are found to produce large amounts of dimethylsulflde (DMS), believed to be an important chemical in global thermoregulation. DMS is found to vary diurnally, possibly due to photooxidation by ultraviolet light. This possibility links the effects of DMS on cloud formation with the effects of increased ultraviolet light penetrating the earths ozone layer.

  12. pH-dependent aggregation of oligomeric Artocarpus hirsuta lectin on thermal denaturation.

    PubMed

    Gaikwad, Sushama M; Islam Khan, M

    2003-11-14

    The pH dependence of the activity, aggregation, and secondary structure of Artocarpus hirsuta lectin was studied using intrinsic and extrinsic fluorescence, light scattering, and circular dichroism. The lectin is more stable in the neutral and acidic than in the alkaline pH range, which is also reflected in the binding constants of the lectin to methyl alpha-galactopyranoside (me alpha-gal). The aggregation of the protein due to heat denaturation is prevented at both extremes of pH. The binding of hydrophobic dye to the lectin takes place at pH 1-2, which increases with increasing temperature. The exposure of hydrophobic patches at pH 1 is reversible. The secondary structure of the lectin is intact in the pH range of 1-8 and is distorted above pH 9. Aggregation of the protein due to heat denaturation is also prevented in the presence of guanidine hydrochloride (GdnHCl).

  13. 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

  14. 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.

  15. Optical properties of three-layer metal-organic nanoparticles with a molecular J-aggregate shell

    SciTech Connect

    Lebedev, V S; Medvedev, A S

    2013-11-30

    This paper examines the optical properties of two types of spherical three-component nanoparticles: (1) particles comprising a metallic core, outer organic dye J-aggregate shell and passive intermediate layer and (2) metallic nanoshells having an insulator or semiconductor core and coated with a molecular J-aggregate layer. The two types of nanoparticles are shown to differ significantly in the behaviour of electromagnetic fields and photoabsorption spectra. As a result of additional possibilities to control the magnitude and nature of the coupling between Frenkel excitons and localised surface plasmons in these systems, the spectral properties of the three-layer particles have radically new inherent features in comparison with earlier studied metal/J-aggregate bilayer particles. In the case of J-aggregate-coated metallic nanoshells, particular attention is paid to the strong plasmon – exciton coupling regime, which takes place when the plasmon resonance frequency of the nanoshell approaches the centre frequency of the J-band of the dye forming the outer layer of the particle. (optics of nanoparticles)

  16. Gateway to New Atlantis Attraction Takes Shape

    NASA Video Gallery

    The home of space shuttle Atlantis continues taking shape at the Kennedy Space Center Visitor Complex. Crews placed the nose cone atop the second of a replica pair of solid rocket boosters. A life-...

  17. Finding Place in Education

    ERIC Educational Resources Information Center

    Peters, Chris

    2011-01-01

    As a society, we are less and less comfortable in our localities. We have embraced the idea of a globalized placelessness, where everything, everywhere, resonates with a sameness. What do we lose, educationally and in society at large, when we reduce our inhabited places to those components that provide material wealth alone? If students and…

  18. Schools as Dangerous Places

    ERIC Educational Resources Information Center

    Potts, Anthony

    2006-01-01

    When students set off for school each day how many of them or their caregivers consider for a moment that they will spend the day at a potentially dangerous place? On the contrary, students and caregivers probably view schools as safe havens, and official research suggests that this is the case for the majority of teachers and pupils. However,…

  19. Tracking Self into Place

    ERIC Educational Resources Information Center

    Piersol, Laura

    2010-01-01

    In an effort to figure out what it means to educate "ecologically," I decided to track down some of the stories that I was living, telling and making as an educator. I ended up lost in the house of environmental education, stuck within the rooms of ecological science and political advocacy. Outside on the lawn sat the story of place based…

  20. Teaching With Historic Places.

    ERIC Educational Resources Information Center

    Greenberg, Ronald M., Ed.

    1993-01-01

    Designed for social studies educators, this theme issue presents 11 articles about historic places that feature a variety of ideas for elementary and secondary lesson plans, curricula, and program development. The articles are: (1) "Where did History Happen?" (Beth M. Boland); (2) "Creating a Partnership" (Carol D. Shull); (3) "Heritage Education:…

  1. The Value of Place

    ERIC Educational Resources Information Center

    Dentzau, Michael W.

    2014-01-01

    This commentary seeks to expand the dialogue on place-based science education presented in Katie Lynn Brkich's article, where the connections fifth grade students make between their formal earth science curriculum and their lived experiences are highlighted. The disconnect between the curriculum the students are offered and their immediate…

  2. Designing Places for Learning.

    ERIC Educational Resources Information Center

    Meek, Anne, Ed.

    This book presents information about the condition of schools around the United States. It also describes the link between architecture and academic success and offers suggestions for improving the design of existing and future school buildings. Eleven articles look at schools as places of deep meaning and show how that view can alter approaches…

  3. Creativity: Does Place Matter?

    ERIC Educational Resources Information Center

    Bradley, Finbarr

    2012-01-01

    This article argues that creativity has the greatest potential to flourish if a learning environment is embedded within a community that emphasises a deep sense of place. Yet in a globalised world, rootedness is often regarded as antithetical to creativity. But far from representing dead artefacts that are anti-modern and non-economic, culture and…

  4. Universities Are Funny Places!

    ERIC Educational Resources Information Center

    Lawless, Ann

    2006-01-01

    Universities are funny places. They have a strong sense of hierarchy and rank. They have an amazing disparity in salary levels and status between staff, are class conscious, and are run by a large bureaucracy that oils and keeps the machinery going. They operate as educational institutions and yet also are entrepreneurial, marketing themselves in…

  5. 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.

  6. Systematic Risk-Taking.

    ERIC Educational Resources Information Center

    Neihart, Maureen

    1999-01-01

    Describes systematic risk-taking, a strategy designed to develop skills and increase self-esteem, confidence, and courage in gifted youth. The steps of systematic risk-taking include understanding the benefits, initial self-assessment for risk-taking categories, identifying personal needs, determining a risk to take, taking the risk, and…

  7. Effect of additives on protein aggregation.

    PubMed

    Hamada, Hiroyuki; Arakawa, Tsutomu; Shiraki, Kentaro

    2009-06-01

    This paper overviews solution additives that affect protein stability and aggregation during refolding, heating, and freezing processes. Solution additives are mainly grouped into two classes, i.e., protein denaturants and stabilizers. The former includes guanidine, urea, strong ionic detergents, and certain chaotropic salts; the latter includes certain amino acids, sugars, polyhydric alcohols, osmolytes, and kosmotropic salts. However, there are solution additives that are not unambiguously placed into these two classes, including arginine, certain divalent cation salts (e.g., MgCl(2)) and certain polyhydric alcohols (e.g., ethylene glycol). Certain non-ionic or non-detergent surfactants, ionic liquids, amino acid derivatives, polyamines, and certain amphiphilic polymers may belong to this class. They have marginal effects on protein structure and stability, but are able to disrupt protein interactions. Information on additives that do not catalyze chemical reactions nor affect protein functions helps us to design protein solutions for increased stability or reduced aggregation. PMID:19519415

  8. Settings: In a Variety of Place. . .

    ERIC Educational Resources Information Center

    Cairo, Peter; And Others

    This document consists of the fourth section of a book of readings on issues related to adult career development. The four chapters in this fourth section focus on settings in which adult career development counseling may take place. "Career Planning and Development in Organizations" (Peter Cairo) discusses several concepts and definitions…

  9. The Right Place, The Right Time

    ERIC Educational Resources Information Center

    O'Callaghan, William G.; Irish, Charles M.

    2006-01-01

    Superintendents are in the right place at the right time to take advantage of a golden opportunity to reverse a trend that threatens the nation's schools and communities. They are now uniquely positioned to stop the retreat of good-hearted, well-intentioned citizens from public life. In this article, the authors present perpetual traps that…

  10. Kinetics of protein aggregation

    NASA Astrophysics Data System (ADS)

    Knowles, Tuomas

    2015-03-01

    Aggregation into linear nanostructures, notably amyloid and amyloid-like fibrils, is a common form of behaviour exhibited by a range of peptides and proteins. This process was initially discovered in the context of the aetiology of a range of neurodegenerative diseases, but has recently been recognised to of general significance and has been found at the origin of a number of beneficial functional roles in nature, including as catalytic scaffolds and functional components in biofilms. This talk discusses our ongoing efforts to study the kinetics of linear protein self-assembly by using master equation approaches combined with global analysis of experimental data.

  11. 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.

  12. Space Place Prime

    NASA Technical Reports Server (NTRS)

    Fitzpatrick, Austin J.; Novati, Alexander; Fisher, Diane K.; Leon, Nancy J.; Netting, Ruth

    2013-01-01

    Space Place Prime is public engagement and education software for use on iPad. It targets a multi-generational audience with news, images, videos, and educational articles from the Space Place Web site and other NASA sources. New content is downloaded daily (or whenever the user accesses the app) via the wireless connection. In addition to the Space Place Web site, several NASA RSS feeds are tapped to provide new content. Content is retained for the previous several days, or some number of editions of each feed. All content is controlled on the server side, so features about the latest news, or changes to any content, can be made without updating the app in the Apple Store. It gathers many popular NASA features into one app. The interface is a boundless, slidable- in-any-direction grid of images, unique for each feature, and iconized as image, video, or article. A tap opens the feature. An alternate list mode presents menus of images, videos, and articles separately. Favorites can be tagged for permanent archive. Face - book, Twitter, and e-mail connections make any feature shareable.

  13. Take Steps Toward a Healthier Life | Poster

    Cancer.gov

    The National Institutes of Health (NIH) is promoting wellness by encouraging individuals to take the stairs. In an effort to increase participation in this program, NIH has teamed up with Occupational Health Services (OHS). OHS is placing NIH-sponsored “Take the Stairs” stickers on stair entrances, stair exits, and elevators.

  14. 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.

  15. 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.

  16. The Take Action Project

    ERIC Educational Resources Information Center

    Boudreau, Sue

    2010-01-01

    The Take Action Project (TAP) was created to help middle school students take informed and effective action on science-related issues. The seven steps of TAP ask students to (1) choose a science-related problem of interest to them, (2) research their problem, (3) select an action to take on the problem, (4) plan that action, (5) take action, (6)…

  17. Influence of reactive gas admixture on transition metal cluster nucleation in a gas aggregation cluster source

    NASA Astrophysics Data System (ADS)

    Peter, Tilo; Polonskyi, Oleksandr; Gojdka, Björn; Mohammad Ahadi, Amir; Strunskus, Thomas; Zaporojtchenko, Vladimir; Biederman, Hynek; Faupel, Franz

    2012-12-01

    We quantitatively assessed the influence of reactive gases on the formation processes of transition metal clusters in a gas aggregation cluster source. A cluster source based on a 2 in. magnetron is used to study the production rate of titanium and cobalt clusters. Argon served as working gas for the DC magnetron discharge, and a small amount of reactive gas (oxygen and nitrogen) is added to promote reactive cluster formation. We found that the cluster production rate depends strongly on the reactive gas concentration for very small amounts of reactive gas (less than 0.1% of total working gas), and no cluster formation takes place in the absence of reactive species. The influence of discharge power, reactive gas concentration, and working gas pressure are investigated using a quartz micro balance in a time resolved manner. The strong influence of reactive gas is explained by a more efficient formation of nucleation seeds for metal-oxide or nitride than for pure metal.

  18. Histones Cause Aggregation and Fusion of Lipid Vesicles Containing Phosphatidylinositol-4-Phosphate

    PubMed Central

    Lete, Marta G.; Sot, Jesus; Gil, David; Valle, Mikel; Medina, Milagros; Goñi, Felix M.; Alonso, Alicia

    2015-01-01

    In a previous article, we demonstrated that histones (H1 or histone octamers) interact with negatively charged bilayers and induce extensive aggregation of vesicles containing phosphatidylinositol-4-phosphate (PIP) and, to a lesser extent, vesicles containing phosphatidylinositol (PI). Here, we found that vesicles containing PIP, but not those containing PI, can undergo fusion induced by histones. Fusion was demonstrated through the observation of intervesicular mixing of total lipids and inner monolayer lipids, and by ultrastructural and confocal microscopy studies. Moreover, in both PI- and PIP-containing vesicles, histones caused permeabilization and release of vesicular aqueous contents, but the leakage mechanism was different (all-or-none for PI and graded release for PIP vesicles). These results indicate that histones could play a role in the remodeling of the nuclear envelope that takes place during the mitotic cycle. PMID:25692591

  19. Male sleeping aggregation of multiple Eucerini bee genera (Hymenoptera: Apidae) in Chapada Diamantina, Bahia, Brazil

    PubMed Central

    Hipólito, Juliana; de Oliveira, Favízia F.

    2014-01-01

    Abstract Males of some groups of bees have to find a place outside the nests to sleep, sometimes forming “male sleeping aggregations”. Here we report the first record of “dense” male sleeping aggregation of two different genera of Eucerini bees observed in Bahia, Brazil. We discuss the possible aim of this kind of aggregation as well the plant utilized on aggregate. PMID:25349523

  20. Hydrophobically modified polyelectrolytes: Characterization, aggregation and adsorption

    NASA Astrophysics Data System (ADS)

    Islam, Mohammad Ferdous

    The focus of our work was to experimentally study the aggregation and adsorption behavior of model HM polyelectrolytes. Hydrophobically modified alkali soluble emulsions (HASE), the model HM polyelectrolytes, were chosen because they had complex architecture yet possessed key variables for systematic study. The HASE polymers have methacrylic acid (MAA) and ethyl acrylate (EA) in the backbone with pendent hydrophobic groups. Characterization of a single molecule is an important first step in understanding the aggregation and adsorption of these polymers. However, characterizations of the HASE polymers using conventional techniques such as gel permeation chromatography or static light scattering were difficult because of the hydrophobic association. In this study, two different approaches have been taken to prevent the hydrophobic association in aqueous solution: (1) hydrolyze the polymer to cleave the hydrophobic constituents, and (2) use methyl beta-cyclodextrin that has a hydrophobic cavity and a hydrophilic outer shell, to shield the hydrophobes from associating. By taking these two approaches and using gel permeation chromatography (GPC), dynamic (DLS) and static (SLS) light scattering techniques, the molecular weight, hydrodynamic radius and radius of gyration of a single molecule were determined. Except for one chemical site, we were able to determine that branching or grafting did not occur in the polymer chain during synthesis. Our aggregation studies showed that, in aqueous solutions, the HASE polymers formed small aggregates (presumably single micelles of single or a few chains) and large aggregates (presumably formed by bridging between micelles). The radii and masses of the larger aggregates, measured using DLS and SLS, were found to increase with an increase in the polymer concentration, indicating an open association process for the HASE polymers. Our SLS results also showed that, at high salt concentration, the aggregates of the HASE polymer with

  1. Role of clay minerals in the formation of atmospheric aggregates of Saharan dust

    NASA Astrophysics Data System (ADS)

    Cuadros, Javier; Diaz-Hernandez, José L.; Sanchez-Navas, Antonio; Garcia-Casco, Antonio

    2015-11-01

    Saharan dust can travel long distances in different directions across the Atlantic and Europe, sometimes in episodes of high dust concentration. In recent years it has been discovered that Saharan dust aerosols can aggregate into large, approximately spherical particles of up to 100 μm generated within raindrops that then evaporate, so that the aggregate deposition takes place most times in dry conditions. These aerosol aggregates are an interesting phenomenon resulting from the interaction of mineral aerosols and atmospheric conditions. They have been termed "iberulites" due to their discovery and description from aerosol deposits in the Iberian Peninsula. Here, these aggregates are further investigated, in particular the role of the clay minerals in the aggregation process of aerosol particles. Iberulites, and common aerosol particles for reference, were studied from the following periods or single dust events and locations: June 1998 in Tenerife, Canary Islands; June 2001 to August 2002, Granada, Spain; 13-20 August 2012, Granada; and 1-6 June 2014, Granada. Their mineralogy, chemistry and texture were analysed using X-ray diffraction, electron microprobe analysis, SEM and TEM. The mineral composition and structure of the iberulites consists of quartz, carbonate and feldspar grains surrounded by a matrix of clay minerals (illite, smectite and kaolinite) that also surrounds the entire aggregate. Minor phases, also distributed homogenously within the iberulites, are sulfates and Fe oxides. Clays are apparently more abundant in the iberulites than in the total aerosol deposit, suggesting that iberulite formation concentrates clays. Details of the structure and composition of iberulites differ from descriptions of previous samples, which indicates dependence on dust sources and atmospheric conditions, possibly including anthropic activity. Iberulites are formed by coalescence of aerosol mineral particles captured by precursor water droplets. The concentration of

  2. 12 CFR 621.7 - Rule of aggregation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Performance and Valuation Assessment § 621.7 Rule of aggregation. (a) When one loan to a borrower is placed in... related borrower are so financially interdependent with the borrower's operations that the economic survival of one will materially affect the economic survival of the other, determined in accordance...

  3. In-place HEPA filter penetration test

    SciTech Connect

    Bergman, W.; Wilson, kK.; Elliott, J.; Bettencourt, B.; Slawski, J.W.

    1997-01-01

    We have demonstrated the feasibility of conducting penetration tests on high efficiency particulate air (HEPA) filters as installed in nuclear ventilation systems. The in-place penetration test, which is designed to yield equivalent penetration measurements as the standard DOP efficiency test, is based on measuring the aerosol penetration of the filter installation as a function of particle size using a portable laser particle counter. This in-place penetration test is compared to the current in-place leak test using light scattering photometers for single HEPA filter installations and for HEPA filter plenums using the shroud method. Test results show the in-place penetration test is more sensitive than the in-place leak test, has a similar operating procedure, but takes longer to conduct. Additional tests are required to confirm that the in-place penetration test yields identical results as the standard dioctyl phthalate (DOP) penetration test for HEPA filters with controlled leaks in the filter and gasket and duct by-pass leaks. Further development of the procedure is also required to reduce the test time before the in- place penetration test is practical.

  4. In-place HEPA filter penetration test

    SciTech Connect

    Bergman, W.; Wilson, K.; Elliott, J.

    1997-08-01

    We have demonstrated the feasibility of conducting penetration tests on high efficiency particulate air (HEPA) filters as installed in nuclear ventilation systems. The in-place penetration test, which is designed to yield equivalent penetration measurements as the standard DOP efficiency test, is based on measuring the aerosol penetration of the filter installation as a function of particle size using a portable laser particle counter. This in-place penetration test is compared to the current in-place leak test using light scattering photometers for single HEPA filter installations and for HEPA filter plenums using the shroud method. Test results show the in-place penetration test is more sensitive than the in-place leak test, has a similar operating procedure, but takes longer to conduct. Additional tests are required to confirm that the in-place penetration test yields identical results as the standard dioctyl phthalate (DOP) penetration test for HEPA filters with controlled leaks in the filter and gasket and duct by-pass leaks. Further development of the procedure is also required to reduce the test time before the in-place penetration test is practical. 14 refs., 14 figs., 3 tabs.

  5. Breastfeeding in public places.

    PubMed

    McIntyre, E; Turnbull, D; Hiller, J E

    1999-06-01

    This study reports the results of a survey of restaurant and shopping center managers concerning breastfeeding in their facilities. Managers from 66 restaurants and 27 shopping centers were interviewed by telephone. One-third of the restaurant managers and 48% of the shopping center managers stated that a mother could breastfeed anywhere in their facility regardless of what other customers might say. The remaining managers would either discourage breastfeeding anywhere in their facility, suggest a mother move to a more secluded area if she wished to breastfeed, or were unsure how they would react. The variability in support for breastfeeding by managers of restaurants and shopping centers will continue to create uncertainty for mothers wishing to breastfeed in these public places.

  6. Place memory in crickets

    PubMed Central

    Wessnitzer, Jan; Mangan, Michael; Webb, Barbara

    2008-01-01

    Certain insect species are known to relocate nest or food sites using landmarks, but the generality of this capability among insects, and whether insect place memory can be used in novel task settings, is not known. We tested the ability of crickets to use surrounding visual cues to relocate an invisible target in an analogue of the Morris water maze, a standard paradigm for spatial memory tests on rodents. Adult female Gryllus bimaculatus were released into an arena with a floor heated to an aversive temperature, with one hidden cool spot. Over 10 trials, the time taken to find the cool spot decreased significantly. The best performance was obtained when a natural scene was provided on the arena walls. Animals can relocate the position from novel starting points. When the scene is rotated, they preferentially approach the fictive target position corresponding to the rotation. We note that this navigational capability does not necessarily imply the animal has an internal spatial representation. PMID:18230590

  7. STAND: Surface Tension for Aggregation Number Determination.

    PubMed

    Garrido, Pablo F; Brocos, Pilar; Amigo, Alfredo; García-Río, Luis; Gracia-Fadrique, Jesús; Piñeiro, Ángel

    2016-04-26

    Taking advantage of the extremely high dependence of surface tension on the concentration of amphiphilic molecules in aqueous solution, a new model based on the double equilibrium between free and aggregated molecules in the liquid phase and between free molecules in the liquid phase and those adsorbed at the air/liquid interface is presented and validated using literature data and fluorescence measurements. A key point of the model is the use of both the Langmuir isotherm and the Gibbs adsorption equation in terms of free molecules instead of the nominal concentration of the solute. The application of the model should be limited to non ionic compounds since it does not consider the presence of counterions. It requires several coupled nonlinear fittings for which we developed a software that is publicly available in our server as a web application. Using this tool, it is straightforward to get the average aggregation number of an amphiphile, the micellization free energy, the adsorption constant, the maximum surface excess (and so the minimum area per molecule), the distribution of solute in the liquid phase between free and aggregate species, and the surface coverage in only a couple of seconds, just by uploading a text file with surface tension vs concentration data and the corresponding uncertainties. PMID:27048988

  8. Platelet aggregation associated with ethanol intoxication

    SciTech Connect

    Volk, S.; Walenga, J.; Fareed, J.; Schumacher, H. )

    1989-02-09

    Alcohol is known to produce profound effects on blood; during chronic intoxication, prolongation of bleeding time has been reported. Utilizing human platelet rich plasma, we have studied the effect of alcohol on epinephrine, arachidonic acid and ADP induced aggregation. Control responses were obtained with saline from which the relative inhibition by alcohol was calculated. These studies were carried out at a concentration of 1.25-5.0 mg/ml which represents 0.125-0.5% alcohol blood levels. From 25 normal male and female volunteers, without prior hemostatic defects or drug ingestion, a dose-dependent inhibition by alcohol of all three agonist induced aggregations was noted. Alcohol itself did not produce any aggregation response. These studies demonstrate that alcohol at levels which are reached during intoxication is capable of impairing platelet function. The implication of this finding on the bleeding complications in healthy intoxicated patients may be significant during traumatic events, and individuals taking antiplatelet drugs may present a more serious hemostatic deficit during alcohol intoxication.

  9. Elucidation of flow-mediated tumour cell-induced platelet aggregation using an ultrasound standing wave trap

    PubMed Central

    Bazou, D; Santos-Martinez, MJ; Medina, C; Radomski, MW

    2011-01-01

    BACKGROUND AND PURPOSE Tumour cells activate and aggregate platelets [tumour cell-induced platelet aggregation (TCIPA)] and this process plays an important role in the successful metastasis of cancer cells. To date, most studies on TCIPA have been conducted under no-flow conditions. In this study, we have investigated TCIPA in real time under flow conditions, using an ultrasound standing wave trap that allows formation and levitation of cancer cell clusters in suspension, thus mimicking the conditions generated by flowing blood. EXPERIMENTAL APPROACH Using 59M adenocarcinoma and HT1080 fibrosarcoma cells and human platelets, cancer cell cluster–platelet aggregates were imaged in real time using epi-fluorescence microscopy (F-actin) and investigated in detail using confocal microscopy (matrix metalloproteinase-2-GPIIb/IIIa co-localization) and scanning electron and helium-ion microscopy (<1 nm resolution). The release of gelatinases from aggregates was studied using zymography. KEY RESULTS We found that platelet activation and aggregation takes place on the surface of cancer cells (TCIPA), leading to time-dependent disruption of cancer cell clusters. Pharmacological modulation of TCIPA revealed that EDTA, prostacyclin, o-phenanthroline and apyrase significantly down-regulated TCIPA and, in turn, delayed cell cluster disruption, However, EGTA and aspirin were ineffective. Pharmacological inhibition of TCIPA correlated with the down-regulation of platelet activation as shown by flow-cytometry assay of platelet P-selectin. CONCLUSION AND IMPLICATIONS Our results show for the first time, that during TCIPA, platelet activation disrupts cancer cell clusters and this can contribute to metastasis. Thus, selective targeting of platelet aggregate–cancer cell clusters may be an important strategy to control metastasis. PMID:21182493

  10. 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

  11. 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…

  12. 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.

  13. Characteristics of aggregation of daily rainfall in a middle-latitudes region during a climate variability in annual rainfall amount

    NASA Astrophysics Data System (ADS)

    Lucero, Omar A.; Rozas, Daniel

    Climate variability in annual rainfall occurs because the aggregation of daily rainfall changes. A topic open to debate is whether that change takes place because rainfall becomes more intense, or because it rains more often, or a combination of both. The answer to this question is of interest for water resources planning, hydrometeorological design, and agricultural management. Change in the number of rainy days can cause major disruptions in hydrological and ecological systems, with important economic and social effects. Furthermore, the characteristics of daily rainfall aggregation in ongoing climate variability provide a reference to evaluate the capability of GCM to simulate changes in the hydrologic cycle. In this research, we analyze changes in the aggregation of daily rainfall producing a climate positive trend in annual rainfall in central Argentina, in the southern middle-latitudes. This state-of-the-art agricultural region has a semiarid climate with dry and wet seasons. Weather effects in the region influence world-market prices of several crops. Results indicate that the strong positive trend in seasonal and annual rainfall amount is produced by an increase in number of rainy days. This increase takes place in the 3-month periods January-March (summer) and April-June (autumn). These are also the 3-month periods showing a positive trend in the mean of annual rainfall. The mean of the distribution of annual number of rainy day (ANRD) increased in 50% in a 36-year span (starting at 44 days/year). No statistically significant indications on time changes in the probability distribution of daily rainfall amount were found. Non-periodic fluctuations in the time series of annual rainfall were analyzed using an integral wavelet transform. Fluctuations with a time scale of about 10 and 20 years construct the trend in annual rainfall amount. These types of non-periodic fluctuations have been observed in other regions of the world. This suggests that results of

  14. Utilization of sewage sludge in the manufacture of lightweight aggregate.

    PubMed

    Franus, Małgorzata; Barnat-Hunek, Danuta; Wdowin, Magdalena

    2016-01-01

    This paper presents a comprehensive study on the possibility of sewage sludge management in a sintered ceramic material such as a lightweight aggregate. Made from clay and sludge lightweight aggregates were sintered at two temperatures: 1100 °C (name of sample LWA1) and 1150 °C (name of sample LWA2). Physical and mechanical properties indicate that the resulting expanded clay aggregate containing sludge meets the basic requirements for lightweight aggregates. The presence of sludge supports the swelling of the raw material, thereby causing an increase in the porosity of aggregates. The LWA2 has a lower value of bulk particle density (0.414 g/cm(3)), apparent particle density (0.87 g/cm(3)), and dry particle density (2.59 g/cm(3)) than it is in the case of LWA1 where these parameters were as follows: bulk particle density 0.685 g/cm(3), apparent particle density 1.05 g/cm(3), and dry particle density 2.69 g/cm(3). Water absorption and porosity of LWA1 (WA = 14.4 %, P = 60 %) are lower than the LWA2 (WA = 16.2 % and P = 66 %). This is due to the higher heating temperature of granules which make the waste gases, liberating them from the decomposition of organic sewage sludge. The compressive strength of LWA2 aggregate is 4.64 MPa and for LWA1 is 0.79 MPa. Results of leaching tests of heavy metals from examined aggregates have shown that insoluble metal compounds are placed in silicate and aluminosilicate structure of the starting materials (clays and sludges), whereas soluble substances formed crystalline skeleton of the aggregates. The thermal synthesis of lightweight aggregates from clay and sludge mixture is a waste-free method of their development. PMID:26635022

  15. Utilization of sewage sludge in the manufacture of lightweight aggregate.

    PubMed

    Franus, Małgorzata; Barnat-Hunek, Danuta; Wdowin, Magdalena

    2016-01-01

    This paper presents a comprehensive study on the possibility of sewage sludge management in a sintered ceramic material such as a lightweight aggregate. Made from clay and sludge lightweight aggregates were sintered at two temperatures: 1100 °C (name of sample LWA1) and 1150 °C (name of sample LWA2). Physical and mechanical properties indicate that the resulting expanded clay aggregate containing sludge meets the basic requirements for lightweight aggregates. The presence of sludge supports the swelling of the raw material, thereby causing an increase in the porosity of aggregates. The LWA2 has a lower value of bulk particle density (0.414 g/cm(3)), apparent particle density (0.87 g/cm(3)), and dry particle density (2.59 g/cm(3)) than it is in the case of LWA1 where these parameters were as follows: bulk particle density 0.685 g/cm(3), apparent particle density 1.05 g/cm(3), and dry particle density 2.69 g/cm(3). Water absorption and porosity of LWA1 (WA = 14.4 %, P = 60 %) are lower than the LWA2 (WA = 16.2 % and P = 66 %). This is due to the higher heating temperature of granules which make the waste gases, liberating them from the decomposition of organic sewage sludge. The compressive strength of LWA2 aggregate is 4.64 MPa and for LWA1 is 0.79 MPa. Results of leaching tests of heavy metals from examined aggregates have shown that insoluble metal compounds are placed in silicate and aluminosilicate structure of the starting materials (clays and sludges), whereas soluble substances formed crystalline skeleton of the aggregates. The thermal synthesis of lightweight aggregates from clay and sludge mixture is a waste-free method of their development.

  16. 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

  17. 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.

  18. Nanoparticle aggregation: principles and modeling.

    PubMed

    Zhang, Wen

    2014-01-01

    The high surface area to volume ratio of nanoparticles usually results in highly reactive and colloidal instability compared to their bulk counterparts. Aggregation as well as many other transformations (e.g., dissolution) in the environment may alter the physiochemical properties, reactivity, fate, transport, and biological interactions (e.g., bioavailability and uptake) of nanoparticles. The unique properties pertinent to nanoparticles, such as shape, size, surface characteristics, composition, and electronic structures, greatly challenge the ability of colloid science to understand nanoparticle aggregation and its environmental impacts. This review briefly introduces fundamentals about aggregation, fractal dimensions, classic and extended Derjaguin-Landau-Verwey-Overbeak (DLVO) theories, aggregation kinetic modeling, experimental measurements, followed by detailed discussions on the major factors on aggregation and subsequent effects on nanomaterial transport and reactivity.

  19. 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

  20. 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.

  1. 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

  2. Aggregated Indexing of Biomedical Time Series Data

    PubMed Central

    Woodbridge, Jonathan; Mortazavi, Bobak; Sarrafzadeh, Majid; Bui, Alex A.T.

    2016-01-01

    Remote and wearable medical sensing has the potential to create very large and high dimensional datasets. Medical time series databases must be able to efficiently store, index, and mine these datasets to enable medical professionals to effectively analyze data collected from their patients. Conventional high dimensional indexing methods are a two stage process. First, a superset of the true matches is efficiently extracted from the database. Second, supersets are pruned by comparing each of their objects to the query object and rejecting any objects falling outside a predetermined radius. This pruning stage heavily dominates the computational complexity of most conventional search algorithms. Therefore, indexing algorithms can be significantly improved by reducing the amount of pruning. This paper presents an online algorithm to aggregate biomedical times series data to significantly reduce the search space (index size) without compromising the quality of search results. This algorithm is built on the observation that biomedical time series signals are composed of cyclical and often similar patterns. This algorithm takes in a stream of segments and groups them to highly concentrated collections. Locality Sensitive Hashing (LSH) is used to reduce the overall complexity of the algorithm, allowing it to run online. The output of this aggregation is used to populate an index. The proposed algorithm yields logarithmic growth of the index (with respect to the total number of objects) while keeping sensitivity and specificity simultaneously above 98%. Both memory and runtime complexities of time series search are improved when using aggregated indexes. In addition, data mining tasks, such as clustering, exhibit runtimes that are orders of magnitudes faster when run on aggregated indexes.

  3. Teaching Keynes's Principle of Effective Demand Using the Aggregate Labor Market Diagram.

    ERIC Educational Resources Information Center

    Dalziel, Paul; Lavoie, Marc

    2003-01-01

    Suggests a method to teach John Keynes's principle of effective demand using a standard aggregate labor market diagram familiar to students taking advanced undergraduate macroeconomics courses. States the analysis incorporates Michal Kalecki's version to show Keynesian unemployment as a point on the aggregate labor demand curve inside the…

  4. Rover Takes a Sunday Drive

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This animation, made with images from the Mars Exploration Rover Spirit hazard-identification camera, shows the rover's perspective of its first post-egress drive on Mars Sunday. Engineers drove Spirit approximately 3 meters (10 feet) toward its first rock target, a football-sized, mountain-shaped rock called Adirondack. The drive took approximately 30 minutes to complete, including time stopped to take images. Spirit first made a series of arcing turns totaling approximately 1 meter (3 feet). It then turned in place and made a series of short, straightforward movements totaling approximately 2 meters (6.5 feet).

  5. The Greenhouse: A Place for Year-Round Plant Investigations.

    ERIC Educational Resources Information Center

    Hanif, Muhammad

    1989-01-01

    Activities that may take place in a greenhouse are discussed. Included are learning how to grow plants, plant growth, soil, vegetative reproduction, and plant habitat adaptations. Materials, procedures, and results are presented for the activities. (CW)

  6. Aggregation Properties of the Chromonic Liquid Crystal Benzopurpurin 4B

    NASA Astrophysics Data System (ADS)

    McKitterick, Christopher; Collings, Peter

    2009-03-01

    Benzopurpurin 4B (BPP) is a textile dye very similar to the common indicator Congo Red. As is true for all chromonics, the absorption spectrum is concentration dependent at low concentrations. If this dependence is used to estimate a free energy change for aggregation, it is higher than has been determined for other systems. Unlike other recently investigated chromonic liquid crystals, BPP forms a liquid crystal phase at extremely low concentrations, about 0.5 wt%. Also unlike these other chromonic liquid crystals, the aggregation kinetics are exceedingly slow. X-ray diffraction and light scattering measurements indicate that the aggregates of BPP are much larger than for chromonic systems that form liquid crystals at higher concentrations. BPP aggregates can be imaged using confocal microscopy, revealing a length distribution centered at 3 μm for a solution forced through a 0.2 μm filter. Over days the aggregates lengthen to well over 10 μm. The diameter of the aggregate images is slightly greater than the diffraction limit of the microscope, placing an upper limit on the diameter of 0.14 μm. These dimensions are consistent with the light scattering results.

  7. Embryo Aggregation in Pig Improves Cloning Efficiency and Embryo Quality.

    PubMed

    Buemo, Carla Paola; Gambini, Andrés; Moro, Lucia Natalia; Hiriart, María Inés; Fernández-Martín, Rafael; Collas, Philippe; Salamone, Daniel Felipe

    2016-01-01

    In this study, we analyzed the effects of the cloned embryo aggregation on in vitro embryo development and embryo quality by measuring blastocyst diameter and cell number, DNA fragmentation levels and the expression of genes associated with pluripotency, apoptosis, trophoblast and DNA methylation in the porcine. Zona-free reconstructed cloned embryos were cultured in the well of the well system, placing one (1x non aggregated group) or three (3x group) embryos per microwell. Our results showed that aggregation of three embryos increased blastocyst formation rate and blastocyst diameter of cloned pig embryos. DNA fragmentation levels in 3x aggregated cloned blastocysts were significantly decreased compared to 1x blastocysts. Levels of Oct4, Klf4, Igf2, Bax and Dnmt 1 transcripts were significantly higher in aggregated embryos, whereas Nanog levels were not affected. Transcripts of Cdx2 and Bcl-xl were essentially non-detectable. Our study suggests that embryo aggregation in the porcine may be beneficial for cloned embryo development and embryo quality, through a reduction in apoptotic levels and an improvement in cell reprogramming.

  8. Embryo Aggregation in Pig Improves Cloning Efficiency and Embryo Quality

    PubMed Central

    Buemo, Carla Paola; Gambini, Andrés; Moro, Lucia Natalia; Hiriart, María Inés; Fernández-Martín, Rafael; Collas, Philippe; Salamone, Daniel Felipe

    2016-01-01

    In this study, we analyzed the effects of the cloned embryo aggregation on in vitro embryo development and embryo quality by measuring blastocyst diameter and cell number, DNA fragmentation levels and the expression of genes associated with pluripotency, apoptosis, trophoblast and DNA methylation in the porcine. Zona-free reconstructed cloned embryos were cultured in the well of the well system, placing one (1x non aggregated group) or three (3x group) embryos per microwell. Our results showed that aggregation of three embryos increased blastocyst formation rate and blastocyst diameter of cloned pig embryos. DNA fragmentation levels in 3x aggregated cloned blastocysts were significantly decreased compared to 1x blastocysts. Levels of Oct4, Klf4, Igf2, Bax and Dnmt 1 transcripts were significantly higher in aggregated embryos, whereas Nanog levels were not affected. Transcripts of Cdx2 and Bcl-xl were essentially non-detectable. Our study suggests that embryo aggregation in the porcine may be beneficial for cloned embryo development and embryo quality, through a reduction in apoptotic levels and an improvement in cell reprogramming. PMID:26894831

  9. Embryo Aggregation in Pig Improves Cloning Efficiency and Embryo Quality.

    PubMed

    Buemo, Carla Paola; Gambini, Andrés; Moro, Lucia Natalia; Hiriart, María Inés; Fernández-Martín, Rafael; Collas, Philippe; Salamone, Daniel Felipe

    2016-01-01

    In this study, we analyzed the effects of the cloned embryo aggregation on in vitro embryo development and embryo quality by measuring blastocyst diameter and cell number, DNA fragmentation levels and the expression of genes associated with pluripotency, apoptosis, trophoblast and DNA methylation in the porcine. Zona-free reconstructed cloned embryos were cultured in the well of the well system, placing one (1x non aggregated group) or three (3x group) embryos per microwell. Our results showed that aggregation of three embryos increased blastocyst formation rate and blastocyst diameter of cloned pig embryos. DNA fragmentation levels in 3x aggregated cloned blastocysts were significantly decreased compared to 1x blastocysts. Levels of Oct4, Klf4, Igf2, Bax and Dnmt 1 transcripts were significantly higher in aggregated embryos, whereas Nanog levels were not affected. Transcripts of Cdx2 and Bcl-xl were essentially non-detectable. Our study suggests that embryo aggregation in the porcine may be beneficial for cloned embryo development and embryo quality, through a reduction in apoptotic levels and an improvement in cell reprogramming. PMID:26894831

  10. Fractal aggregates in Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Cabane, M.; Rannou, P.; Chassefiere, E.; Israel, G.

    1993-04-01

    The cluster structure of Titan's atmosphere was modeled by using an Eulerian microphysical model with the specific formulation of microphysical laws applying to fractal particles. The growth of aggregates in the settling phase was treated by introducing the fractal dimension as a parameter of the model. The model was used to obtain a vertical distribution of size and number density of the aggregates for different production altitudes. Results confirm previous estimates of the formation altitude of photochemical aerosols. The vertical profile of the effective radius of aggregates was calculated as a function of the visible optical depth.

  11. Active motion, communicative aggregations, and the spatial closure of Umwelt.

    PubMed

    Kull, K

    2000-01-01

    On the basis of a simple model of movable organisms that are supplied by semiotic force of attraction or repulsion, several general features of spatial behavior are demonstrated: (1) the stochastic spatial distribution of actively moving organisms is unstable; (2) simple or complex aggregations of organisms appear as a result of active motion; and (3) the ability for active motion ties the organisms with place. These results show that models that apply an internalist approach can considerably simplify the theory of spatial behavior of organic systems. Explanations based on the effects of Darwinian fitness may not be necessary for understanding the origin of biological aggregations.

  12. Binding of Folic Acid Induces Specific Self-Aggregation of Lactoferrin: Thermodynamic Characterization.

    PubMed

    Tavares, Guilherme M; Croguennec, Thomas; Lê, Sébastien; Lerideau, Olivia; Hamon, Pascaline; Carvalho, Antônio F; Bouhallab, Saïd

    2015-11-17

    In the study presented here, we investigated the interaction at pH 5.5 between folic acid (FA) and lactoferrin (LF), a positively charged protein. We found a binding constant Ka of 10(5) M(-1) and a high stoichiometry of 10 mol of FA/mol of LF. The size and charge of the complexes formed evolved during titration experiments. Increasing the ionic strength to 50 mM completely abolished the isothermal titration calorimetry (ITC) signal, suggesting the predominance of electrostatic interactions in the exothermic binding obtained. We developed a theoretical model that explains the complex triphasic ITC profile. Our results revealed a two-step mechanism: FA/LF interaction followed by self-association of the complexes thus formed. We suggest that 10 FA molecules bind to LF to form saturated reactive complexes (FA10/LF) that further self-associate into aggregates with a finite size of around 15 nm. There is thus a critical saturation degree of the protein, above which the self-association can take place. We present here the first results that provide comprehensive details of the thermodynamics of FA/LF complexation-association. Given the high stoichiometry, allowing a load of 55 mg of FA/g of LF, we suggest that FA/LF aggregates would be an effective vehicle for FA in fortified drinks. PMID:26488446

  13. Ice-induced partial unfolding and aggregation of an integral membrane protein.

    PubMed

    Garber Cohen, Iona P; Castello, Pablo R; González Flecha, F Luis

    2010-11-01

    Although the deleterious effects of ice on water-soluble proteins are well established, little is known about the freeze stability of membrane proteins. Here we explore this issue through a combined kinetic and spectroscopic approach using micellar-purified plasma membrane calcium pump as a model. The ATPase activity of this protein significantly diminished after freezing using a slow-cooling procedure, with the decrease in the activity being an exponential function of the storage time at 253K, with t(½)=3.9±0.6h. On the contrary, no significant changes on enzyme activity were detected when a fast cooling procedure was performed. Regardless of the cooling rate, successive freeze-thaw cycles produced an exponential decrease in the Ca(2+)-ATPase activity, with the number of cycles at which the activity was reduced to half being 9.2±0.3 (fast cooling) and 3.7±0.2 (slow cooling). PAGE analysis showed that neither degradation nor formation of SDS-stable aggregates of the protein takes place during protein inactivation. Instead, the inactivation process was found to be associated with the irreversible partial unfolding of the polypeptide chain, as assessed by Trp fluorescence, far UV circular dichroism, and 1-anilino-naphtalene-8-sulfonate binding. This inactive protein undergoes, in a later stage, a further irreversible transformation leading to large aggregates.

  14. Taking centre stage...

    NASA Astrophysics Data System (ADS)

    1998-11-01

    HAMLET (Highly Automated Multimedia Light Enhanced Theatre) was the star performance at the recent finals of the `Young Engineer for Britain' competition, held at the Commonwealth Institute in London. This state-of-the-art computer-controlled theatre lighting system won the title `Young Engineers for Britain 1998' for David Kelnar, Jonathan Scott, Ramsay Waller and John Wyllie (all aged 16) from Merchiston Castle School, Edinburgh. HAMLET replaces conventional manually-operated controls with a special computer program, and should find use in the thousands of small theatres, schools and amateur drama productions that operate with limited resources and without specialist expertise. The four students received a £2500 prize between them, along with £2500 for their school, and in addition they were invited to spend a special day with the Royal Engineers. A project designed to improve car locking systems enabled Ian Robinson of Durham University to take the `Working in industry award' worth £1000. He was also given the opportunity of a day at sea with the Royal Navy. Other prizewinners with their projects included: Jun Baba of Bloxham School, Banbury (a cardboard armchair which converts into a desk and chair); Kobika Sritharan and Gemma Hancock, Bancroft's School, Essex (a rain warning system for a washing line); and Alistair Clarke, Sam James and Ruth Jenkins, Bishop of Llandaff High School, Cardiff (a mechanism to open and close the retractable roof of the Millennium Stadium in Cardiff). The two principal national sponsors of the competition, which is organized by the Engineering Council, are Lloyd's Register and GEC. Industrial companies, professional engineering institutions and educational bodies also provided national and regional prizes and support. During this year's finals, various additional activities took place, allowing the students to surf the Internet and navigate individual engineering websites on a network of computers. They also visited the

  15. Surface fractals in liposome aggregation.

    PubMed

    Roldán-Vargas, Sándalo; Barnadas-Rodríguez, Ramon; Quesada-Pérez, Manuel; Estelrich, Joan; Callejas-Fernández, José

    2009-01-01

    In this work, the aggregation of charged liposomes induced by magnesium is investigated. Static and dynamic light scattering, Fourier-transform infrared spectroscopy, and cryotransmission electron microscopy are used as experimental techniques. In particular, multiple intracluster scattering is reduced to a negligible amount using a cross-correlation light scattering scheme. The analysis of the cluster structure, probed by means of static light scattering, reveals an evolution from surface fractals to mass fractals with increasing magnesium concentration. Cryotransmission electron microscopy micrographs of the aggregates are consistent with this interpretation. In addition, a comparative analysis of these results with those previously reported in the presence of calcium suggests that the different hydration energy between lipid vesicles when these divalent cations are present plays a fundamental role in the cluster morphology. This suggestion is also supported by infrared spectroscopy data. The kinetics of the aggregation processes is also analyzed through the time evolution of the mean diffusion coefficient of the aggregates. PMID:19257067

  16. Surface fractals in liposome aggregation.

    PubMed

    Roldán-Vargas, Sándalo; Barnadas-Rodríguez, Ramon; Quesada-Pérez, Manuel; Estelrich, Joan; Callejas-Fernández, José

    2009-01-01

    In this work, the aggregation of charged liposomes induced by magnesium is investigated. Static and dynamic light scattering, Fourier-transform infrared spectroscopy, and cryotransmission electron microscopy are used as experimental techniques. In particular, multiple intracluster scattering is reduced to a negligible amount using a cross-correlation light scattering scheme. The analysis of the cluster structure, probed by means of static light scattering, reveals an evolution from surface fractals to mass fractals with increasing magnesium concentration. Cryotransmission electron microscopy micrographs of the aggregates are consistent with this interpretation. In addition, a comparative analysis of these results with those previously reported in the presence of calcium suggests that the different hydration energy between lipid vesicles when these divalent cations are present plays a fundamental role in the cluster morphology. This suggestion is also supported by infrared spectroscopy data. The kinetics of the aggregation processes is also analyzed through the time evolution of the mean diffusion coefficient of the aggregates.

  17. Electromagnetic charges in aggregation phenomena.

    NASA Astrophysics Data System (ADS)

    Rioux, Claude; Slobodrian, R. J.

    Introduction The mechanism of fine particles aggregation is of great importance in many areas of research, in particular environment sciences where the state of aggregation defines the removal speed of dust from the atmosphere. The study of this mechanism is also important to understand the first stage of planet formation from the solar nebula. The aggregates formed are generally fractals and, as mentioned in the literature [1], the fractal dimensions and the site growth probability measures of the resulting fractal structures strongly depend on the properties of the forces that cause the aggregation. Theory and experimental apparatus We began this study by the aggregation between two charged particles and we are now consid-ering the aggregation between two magnetized particles. The aggregations are produced in a gas at a pressure between 10 and 1000 mbar and by using the applicable simplifications; we find that the distance (r) between the particles as a function of time (t) is given by the following equations: r=Ce(tf -t)1/3 for the electrical attraction r=Cm(tf -t)1/5 for the magnetic dipoles aligned in an external magnetic field. The apparatus built for these measurements consists of an experimental cell from which two perpendicular views are combined via an optical system in one image recorded by a video camera. From the video, we can then measure the distance between the particles as a function of time and reconstruct the trajectories in 3-D. The horizontal and vertical resolutions are respectively 0.86 and 0.92 microns per pixel. With a depth of field of 250 microns, the usable volume for 3-D observation in then 250 microns x 250 microns x 443 microns. Results and discussion A first version of the apparatus was tested on an electrical force aggregation and the results [2] show that the corresponding equation is a good representation of the phenomenon. Preliminary results, from an experiment using iron particles, show that the magnetic force can be seen in

  18. 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

  19. Creating Sacred Places for Students in Grades 9-12.

    ERIC Educational Resources Information Center

    Fox, Sandra J.

    This guide attempts to help teachers of American Indian students in grades 9-12 provide a culturally relevant education that takes place in the regular classroom, includes content related to Indian students' lives, makes students proud, expands to other experiences, and enhances learning. Creating sacred places means responding appropriately to…

  20. Creating Sacred Places for Students in Grades 7&8.

    ERIC Educational Resources Information Center

    Fox, Sandra J.

    This guide attempts to help teachers of American Indian students in grades 7-8 provide a culturally relevant education that takes place in the regular classroom, includes content related to Indian students' lives, makes students proud, expands to other experiences, and enhances learning. Creating sacred places means responding appropriately to…

  1. Creating Sacred Places for Children in Grades 4-6.

    ERIC Educational Resources Information Center

    Fox, Sandra J.

    This guide attempts to help teachers of American Indian children in grades 4-6 provide a culturally relevant education that takes place in the regular classroom, includes content related to Indian students' lives, makes students proud, expands to other experiences, and enhances learning. Creating sacred places means responding appropriately to…

  2. Production of mineral aggregates in quartz tumbling experiments

    NASA Astrophysics Data System (ADS)

    Nørnberg, Per; Finster, Kai; Pall Gunnlaugsson, Haraldur; Knak Jensen, Svend; Merrison, Jonathan Peter

    2013-04-01

    Introduction Tumbling experiments with quartz sand with the purpose of tracing the effect of broken bonds in mineral surfaces resulted in an unexpected production of aggregates. These aggregates are a few microns in diameter, spherical and resembling tiny white "snowballs." Particle comminution by aeolian and other natural weathering processes are known in soil science and is often seen as an increase of fine particles towards the top of soil profiles (Nørnberg, P. 1987, 1988, 2002, J.S. Wright 2007). When mineral grains collide in aeolian processes they break up along weakness zones in the crystal lattice. This mechanism causes broken bonds between atoms in the crystal lattice and results in reactive groups in the mineral surface. This mechanism provides the background for experiments to investigate the oxidation processes of magnetite on the planet Mars. The primary magnetic iron oxide phase on Mars is to day known to be magnetite and the colour of the dust on Mars is most likely due to hematite. To investigate if the oxidation process could take place without going over dissolution and precipitation in water, experiments with tumbling of quartz grains in sealed glass containers along with magnetite were started. The idea was that activated bonds at the surface of quartz could oxidize magnetite and convert it to hematite over time. This proved to be the case (Merrison, J.P. et al. 2010). However, in these experiments we observed the formation of the white aggregates which has been the subject of the study that we present here. Results of tumbling experiments Commercially available quarts (Merck) was sieved to obtain the fraction between 125 and 1000 µm. This fraction was tumbled in glass containers for months and resulted in production of a significant amount of fine grained material (Merrison, J.P et al. 2010). A part of this fine fraction consists of the "snowball"-like aggregates which is a fragile element with relatively high specific surface. The physical

  3. Lithological influence of aggregate in the alkali-carbonate reaction

    SciTech Connect

    Lopez-Buendia, A.M. . E-mail: angel.lopez@aidico.es; Climent, V. . E-mail: vcliment@grupogla.com; Verdu, P.

    2006-08-15

    The reactivity of carbonate rock with the alkali content of cement, commonly called alkali-carbonate reaction (ACR), has been investigated. Alkali-silica reaction (ASR) can also contribute in the alkali-aggregate reaction (AAR) in carbonate rock, mainly due to micro- and crypto-crystalline quartz or clay content in carbonate aggregate. Both ACR and ASR can occur in the same system, as has been also evidenced on this paper. Carbonate aggregate samples were selected using lithological reactivity criteria, taking into account the presence of dedolomitization, partial dolomitization, micro- and crypto-crystalline quartz. Selected rocks include calcitic dolostone with chert (CDX), calcitic dolostone with dedolomitization (CDD), limestone with chert (LX), marly calcitic dolostone with partial dolomitization (CD), high-porosity ferric dolostone with clays (FD). To evaluate the reactivity, aggregates were studied using expansion tests following RILEM AAR-2, AAR-5, a modification using LiOH AAR-5Li was also tested. A complementary study was done using petrographic monitoring with polarised light microscopy on aggregates immersed in NaOH and LiOH solutions after different ages. SEM-EDAX has been used to identify the presence of brucite as a product of dedolomitization. An ACR reaction showed shrinkage of the mortar bars in alkaline solutions explained by induced dedolomitization, while an ASR process typically displayed expansion. Neither shrinkage nor expansion was observed when mortar bars were immersed in solutions of lithium hydroxide. Carbonate aggregate classification with AAR pathology risk has been elaborated based on mechanical behaviours by expansion and shrinkage. It is proposed to be used as a petrographic method for AAR diagnosis to complement the RILEM AAR1 specifically for carbonate aggregate. Aggregate materials can be classified as I (non-reactive), II (potentially reactive), and III (probably reactive), considering induced dedolomitization ACR

  4. 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.

  5. Ash Aggregates in Proximal Settings

    NASA Astrophysics Data System (ADS)

    Porritt, L. A.; Russell, K.

    2012-12-01

    Ash aggregates are thought to have formed within and been deposited by the eruption column and plume and dilute density currents and their associated ash clouds. Moist, turbulent ash clouds are considered critical to ash aggregate formation by facilitating both collision and adhesion of particles. Consequently, they are most commonly found in distal deposits. Proximal deposits containing ash aggregates are less commonly observed but do occur. Here we describe two occurrences of vent proximal ash aggregate-rich deposits; the first within a kimberlite pipe where coated ash pellets and accretionary lapilli are found within the intra-vent sequence; and the second in a glaciovolcanic setting where cored pellets (armoured lapilli) occur within <1 km of the vent. The deposits within the A418 pipe, Diavik Diamond Mine, Canada, are the residual deposits within the conduit and vent of the volcano and are characterised by an abundance of ash aggregates. Coated ash pellets are dominant but are followed in abundance by ash pellets, accretionary lapilli and rare cored pellets. The coated ash pellets typically range from 1 - 5 mm in diameter and have core to rim ratios of approximately 10:1. The formation and preservation of these aggregates elucidates the style and nature of the explosive phase of kimberlite eruption at A418 (and other pipes?). First, these pyroclasts dictate the intensity of the kimberlite eruption; it must be energetic enough to cause intense fragmentation of the kimberlite to produce a substantial volume of very fine ash (<62 μm). Secondly, the ash aggregates indicate the involvement of moisture coupled with the presence of dilute expanded eruption clouds. The structure and distribution of these deposits throughout the kimberlite conduit demand that aggregation and deposition operate entirely within the confines of the vent; this indicates that aggregation is a rapid process. Ash aggregates within glaciovolcanic sequences are also rarely documented. The

  6. Taking the Long View

    ERIC Educational Resources Information Center

    Bennett, Robert B., Jr.

    2010-01-01

    Legal studies faculty need to take the long view in their academic and professional lives. Taking the long view would seem to be a cliched piece of advice, but too frequently legal studies faculty, like their students, get focused on meeting the next short-term hurdle--getting through the next class, grading the next stack of papers, making it…

  7. 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.

  8. Fractal model of consolidation of weakly aggregated colloidal dispersions

    NASA Astrophysics Data System (ADS)

    Potanin, A. A.; Russel, W. B.

    1996-04-01

    A microrheological model for the consolidation of aggregated colloidal dispersion is presented. Interparticle forces are responsible for the formation of the fractal-like network of particles chains. Aggregation is supposed to be weak in that the chains are gradually created and annihilated. In the framework of this model a constitutive equation is proposed which includes linear dependence of the normal stress upon consolidation rate at low stresses and yieldlike behavior as the stress reaches critical value. Our constitutive equation thus generalizes earlier models based on the compressive yield stress concept by taking into account the deformation in the low-compression limit (analog to the Newtonian flow in the low-shear limit). The constitutive equation is employed to calculate numerically concentration profiles of consolidating samples in better agreement with the experimental data for weakly aggregated alumina dispersions.

  9. Mineral trioxide aggregate apexification: A novel approach

    PubMed Central

    Purra, Aamir Rashid; Ahangar, Fayaz Ahmed; Chadgal, Sachin; Farooq, Riyaz

    2016-01-01

    The treatment of choice for necrotic teeth with immature root is apexification, which is induction of apical closure to produce more favorable conditions for conventional root canal filling. The most commonly advocated medicament is calcium hydroxide although recently considerable interest has been expressed in the use of mineral trioxide aggregate (MTA). MTA offers the option of a two-visit apexification procedure so that the fragile tooth can be restored immediately. However, difficulty in placing the material in the wide apical area requires the use of an apical matrix. Materials such as collagen, calcium sulfate, and hydroxyapatite have been used for this purpose. This article describes the use of resorbable suture material to form the apical matrix which offers many advantages over the contemporary materials. PMID:27563191

  10. Mineral trioxide aggregate apexification: A novel approach.

    PubMed

    Purra, Aamir Rashid; Ahangar, Fayaz Ahmed; Chadgal, Sachin; Farooq, Riyaz

    2016-01-01

    The treatment of choice for necrotic teeth with immature root is apexification, which is induction of apical closure to produce more favorable conditions for conventional root canal filling. The most commonly advocated medicament is calcium hydroxide although recently considerable interest has been expressed in the use of mineral trioxide aggregate (MTA). MTA offers the option of a two-visit apexification procedure so that the fragile tooth can be restored immediately. However, difficulty in placing the material in the wide apical area requires the use of an apical matrix. Materials such as collagen, calcium sulfate, and hydroxyapatite have been used for this purpose. This article describes the use of resorbable suture material to form the apical matrix which offers many advantages over the contemporary materials. PMID:27563191

  11. Orion Spacecraft Takes Shape

    NASA Video Gallery

    Technicians move the two halves of the Orion crew exploration vehicle's crew module into place to fuse them together at NASA's Michoud Assembly Facility in New Orleans, La. The Lockheed Martin Orio...

  12. 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…

  13. Give/Take

    SciTech Connect

    2007-09-12

    Give and Take are set of companion utilities that allow a secure transfer of files from one user to another without exposing the files to third parties. The named files are copied to a spool area. The reciever can retrieve the files by running the "take" program. Ownership of the files remains with the giver until they are taken. Certain users may be limited to take files only from specific givers. For these users, files may only be taken from givers who are members of the gt-uid-group where uid is the UNIX id of the limited user.

  14. Give/Take

    2007-09-12

    Give and Take are set of companion utilities that allow a secure transfer of files from one user to another without exposing the files to third parties. The named files are copied to a spool area. The reciever can retrieve the files by running the "take" program. Ownership of the files remains with the giver until they are taken. Certain users may be limited to take files only from specific givers. For these users, filesmore » may only be taken from givers who are members of the gt-uid-group where uid is the UNIX id of the limited user.« less

  15. 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

  16. Novel insights into amylin aggregation

    PubMed Central

    Pillay, Karen; Govender, Patrick

    2014-01-01

    Amylin is a peptide that aggregates into species that are toxic to pancreatic beta cells, leading to type II diabetes. This study has for the first time quantified amylin association and dissociation kinetics (association constant (ka) = 28.7 ± 5.1 L mol−1 s−1 and dissociation constant (kd) = 2.8 ± 0.6 ×10−4 s−1) using surface plasmon resonance (SPR). Thus far, techniques used for the sizing of amylin aggregates do not cater for the real-time monitoring of unconstrained amylin in solution. In this regard we evaluated recently innovated nanoparticle tracking analysis (NTA). In addition, both SPR and NTA were used to study the effect of previously synthesized amylin derivatives on amylin aggregation and to evaluate their potential as a cell-free system for screening potential inhibitors of amylin-mediated cytotoxicity. Results obtained from NTA highlighted a predominance of 100–300 nm amylin aggregates and correlation to previously published cytotoxicity results suggests the toxic species of amylin to be 200–300 nm in size. The results seem to indicate that NTA has potential as a new technique to monitor the aggregation potential of amyloid peptides in solution and also to screen potential inhibitors of amylin-mediated cytotoxicity. PMID:26019498

  17. Teachable Moment: Google Earth Takes Us There

    ERIC Educational Resources Information Center

    Williams, Ann; Davinroy, Thomas C.

    2015-01-01

    In the current educational climate, where clearly articulated learning objectives are required, it is clear that the spontaneous teachable moment still has its place. Authors Ann Williams and Thomas Davinroy think that instructors from almost any discipline can employ Google Earth as a tool to take advantage of teachable moments through the…

  18. Taking a Pulse on Your Practice.

    PubMed

    Hoagland-Smith, Leanne

    2015-01-01

    Each medical practice, like a living organism, occasionally requires reading of its vital signs. As with human beings, one of those vital signs is the pulse. For your medical practice, just like your patients, there are numerous places from which to take that reading. This article reviews seven key pulses that provide insight into what is happening within the workplace culture of your practice.

  19. 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.

  20. Aggregating local image descriptors into compact codes.

    PubMed

    Jégou, Hervé; Perronnin, Florent; Douze, Matthijs; Sánchez, Jorge; Pérez, Patrick; Schmid, Cordelia

    2012-09-01

    This paper addresses the problem of large-scale image search. Three constraints have to be taken into account: search accuracy, efficiency, and memory usage. We first present and evaluate different ways of aggregating local image descriptors into a vector and show that the Fisher kernel achieves better performance than the reference bag-of-visual words approach for any given vector dimension. We then jointly optimize dimensionality reduction and indexing in order to obtain a precise vector comparison as well as a compact representation. The evaluation shows that the image representation can be reduced to a few dozen bytes while preserving high accuracy. Searching a 100 million image data set takes about 250 ms on one processor core.

  1. Take Your Medicines Safely

    MedlinePlus Videos and Cool Tools

    ... better, the antibiotic is working in killing the bacteria, but it might not completely give what they call a "bactericidal effect." That means taking the bacteria completely out of the system. It might be ...

  2. Adjusting to New Places: International Student Adjustment and Place Attachment

    ERIC Educational Resources Information Center

    Terrazas-Carrillo, Elizabeth C.; Hong, Ji Y.; Pace, Terry M.

    2014-01-01

    Using data obtained from in-depth semistructured interviews, we examined international students' attachments to place in the local American Midwestern community where they have attended college for at least 2 years. The results of this study suggest that participants engage in a process of renegotiation of meanings attached to new places in…

  3. Equilibrium structure of ferrofluid aggregates

    SciTech Connect

    Yoon, Mina; Tomanek, David

    2010-01-01

    We study the equilibrium structure of large but finite aggregates of magnetic dipoles, representing a colloidal suspension of magnetite particles in a ferrofluid. With increasing system size, the structural motif evolves from chains and rings to multi-chain and multi-ring assemblies. Very large systems form single- and multi-wall coils, tubes and scrolls. These structural changes result from a competition between various energy terms, which can be approximated analytically within a continuum model. We also study the effect of external parameters such as magnetic field on the relative stability of these structures. Our results may give insight into experimental data obtained during solidification of ferrofluid aggregates at temperatures where thermal fluctuations become negligible in comparison to inter-particle interactions. These data may also help to experimentally control the aggregation of magnetic particles.

  4. Customer Aggregation: An Opportunity for Green Power?

    SciTech Connect

    Holt, E.; Bird, L.

    2001-02-26

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

  5. Fractal aggregates in tennis ball systems

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

    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 images of the cluster of balls, following Forrest and Witten's pioneering studies on the aggregation of smoke particles, to estimate their fractal dimension.

  6. 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.

  7. 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

  8. PLACE NAMES IN THE CLASSROOM.

    ERIC Educational Resources Information Center

    HARDER, KELSIE B.

    ALTHOUGH "PLACE-NAMING" IS A BASIC HUMAN FUNCTION, THE STUDY OF THE ORIGIN OF PROPER NAMES OF PERSONS AND PLACES (ONOMASTICS) HAS BEEN LARGELY IGNORED BY AMERICAN PHILOLOGISTS AND TEACHERS OF ENGLISH. DESPITE A PAUCITY OF RESEARCH, HOWEVER, ANY ENGLISH TEACHER WHO WANTS TO INTEREST STUDENTS IN ONOMASTIC INVESTIGATION CAN EXPLOIT THE GREAT BODY OF…

  9. AGGRESCAN3D (A3D): server for prediction of aggregation properties of protein structures

    PubMed Central

    Zambrano, Rafael; Jamroz, Michal; Szczasiuk, Agata; Pujols, Jordi; Kmiecik, Sebastian; Ventura, Salvador

    2015-01-01

    Protein aggregation underlies an increasing number of disorders and constitutes a major bottleneck in the development of therapeutic proteins. Our present understanding on the molecular determinants of protein aggregation has crystalized in a series of predictive algorithms to identify aggregation-prone sites. A majority of these methods rely only on sequence. Therefore, they find difficulties to predict the aggregation properties of folded globular proteins, where aggregation-prone sites are often not contiguous in sequence or buried inside the native structure. The AGGRESCAN3D (A3D) server overcomes these limitations by taking into account the protein structure and the experimental aggregation propensity scale from the well-established AGGRESCAN method. Using the A3D server, the identified aggregation-prone residues can be virtually mutated to design variants with increased solubility, or to test the impact of pathogenic mutations. Additionally, A3D server enables to take into account the dynamic fluctuations of protein structure in solution, which may influence aggregation propensity. This is possible in A3D Dynamic Mode that exploits the CABS-flex approach for the fast simulations of flexibility of globular proteins. The A3D server can be accessed at http://biocomp.chem.uw.edu.pl/A3D/. PMID:25883144

  10. Studies on recycled aggregates-based concrete.

    PubMed

    Rakshvir, Major; Barai, Sudhirkumar V

    2006-06-01

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

  11. 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. ...

  12. Cyclosporine A enhances platelet aggregation.

    PubMed

    Grace, A A; Barradas, M A; Mikhailidis, D P; Jeremy, J Y; Moorhead, J F; Sweny, P; Dandona, P

    1987-12-01

    In view of the reported increase in thromboembolic episodes following cyclosporine A (CyA) therapy, the effect of this drug on platelet aggregation and thromboxane A2 release was investigated. The addition of CyA, at therapeutic concentrations to platelet rich plasma from normal subjects in vitro was found to increase aggregation in response to adrenaline, collagen and ADP. Ingestion of CyA by healthy volunteers was also associated with enhanced platelet aggregation. The CyA-mediated enhancement of aggregation was further enhanced by the addition in vitro of therapeutic concentrations of heparin. Platelets from renal allograft recipients treated with CyA also showed hyperaggregability and increased thromboxane A2 release, which were most marked at "peak" plasma CyA concentration and less so at "trough" concentrations. Platelet hyperaggregability in renal allograft patients on long-term CyA therapy tended to revert towards normal following the replacement of CyA with azathioprine. Hypertensive patients with renal allografts on nifedipine therapy had normal platelet function and thromboxane release in spite of CyA therapy. These observations suggest that CyA-mediated platelet activation may contribute to the pathogenesis of the thromboembolic phenomena associated with the use of this drug. The increased release of thromboxane A2 (a vasoconstrictor) may also play a role in mediating CyA-related nephrotoxicity.

  13. Sequence-dependent Internalization of Aggregating Peptides*

    PubMed Central

    Couceiro, José R.; Gallardo, Rodrigo; De Smet, Frederik; De Baets, Greet; Baatsen, Pieter; Annaert, Wim; Roose, Kenny; Saelens, Xavier; Schymkowitz, Joost; Rousseau, Frederic

    2015-01-01

    Recently, a number of aggregation disease polypeptides have been shown to spread from cell to cell, thereby displaying prionoid behavior. Studying aggregate internalization, however, is often hampered by the complex kinetics of the aggregation process, resulting in the concomitant uptake of aggregates of different sizes by competing mechanisms, which makes it difficult to isolate pathway-specific responses to aggregates. We designed synthetic aggregating peptides bearing different aggregation propensities with the aim of producing modes of uptake that are sufficiently distinct to differentially analyze the cellular response to internalization. We found that small acidic aggregates (≤500 nm in diameter) were taken up by nonspecific endocytosis as part of the fluid phase and traveled through the endosomal compartment to lysosomes. By contrast, bigger basic aggregates (>1 μm) were taken up through a mechanism dependent on cytoskeletal reorganization and membrane remodeling with the morphological hallmarks of phagocytosis. Importantly, the properties of these aggregates determined not only the mechanism of internalization but also the involvement of the proteostatic machinery (the assembly of interconnected networks that control the biogenesis, folding, trafficking, and degradation of proteins) in the process; whereas the internalization of small acidic aggregates is HSF1-independent, the uptake of larger basic aggregates was HSF1-dependent, requiring Hsp70. Our results show that the biophysical properties of aggregates determine both their mechanism of internalization and proteostatic response. It remains to be seen whether these differences in cellular response contribute to the particular role of specific aggregated proteins in disease. PMID:25391649

  14. Measurement of Lens Protein Aggregation in Vivo Using Dynamic Light Scattering in a Guinea Pig/UVA Model for Nuclear Cataract

    PubMed Central

    Simpanya, M. Francis; Ansari, Rafat R.; Leverenz, Victor; Giblin, Frank J.

    2009-01-01

    The role of UVA radiation in the formation of human nuclear cataract is not well understood. We have previously shown that exposing guinea pigs for 5 months to a chronic low level of UVA light produces increased lens nuclear light scattering and elevated levels of protein disulfide. Here we have used the technique of dynamic light scattering (DLS) to investigate lens protein aggregation in vivo in the guinea pig/UVA model. DLS size distribution analysis conducted at the same location in the lens nucleus of control and UVA-irradiated animals showed a 28% reduction in intensity of small diameter proteins in experimental lenses compared with controls (P < 0.05). In addition, large diameter proteins in UVA-exposed lens nuclei increased five-fold in intensity compared to controls (P < 0.05). The UVA-induced increase in apparent size of lens nuclear small diameter proteins was three-fold (P < 0.01), and the size of large diameter aggregates was more than four-fold in experimental lenses compared with controls. The diameter of crystallin aggregates in the UVA-irradiated lens nucleus was estimated to be 350 nm, a size able to scatter light. No significant changes in protein size were detected in the anterior cortex of UVA-irradiated lenses. It is presumed that the presence of a UVA chromophore in the guinea pig lens (NADPH bound to zeta crystallin), as well as traces of oxygen, contributed to UVA-induced crystallin aggregation. The results indicate a potentially harmful role for UVA light in the lens nucleus. A similar process of UVA-irradiated protein aggregation may take place in the older human lens nucleus, accelerating the formation of human nuclear cataract. PMID:18627516

  15. 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

  16. 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

  17. 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.

  18. Relaxation times and modes of disturbed aggregate distribution in micellar solutions with fusion and fission of micelles

    SciTech Connect

    Zakharov, Anatoly I.; Adzhemyan, Loran Ts.; Shchekin, Alexander K.

    2015-09-28

    We have performed direct numerical calculations of the kinetics of relaxation in the system of surfactant spherical micelles under joint action of the molecular mechanism with capture and emission of individual surfactant molecules by molecular aggregates and the mechanism of fusion and fission of the aggregates. As a basis, we have taken the difference equations of aggregation and fragmentation in the form of the generalized kinetic Smoluchowski equations for aggregate concentrations. The calculations have been made with using the droplet model of molecular surfactant aggregates and two modified Smoluchowski models for the coefficients of aggregate-monomer and aggregate-aggregate fusions which take into account the effects of the aggregate size and presence of hydrophobic spots on the aggregate surface. A full set of relaxation times and corresponding relaxation modes for nonequilibrium aggregate distribution in the aggregation number has been found. The dependencies of these relaxation times and modes on the total concentration of surfactant in the solution and the special parameter controlling the probability of fusion in collisions of micelles with other micelles have been studied.

  19. Taking a Broader View

    ERIC Educational Resources Information Center

    Flannery, Maura C.

    2005-01-01

    A study on stem cells is presented by understanding the environment in which they are found, the support cells and blood vessels as well as the protein scaffolds and other molecules. Researchers found that stem cells in reproductive tissue are surrounded by a pocket of support cells that hold them in place and align them to divide properly, so…

  20. Evolution Takes a Leap

    ERIC Educational Resources Information Center

    Sloan, Bernie

    2005-01-01

    Thirty years ago most resource sharing took place between libraries, with a few formal organizations (library consortia) providing logistical support. Today there are hundreds, perhaps thousands, of organizations around the world facilitating resource sharing. Automation has greatly accelerated the growth of resource sharing. As access to…

  1. SR-71 Taking Off

    NASA Technical Reports Server (NTRS)

    1990-01-01

    One of three U.S. Air Force SR-71 reconnaissance aircraft originally retired from operational service and loaned to NASA for a high-speed research program retracts its landing gear after taking off from NASA's Ames-Dryden Flight Research Facility (later Dryden Flight Research Center), Edwards, California, on a 1990 research flight. One of the SR-71As was later returned to the Air Force for active duty in 1995. Data from the SR-71 high-speed research program will be used to aid designers of future supersonic/hypersonic aircraft and propulsion systems. Two SR-71 aircraft have been used by NASA as testbeds for high-speed and high-altitude aeronautical research. The aircraft, an SR-71A and an SR-71B pilot trainer aircraft, have been based here at NASA's Dryden Flight Research Center, Edwards, California. They were transferred to NASA after the U.S. Air Force program was cancelled. As research platforms, the aircraft can cruise at Mach 3 for more than one hour. For thermal experiments, this can produce heat soak temperatures of over 600 degrees Fahrenheit (F). This operating environment makes these aircraft excellent platforms to carry out research and experiments in a variety of areas -- aerodynamics, propulsion, structures, thermal protection materials, high-speed and high-temperature instrumentation, atmospheric studies, and sonic boom characterization. The SR-71 was used in a program to study ways of reducing sonic booms or over pressures that are heard on the ground, much like sharp thunderclaps, when an aircraft exceeds the speed of sound. Data from this Sonic Boom Mitigation Study could eventually lead to aircraft designs that would reduce the 'peak' overpressures of sonic booms and minimize the startling affect they produce on the ground. One of the first major experiments to be flown in the NASA SR-71 program was a laser air data collection system. It used laser light instead of air pressure to produce airspeed and attitude reference data, such as angle of

  2. Nebular history of amoeboid olivine aggregates

    NASA Astrophysics Data System (ADS)

    Sugiura, N.; Petaev, M. I.; Kimura, M.; Miyazaki, A.; Hiyagon, H.

    2009-05-01

    Minor element (Ca, Cr, and Mn) concentrations in amoeboid olivine aggregates (AOAs) from primitive chondrites were measured and compared with those predicted by equilibrium condensation in the solar nebula. CaO concentrations in forsterite are low, particularly in porous aggregates. A plausible explanation appears that an equilibrium Ca activity was not maintained during the olivine condensation. CaO and MnO in forsterite are negatively correlated, with CaO being higher in compact aggregates. This suggests that the compact aggregates formed either by a prolonged reheating of the porous aggregates or by condensation and aggregation of forsterite during a very slow cooling in the nebula.

  3. Simulating Price-Taking

    ERIC Educational Resources Information Center

    Engelhardt, Lucas M.

    2015-01-01

    In this article, the author presents a price-takers' market simulation geared toward principles-level students. This simulation demonstrates that price-taking behavior is a natural result of the conditions that create perfect competition. In trials, there is a significant degree of price convergence in just three or four rounds. Students find this…

  4. Take Pride in America.

    ERIC Educational Resources Information Center

    Indiana State Dept. of Education, Indianapolis. Center for School Improvement and Performance.

    During the 1987-88 school year the Indiana Department of Education assisted the United States Department of the Interior and the Indiana Department of Natural Resources with a program which asked students to become involved in activities to maintain and manage public lands. The 1987 Take Pride in America (TPIA) school program encouraged volunteer…

  5. Take a Bow

    ERIC Educational Resources Information Center

    Spitzer, Greg; Ogurek, Douglas J.

    2009-01-01

    Performing-arts centers can provide benefits at the high school and collegiate levels, and administrators can take steps now to get the show started. When a new performing-arts center comes to town, local businesses profit. Events and performances draw visitors to the community. Ideally, a performing-arts center will play many roles: entertainment…

  6. Scalable analysis of movement data for extracting and exploring significant places.

    PubMed

    Andrienko, Gennady; Andrienko, Natalia; Hurter, Christophe; Rinzivillo, Salvatore; Wrobel, Stefan

    2013-07-01

    Place-oriented analysis of movement data, i.e., recorded tracks of moving objects, includes finding places of interest in which certain types of movement events occur repeatedly and investigating the temporal distribution of event occurrences in these places and, possibly, other characteristics of the places and links between them. For this class of problems, we propose a visual analytics procedure consisting of four major steps: 1) event extraction from trajectories; 2) extraction of relevant places based on event clustering; 3) spatiotemporal aggregation of events or trajectories; 4) analysis of the aggregated data. All steps can be fulfilled in a scalable way with respect to the amount of the data under analysis; therefore, the procedure is not limited by the size of the computer's RAM and can be applied to very large data sets. We demonstrate the use of the procedure by example of two real-world problems requiring analysis at different spatial scales.

  7. Place recognition using batlike sonar.

    PubMed

    Vanderelst, Dieter; Steckel, Jan; Boen, Andre; Peremans, Herbert; Holderied, Marc W

    2016-01-01

    Echolocating bats have excellent spatial memory and are able to navigate to salient locations using bio-sonar. Navigating and route-following require animals to recognize places. Currently, it is mostly unknown how bats recognize places using echolocation. In this paper, we propose template based place recognition might underlie sonar-based navigation in bats. Under this hypothesis, bats recognize places by remembering their echo signature - rather than their 3D layout. Using a large body of ensonification data collected in three different habitats, we test the viability of this hypothesis assessing two critical properties of the proposed echo signatures: (1) they can be uniquely classified and (2) they vary continuously across space. Based on the results presented, we conclude that the proposed echo signatures satisfy both criteria. We discuss how these two properties of the echo signatures can support navigation and building a cognitive map. PMID:27481189

  8. Place recognition using batlike sonar.

    PubMed

    Vanderelst, Dieter; Steckel, Jan; Boen, Andre; Peremans, Herbert; Holderied, Marc W

    2016-01-01

    Echolocating bats have excellent spatial memory and are able to navigate to salient locations using bio-sonar. Navigating and route-following require animals to recognize places. Currently, it is mostly unknown how bats recognize places using echolocation. In this paper, we propose template based place recognition might underlie sonar-based navigation in bats. Under this hypothesis, bats recognize places by remembering their echo signature - rather than their 3D layout. Using a large body of ensonification data collected in three different habitats, we test the viability of this hypothesis assessing two critical properties of the proposed echo signatures: (1) they can be uniquely classified and (2) they vary continuously across space. Based on the results presented, we conclude that the proposed echo signatures satisfy both criteria. We discuss how these two properties of the echo signatures can support navigation and building a cognitive map.

  9. Role of streams in myxobacteria aggregate formation

    NASA Astrophysics Data System (ADS)

    Kiskowski, Maria A.; Jiang, Yi; Alber, Mark S.

    2004-10-01

    Cell contact, movement and directionality are important factors in biological development (morphogenesis), and myxobacteria are a model system for studying cell-cell interaction and cell organization preceding differentiation. When starved, thousands of myxobacteria cells align, stream and form aggregates which later develop into round, non-motile spores. Canonically, cell aggregation has been attributed to attractive chemotaxis, a long range interaction, but there is growing evidence that myxobacteria organization depends on contact-mediated cell-cell communication. We present a discrete stochastic model based on contact-mediated signaling that suggests an explanation for the initialization of early aggregates, aggregation dynamics and final aggregate distribution. Our model qualitatively reproduces the unique structures of myxobacteria aggregates and detailed stages which occur during myxobacteria aggregation: first, aggregates initialize in random positions and cells join aggregates by random walk; second, cells redistribute by moving within transient streams connecting aggregates. Streams play a critical role in final aggregate size distribution by redistributing cells among fewer, larger aggregates. The mechanism by which streams redistribute cells depends on aggregate sizes and is enhanced by noise. Our model predicts that with increased internal noise, more streams would form and streams would last longer. Simulation results suggest a series of new experiments.

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

    SciTech Connect

    COOPER,J. ARLIN

    1999-09-01

    The methodology in this report improves on some of the limitations of many conventional safety assessment and decision analysis methods. A top-down mathematical approach is developed for decomposing systems and for expressing imprecise individual metrics as possibilistic or fuzzy numbers. A ''Markov-like'' model is developed that facilitates combining (aggregating) inputs into overall metrics and decision aids, also portraying the inherent uncertainty. A major goal of Markov modeling is to help convey the top-down system perspective. One of the constituent methodologies allows metrics to be weighted according to significance of the attribute and aggregated nonlinearly as to contribution. This aggregation is performed using exponential combination of the metrics, since the accumulating effect of such factors responds less and less to additional factors. This is termed ''soft'' mathematical aggregation. Dependence among the contributing factors is accounted for by incorporating subjective metrics on ''overlap'' of the factors as well as by correspondingly reducing the overall contribution of these combinations to the overall aggregation. Decisions corresponding to the meaningfulness of the results are facilitated in several ways. First, the results are compared to a soft threshold provided by a sigmoid function. Second, information is provided on input ''Importance'' and ''Sensitivity,'' in order to know where to place emphasis on considering new controls that may be necessary. Third, trends in inputs and outputs are tracked in order to obtain significant information% including cyclic information for the decision process. A practical example from the air transportation industry is used to demonstrate application of the methodology. Illustrations are given for developing a structure (along with recommended inputs and weights) for air transportation oversight at three different levels, for developing and using cycle information, for developing Importance and

  11. Spatial patterns of African ungulate aggregation reveal complex but limited risk effects from reintroduced carnivores.

    PubMed

    Moll, Remington J; Killion, Alexander K; Montgomery, Robert A; Tambling, Craig J; Hayward, Matt W

    2016-05-01

    The "landscape of fear" model, recently advanced in research on the non-lethal effects of carnivores on ungulates, predicts that prey will exhibit detectable antipredator behavior not only during risky times (i.e., predators in close proximity) but also in risky places (i.e., habitat where predators kill prey or tend to occur). Aggregation is an important antipredator response in numerous ungulate species, making it a useful metric to evaluate the strength and scope of the landscape of fear in a multi-carnivore, multi-ungulate system. We conducted ungulate surveys over a 2-year period in South Africa to test the influence of three broad-scale sources of variation in the landscape on spatial patterns in aggregation: (1) habitat structure, (2) where carnivores tended to occur (i.e., population-level utilization distributions), and (3) where carnivores tended to kill ungulate prey (i.e., probabilistic kill site maps). We analyzed spatial variation in aggregation for six ungulate species exposed to predation from recently reintroduced lion (Panthera leo) and spotted hyena (Crocuta crocuta). Although we did detect larger aggregations of ungulates in "risky places," these effects existed primarily for smaller-bodied (<150 kg) ungulates and were relatively moderate (change of 4 individuals across all habitats). In comparison, ungulate aggregations tended to increase at a slightly lower rate in habitat that was more open. The lion, an ambush (stalking) carnivore, had stronger influence on ungulate aggregation than the hyena, an active (coursing) carnivore. In addition, places where lions tended to kill prey had a greater effect on ungulate aggregation than places where lions tended to occur, but an opposing pattern existed for hyena. Our study reveals heterogeneity in the landscape of fear and suggests broad-scale risk effects following carnivore reintroduction only moderately influence ungulate aggregation size and vary considerably by predator hunting mode, type of

  12. Spatial patterns of African ungulate aggregation reveal complex but limited risk effects from reintroduced carnivores.

    PubMed

    Moll, Remington J; Killion, Alexander K; Montgomery, Robert A; Tambling, Craig J; Hayward, Matt W

    2016-05-01

    The "landscape of fear" model, recently advanced in research on the non-lethal effects of carnivores on ungulates, predicts that prey will exhibit detectable antipredator behavior not only during risky times (i.e., predators in close proximity) but also in risky places (i.e., habitat where predators kill prey or tend to occur). Aggregation is an important antipredator response in numerous ungulate species, making it a useful metric to evaluate the strength and scope of the landscape of fear in a multi-carnivore, multi-ungulate system. We conducted ungulate surveys over a 2-year period in South Africa to test the influence of three broad-scale sources of variation in the landscape on spatial patterns in aggregation: (1) habitat structure, (2) where carnivores tended to occur (i.e., population-level utilization distributions), and (3) where carnivores tended to kill ungulate prey (i.e., probabilistic kill site maps). We analyzed spatial variation in aggregation for six ungulate species exposed to predation from recently reintroduced lion (Panthera leo) and spotted hyena (Crocuta crocuta). Although we did detect larger aggregations of ungulates in "risky places," these effects existed primarily for smaller-bodied (<150 kg) ungulates and were relatively moderate (change of 4 individuals across all habitats). In comparison, ungulate aggregations tended to increase at a slightly lower rate in habitat that was more open. The lion, an ambush (stalking) carnivore, had stronger influence on ungulate aggregation than the hyena, an active (coursing) carnivore. In addition, places where lions tended to kill prey had a greater effect on ungulate aggregation than places where lions tended to occur, but an opposing pattern existed for hyena. Our study reveals heterogeneity in the landscape of fear and suggests broad-scale risk effects following carnivore reintroduction only moderately influence ungulate aggregation size and vary considerably by predator hunting mode, type of

  13. 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

  14. Protein aggregation in salt solutions.

    PubMed

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

    2015-05-26

    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.

  15. Risk of bleeding after dentoalveolar surgery in patients taking anticoagulants.

    PubMed

    Broekema, Ferdinand I; van Minnen, Baucke; Jansma, Johan; Bos, Rudolf R M

    2014-03-01

    To avoid increasing the risk of thromboembolic events, it is recommended that treatment with anticoagulants should be continued during dentoalveolar operations. We have evaluated the incidence of bleeding after dentoalveolar operations in a prospective study of 206 patients, 103 who were, and 103 who were not, taking anticoagulants. Seventy-one were taking thrombocyte aggregation inhibitors and 32 vitamin K antagonists. Patients were treated according to guidelines developed at the Academic Centre for Dentistry Amsterdam (ACTA), The Netherlands. The operations studied included surgical extraction (when the surgeon had to incise the gingiva before extraction), non-surgical extraction, apicectomy, and placement of implants. Patients were given standard postoperative care and those taking vitamin K antagonists used tranexamic acid mouthwash postoperatively. No patient developed a severe bleed that required intervention. Seven patients (7%) taking anticoagulants developed mild postoperative bleeds. Patients taking vitamin K antagonists reported 3 episodes (9%) compared with 4 (6%) in the group taking thrombocyte aggregation inhibitors. Among patients not taking anticoagulants, two (2%) developed mild bleeding. The differences between the groups were not significant. All bleeding was controlled by the patients themselves with compression with gauze. We conclude that dentoalveolar surgery is safe in patients being treated with anticoagulants provided that the conditions described in the ACTA guidelines are met. PMID:24485810

  16. Take the "C" Train

    ERIC Educational Resources Information Center

    Lawton, Rebecca

    2008-01-01

    In this essay, the author recalls several of her experiences in which she successfully pulled her boats out of river holes by throwing herself to the water as a sea-anchor. She learned this trick from her senior guides at a spring training. Her guides told her, "When you're stuck in a hole, take the "C" train."" "Meaning?" The author asked her…

  17. Precipitation Aggregation and the Local Environment

    NASA Astrophysics Data System (ADS)

    Smalley, Mark

    The details of large-scale spatial structures of precipitation have only recently become apparent with the advent of high-resolution near-global observations from space-borne radars. As such, the relationships between these structures and the local environment and global climate are just beginning to emerge in the scientific community. Precipitation aggregates on a wide variety of scales, from individual boundary layer instabilities to extra-tropical cyclones. Separate aggregation states have been associated with widely varying precipitation rates and atmospheric states, motivating the inclusion of spatial information in hydrologic and climate models. This work adds to the body of knowledge surrounding large-scale precipitation aggregation and its driving factors by describing and demonstrating a new method of defining the spatial characteristics of precipitation events. The analysis relies on the high sensitivity and high resolution of the CloudSat Cloud Profiling Radar for the identification of precipitation with near-global coverage. The method is based on the dependence of the probability of precipitation on search area, or spatial resolution. Variations in this relationship are caused by variations in the principal characteristics of event spatial patterns: the relative spacing between events, the number density of events, and the overall fraction of precipitating scenes at high resolution. Here, this relationship is modeled by a stretched exponential containing two coefficients, that are shown to depict seasonal general circulation patterns as well as local weather. NASA's Modern-Era Retrospective analysis for Research and Applications is then used to place those spatial characteristics in the context of the local and large-scale environment. At regional scale, precipitation event density during the Amazon wet season is shown to be dependent on zonal wind speed. On a global scale, the relative spacing of shallow oceanic precipitation depends on the

  18. John Dewey and a Pedagogy of Place

    ERIC Educational Resources Information Center

    Jayanandhan, Stephanie Raill

    2009-01-01

    If asked to define the idea of "place" one might struggle. Yet people across time and cultures readily share examples of important places or safe places or "foreign" places with one another and offer heartfelt descriptions in literature and art of childhood places, favorite places, strange places. Akinbola Akinwumi, paraphrasing Yi-Fu Tuan,…

  19. 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.

  20. A qualitative model for aggregation and diffusion of β-amyloid in Alzheimer's disease.

    PubMed

    Achdou, Yves; Franchi, Bruno; Marcello, Norina; Tesi, Maria Carla

    2013-12-01

    In this paper we present a mathematical model for the aggregation and diffusion of Aβ amyloid in the brain affected by Alzheimer's disease, at the early stage of the disease. The model is based on a classical discrete Smoluchowski aggregation equation modified to take diffusion into account. We also describe a numerical scheme and discuss the results of the simulations in the light of the recent biomedical literature.

  1. 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.

  2. Soft Mathematical Aggregation in Safety Assessment and Decision Analysis

    SciTech Connect

    Cooper, J. Arlin

    1999-06-10

    This paper improves on some of the limitations of conventional safety assessment and decision analysis methods. It develops a top-down mathematical method for expressing imprecise individual metrics as possibilistic or fuzzy numbers and shows how they may be combined (aggregated) into an overall metric, also portraying the inherent uncertainty. Both positively contributing and negatively contributing factors are included. Metrics are weighted according to significance of the attribute and evaluated as to contribution toward the attribute. Aggregation is performed using exponential combination of the metrics, since the accumulating effect of such factors responds less and less to additional factors. This is termed soft mathematical aggregation. Dependence among the contributing factors is accounted for by incorporating subjective metrics on overlap of the factors and by correspondingly reducing the overall contribution of these combinations to the overall aggregation. Decisions corresponding to the meaningfulness of the results are facilitated in several ways. First, the results are compared to a soft threshold provided by a sigmoid function. Second, information is provided on input ''Importance'' and ''Sensitivity,'' in order to know where to place emphasis on controls that may be necessary. Third, trends in inputs and outputs are tracked in order to add important information to the decision process. The methodology has been implemented in software.

  3. Ex vivo human platelet aggregation induced by decompression during reduced barometric pressure, hydrostatic, and hydrodynamic (Bernoulli) effect.

    PubMed

    Murayama, M

    1984-03-01

    Decompression of human platelet-rich plasma (PRP) in siliconized glass or plastic to 380 mm Hg for 3 hours at 38 degrees C produced platelet aggregation independent of pO2. Aggregation also took place when PRP was compressed to 8,000 PSI and then decompressed slowly to one atmosphere (14.7 PSI) without gas bubble formation. Platelets also aggregated when plasma was decompressed hydrodynamically (Bernoulli effect) at room temperature. It was also found that the drugs piracetam (2-oxypyrolidine acetamide) and pentoxifylline (1-(5-oxohexyl)-theobromine) at 0.5 and 1.0 mM prevent thrombocyte aggregation. Implications for mountain sickness are discussed.

  4. The Path Is Place: Skateboarding, Graffiti and Performances of Place

    ERIC Educational Resources Information Center

    Ong, Adelina

    2016-01-01

    This article reflects on two performances of place involving graffiti and skateboarding: the first looks at a graffiti intervention by SKL0, an urban artist in Singapore, and the second examines the "Long Live Southbank" ("LLSB") campaign to resist the relocation of Southbank's Undercroft, an appropriated skate space in London.…

  5. 76 FR 58473 - Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-21

    ... area in less than 1.8 m of water. The proposed survey will take place on Apache's leases in Cook Inlet... in deeper water is called Ocean Bottom Receiver Location, which uses a small volume air gun (10 in\\3... terms of SEL than from the single water gun impulse (estimated at 188 dB re 1 Pa\\2\\-s) in...

  6. Disruption patterns of rotating self-gravitating aggregates: A survey on angle of friction and tensile strength

    NASA Astrophysics Data System (ADS)

    Sánchez, Paul; Scheeres, Daniel J.

    2016-06-01

    This paper presents a study, through the use of a SSDEM simulation code, of the possible disruption patterns and mechanisms of self-gravitating aggregates that are spun-up to the point of disruption. We do this survey by systematically changing the angle of friction and tensile stress of the aggregates. It is observed that the amount of deformation that takes place before disruption, as well as its onset, is directly related to the angle of friction. On the other hand, the change in tensile strength allows us to clearly observe a continuous transition from losing surface material to larger scale fission at higher spin rates before disruption, but in no case do we observe surface flow. These results are also compared to other simulation results and the observations of asteroids P/2013 R3, P/2013 P5, 1950 DA, 1999 KW4 and Geographos. Additionally, we propose modifications to previously discussed mechanisms for the formation of binary asteroids and asteroid pairs.

  7. Get3 is a holdase chaperone and moves to deposition sites for aggregated proteins when membrane targeting is blocked

    PubMed Central

    Powis, Katie; Schrul, Bianca; Tienson, Heather; Gostimskaya, Irina; Breker, Michal; High, Stephen; Schuldiner, Maya; Jakob, Ursula; Schwappach, Blanche

    2013-01-01

    Summary The endomembrane system of yeast contains different tail-anchored proteins that are post-translationally targeted to membranes via their C-terminal transmembrane domain. This hydrophobic segment could be hazardous in the cytosol if membrane insertion fails, resulting in the need for energy-dependent chaperoning and the degradation of aggregated tail-anchored proteins. A cascade of GET proteins cooperates in a conserved pathway to accept newly synthesized tail-anchored proteins from ribosomes and guide them to a receptor at the endoplasmic reticulum, where membrane integration takes place. It is, however, unclear how the GET system reacts to conditions of energy depletion that might prevent membrane insertion and hence lead to the accumulation of hydrophobic proteins in the cytosol. Here we show that the ATPase Get3, which accommodates the hydrophobic tail anchor of clients, has a dual function: promoting tail-anchored protein insertion when glucose is abundant and serving as an ATP-independent holdase chaperone during energy depletion. Like the generic chaperones Hsp42, Ssa2, Sis1 and Hsp104, we found that Get3 moves reversibly to deposition sites for protein aggregates, hence supporting the sequestration of tail-anchored proteins under conditions that prevent tail-anchored protein insertion. Our findings support a ubiquitous role for the cytosolic GET complex as a triaging platform involved in cellular proteostasis. PMID:23203805

  8. Controlling the formation of cyanine dye H- and J-aggregates with cucurbituril hosts in the presence of anionic polyelectrolytes.

    PubMed

    Gadde, Suresh; Batchelor, Elizabeth K; Kaifer, Angel E

    2009-06-01

    The presence of anionic polyelectrolytes enhances the tendency of cationic cyanine dyes to form aggregates in aqueous media. In this work we investigate the interactions between two cyanine dyes, pseudoisocyanine (PIC) and pinacyanol (PIN), with polystyrenesulfonate (PSS) as the key additive to develop J- and H-aggregates. We also take advantage of the binding properties of the cucurbit[7]uril (CB7) host to control formation of these aggregates through its host-guest interactions with the dye molecules. UV/Vis absorption spectroscopic studies clearly demonstrate the PSS-enhanced formation of J-aggregates in the case of PIC and H-aggregates in the case of PIN. Electrostatic interactions between the cyanine dye molecules and the polyelectrolyte chains assist the formation of J- or H-aggregates at very low dye concentrations (ca. 10 microM). Optimum development of dye aggregates was observed at a sulfonate/dye molar ratio of about 3:1. Departures from this stoichiometric ratio seem to perturb the optimal aggregate structure. Furthermore, the presence of CB7 was found to effectively disrupt the interactions responsible for dye aggregation. Thus, CB7 completely disrupts the J-aggregates formed by PIC and the H-aggregates (as well as lower concentrations of J-aggregates) formed by PIN. UV/Vis and emission spectroscopic studies clearly indicate that binding of CB7 to both dye molecules removes them from the aggregate structures. Our spectroscopic data clearly indicate that regulation of the relative molar ratios of dye, CB7 host, and polyelectrolyte sulfonate groups leads to a quantitative control of dye aggregation, yielding variable amounts of PIC J- and PIN H-aggregates in these solutions. PMID:19402091

  9. Formation of Reversible Clusters with Controlled Degree of Aggregation.

    PubMed

    Lotfizadeh, Saba; Aljama, Hassan; Reilly, Dan; Matsoukas, Themis

    2016-05-17

    We develop a reversible colloidal system of silica nanoparticles whose state of aggregation is controlled reproducibly from a state of fully dispersed nanoparticles to that of a colloidal gel and back. The surface of silica nanoparticles is coated with various amino silanes to identify a silane capable of forming a monolayer on the surface of the particles without causing irreversible aggregation. Of the three silanes used in this study, N-[3-(trimethoxysilyl)propyl]ethylenediamine was found to be capable of producing monolayers up to full surface coverage without inducing irreversible aggregation of the nanoparticles. At near full surface coverage the electrokinetic behavior of the functionalized silica is completely determined by that of the aminosilane. At acidic pH the ionization of the amino groups provides electrosteric stabilization and the system is fully dispersed. At basic pH, the dispersion state is dominated by the hydrophobic interaction between the uncharged aminosilane chains in the aqueous environment and the system forms a colloidal gel. At intermediate pH values the dispersion state is dominated by the balance between electrostatic and hydrophobic interactions, and the system exists in clusters whose size is determined solely by the pH. The transformation between states of aggregation is reversible and a reproducible function of pH. The rate of gelation can be controlled to be as fast as minutes while deaggregation is much slower and takes several hours to complete. PMID:27124089

  10. Microbial life in variably saturated soil aggregates - upscaling gaseous fluxes across distributed aggregate sizes in a soil profile

    NASA Astrophysics Data System (ADS)

    Or, D.; Ebrahimi, A.

    2015-12-01

    Recent studies revealed highly dynamic and rich behavior of microbial communities inhabiting soil aggregates. Modeling of these processes in three dimensional (unsaturated) pore networks provided insights into the unique conditions essential for coexistence of oxic and anoxic microsites that shape (and respond to) aerobic and anaerobic microbial communities. Soil hydration dynamics continuously alter the spatial extent of anoxic niches (hotspots) that flicker in time (hot moments) and support anaerobic microbial activity even in unsaturated and oxic soil profiles. We extend a model for individual-based microbial community growth in 3-D angular pore networks mimicking soil aggregates of different sizes placed in different ambient boundary conditions reflecting profiles of water, carbon, and oxygen in soil. An upscaling scheme was developed to account for aerobic and anaerobic activity within each aggregate class size and soil depth integrated over the aggregate size distribution in the soil for a range of hydration conditions. Results show that dynamic adjustments in microbial community composition affect CO2 and N2O production rates in good agreement with experimental data. The modeling approach addresses a long-standing challenge of linking hydration conditions to dynamic adjustments of microbial communities within "hotspots" with the emergence of "hot moments" reflecting high rates of denitrification and organic matter decomposition.

  11. Mucilaginous aggregates in the northern Adriatic in the period 1999-2002: typology and distribution.

    PubMed

    Precali, Robert; Giani, Michele; Marini, Mauro; Grilli, Federica; Ferrari, Carla R; Pecar, Osvin; Paschini, Elio

    2005-12-15

    The spatial and temporal distributions of different types of visible mucilaginous aggregates were investigated monthly by underwater video cameras in the northern Adriatic (NA) from June 1999 to July 2002. Small aggregates (flocs, macroflocs and stringers) were observed in all seasons with higher values in autumn and winter. Larger aggregates (ribbons, cobwebs, clouds, and false bottoms) formed only during late-spring and summer, particularly in 2000 and 2002, when the seasonal thermohaline stratification was marked. In fact, the process of mucilage formation took place mainly in the upper water column, above the main pycnocline. The spatial distribution shows that higher concentrations of small aggregates occur in the more productive coastal waters. The larger aggregates form or accumulate mainly in coastal waters in the southern part of the NA and in the central part of the Po River delta-Rovinj transect, where a gyre greatly influences the aggregates distribution. The fronts between low salinity coastal waters and high salinity waters of southern origin play an important role for accumulation and aggregation of the mucilage during spring and summer. Most of the aggregates accumulate in correspondence with strong pycnoclines with differences in density anomaly of 2 kg m(-3) or higher. False bottoms formed in correspondence with strong haloclines (DeltaS congruent with 2), while cobwebs and ribbons also occurred when the halocline was less marked (DeltaS<0.5). Meteorological conditions greatly influenced the aggregate formation. Calm weather and weak winds favour aggregation processes, while strong north-easterly winds, causing intense mixing, result in the dispersion of the mucilaginous aggregates, as occurred during the Bora event in July 2000.

  12. Mucilaginous aggregates in the northern Adriatic in the period 1999-2002: typology and distribution.

    PubMed

    Precali, Robert; Giani, Michele; Marini, Mauro; Grilli, Federica; Ferrari, Carla R; Pecar, Osvin; Paschini, Elio

    2005-12-15

    The spatial and temporal distributions of different types of visible mucilaginous aggregates were investigated monthly by underwater video cameras in the northern Adriatic (NA) from June 1999 to July 2002. Small aggregates (flocs, macroflocs and stringers) were observed in all seasons with higher values in autumn and winter. Larger aggregates (ribbons, cobwebs, clouds, and false bottoms) formed only during late-spring and summer, particularly in 2000 and 2002, when the seasonal thermohaline stratification was marked. In fact, the process of mucilage formation took place mainly in the upper water column, above the main pycnocline. The spatial distribution shows that higher concentrations of small aggregates occur in the more productive coastal waters. The larger aggregates form or accumulate mainly in coastal waters in the southern part of the NA and in the central part of the Po River delta-Rovinj transect, where a gyre greatly influences the aggregates distribution. The fronts between low salinity coastal waters and high salinity waters of southern origin play an important role for accumulation and aggregation of the mucilage during spring and summer. Most of the aggregates accumulate in correspondence with strong pycnoclines with differences in density anomaly of 2 kg m(-3) or higher. False bottoms formed in correspondence with strong haloclines (DeltaS congruent with 2), while cobwebs and ribbons also occurred when the halocline was less marked (DeltaS<0.5). Meteorological conditions greatly influenced the aggregate formation. Calm weather and weak winds favour aggregation processes, while strong north-easterly winds, causing intense mixing, result in the dispersion of the mucilaginous aggregates, as occurred during the Bora event in July 2000. PMID:16289713

  13. Physics Take-Outs

    NASA Astrophysics Data System (ADS)

    Riendeau, Diane; Hawkins, Stephanie; Beutlich, Scott

    2016-03-01

    Most teachers want students to think about their course content not only during class but also throughout their day. So, how do you get your students to see how what they learn in class applies to their lives outside of class? As physics teachers, we are fortunate that our students are continually surrounded by our content. How can we get them to notice the physics around them? How can we get them to make connections between the classroom content and their everyday lives? We would like to offer a few suggestions, Physics Take-Outs, to solve this problem.

  14. Why It Takes Prevention, Not Detection, to Fight Bioterrorism

    ERIC Educational Resources Information Center

    Janata, Jiri (Art)

    2005-01-01

    Following the events which took place on September 11, 2001, and the anthrax attacks which occurred after that date, US authorities became concerned with the idea that an assault with chemical or biological weapons could take place on American territory or in American ships or planes. A worrisome model for such an assault was the 1995 terrorist…

  15. Correlates of Intellectual Risk Taking in Elementary School Science

    ERIC Educational Resources Information Center

    Beghetto, Ronald A.

    2009-01-01

    This study had the goal of exploring factors associated with elementary students' (N = 585) reports of intellectual risk taking in science. Intellectual risk taking (IRT) was defined as engaging in adaptive learning behaviors (sharing tentative ideas, asking questions, attempting to do and learn new things) that placed the learner at risk of…

  16. 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.

  17. 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.

  18. Changes in fractal dimension during aggregation.

    PubMed

    Chakraborti, Rajat K; Gardner, Kevin H; Atkinson, Joseph F; Van Benschoten, John E

    2003-02-01

    Experiments were performed to evaluate temporal changes in the fractal dimension of aggregates formed during flocculation of an initially monodisperse suspension of latex microspheres. Particle size distributions and aggregate geometrical information at different mixing times were obtained using a non-intrusive optical sampling and digital image analysis technique, under variable conditions of mixing speed, coagulant (alum) dose and particle concentration. Pixel resolution required to determine aggregate size and geometric measures including the fractal dimension is discussed and a quantitative measure of accuracy is developed. The two-dimensional fractal dimension was found to range from 1.94 to 1.48, corresponding to aggregates that are either relatively compact or loosely structured, respectively. Changes in fractal dimension are explained using a conceptual model, which describes changes in fractal dimension associated with aggregate growth and changes in aggregate structure. For aggregation of an initially monodisperse suspension, the fractal dimension was found to decrease over time in the initial stages of floc formation.

  19. A Place on the Shelf

    ERIC Educational Resources Information Center

    Thomas, Devon

    2007-01-01

    If we read to discover new worlds, we also read to find ourselves. For gays and lesbians, this act of discovery can be problematic: literature has so often excluded them. In the last decades, as gays and lesbians have grown increasingly vocal in the effort to secure their rightful place in society, a broad range of fiction has emerged that…

  20. Creative Teaching with Historic Places.

    ERIC Educational Resources Information Center

    Greenberg, Ronald M., Ed.

    2000-01-01

    This journal contains articles and materials to help teachers instruct students about U.S. historical and cultural heritage. Articles and teaching materials are: "History in the Hands of Tomorrow's Citizens" (C. D. Shull; B. M. Boland); "On-Site Learning--The Power of Historic Places" (J. O. Horton); "Visualizing History--Inquiring Minds Want To…

  1. Place learning by mechanical contact.

    PubMed

    Harrison, Steven J; Turvey, Michael T

    2010-05-01

    For some animals (e.g. the night-active wandering spider) the encounters with the habitat that result in place learning are predominantly mechanical. We asked whether place learning limited to mechanical contact, like place learning in general, entails vectors tied to individual landmarks and relations between landmarks. We constructed minimal environments for blindfolded human participants. Landmarks were raised steps. 'Home' was a mechanically indistinct location. Travel was linear. The mechanical contacts were those of walking, stepping, and probing with a soft-tipped cane. Home-orienting activities preceded tests of finding home from a given location with landmarks unchanged or (unbeknown to participants) shifted. In a one-landmark environment, perceived home shifted in the same direction, with the same magnitude, as the shifted landmark. In an environment of two landmarks located in the same direction from home, shifting the further landmark toward home resulted in a change in home's perceived location that preserved the original ratio of distances separating home, nearer landmark, and further landmark. Both findings were invariant over the travel route to the test location and repetitions of testing. It seems, therefore, that for humans (and, perhaps, for wandering spiders), mechanical contact can reveal the vectors and relations specifying places.

  2. The Mushroom Place. Part III.

    ERIC Educational Resources Information Center

    Schlichter, Carol

    1978-01-01

    The final installment of a series of articles on the "Mushroom Place" learning center program, which involves creative thinking activities for young, gifted students, describes "Doing It the Hard Way," a performance task which involves the actual construction of objects from a selected set of materials in the absence of the usual project tools.…

  3. Sense of Place in Appalachia.

    ERIC Educational Resources Information Center

    Arnow, Pat, Ed.

    1989-01-01

    This journal issue contains interviews, essays, short stories, and poetry focusing on sense of place in Appalachia. In interviews, author Wilma Dykeman discussed past and recent novels set in Appalachia with interviewer Sandra L. Ballard; and novelist Lee Smith spoke with interviewer Pat Arnow about how Appalachia has shaped her writing. Essays…

  4. Place recognition using batlike sonar

    PubMed Central

    Vanderelst, Dieter; Steckel, Jan; Boen, Andre; Peremans, Herbert; Holderied, Marc W

    2016-01-01

    Echolocating bats have excellent spatial memory and are able to navigate to salient locations using bio-sonar. Navigating and route-following require animals to recognize places. Currently, it is mostly unknown how bats recognize places using echolocation. In this paper, we propose template based place recognition might underlie sonar-based navigation in bats. Under this hypothesis, bats recognize places by remembering their echo signature - rather than their 3D layout. Using a large body of ensonification data collected in three different habitats, we test the viability of this hypothesis assessing two critical properties of the proposed echo signatures: (1) they can be uniquely classified and (2) they vary continuously across space. Based on the results presented, we conclude that the proposed echo signatures satisfy both criteria. We discuss how these two properties of the echo signatures can support navigation and building a cognitive map. DOI: http://dx.doi.org/10.7554/eLife.14188.001 PMID:27481189

  5. The in vitro effect of aspirin on increased whole blood platelet aggregation in oral contraceptive users.

    PubMed

    Norris, L A; Bonnar, J

    1994-05-01

    The effects of triphasic oral contraceptives on whole blood platelet aggregation in 36 Italian women are reported here. Aspirin's effects on platelet aggregation were also studied. 18 women took a triphasic oral contraceptive; 10 women took Trinordiol, while 8 took Trinovum for at least 90 days. The remaining 18 women took nothing and served as controls. The study was aligned with each woman's birth control pill cycle. Blood was taken daily on days 15-21 of their cycle. Either saline solution or acetylsalicylic acid was added to the blood samples and compared. All data was statistically analyzed using unpaired student's t-test. Effects of 3 aggregating agents, ADP, PAF, and EDTA, on platelet aggregation were studied. Arachidonic acid and adrenalin bitartrate were also studied in this manner. An increase in platelet aggregation was observed in women taking oral contraceptives. No difference was found between patients taking Trinordiol and those taking Trinovum. The results of this study indicate an increase in whole blood platelet sensitivity to collagen, adrenalin, and arachidonic acid when using oral contraceptives. Aspirin, at low doses, may have a role in preventing early thrombus formation in women taking oral contraceptives. PMID:8042198

  6. [Risk-taking behaviors among young people].

    PubMed

    Le Breton, David

    2004-01-01

    Risk-taking behaviors are often an ambivalent way of calling for help from close friends or family - those who count. It is an ultimate means of finding meaning and a system of values; it is a sign of an adolescent's active resistance and attempts to re-establish his or her place in the world. It contrasts with the far more incisive risk of depression and the radical collapse of meaning. In spite of the suffering it engenders, risk-taking nevertheless has a positive side, fostering independence in adolescents and a search for reference points. It leads to a better self-image and is a means of developing one's identity. It is nonetheless painful in terms of its repercussions in terms of injuries, death or addiction. The turbulence caused by risk-taking behaviors illustrates a determination to be rid of one's suffering and to fight on so that life can, at last, be lived. PMID:15918660

  7. The place of care in ethical theory.

    PubMed

    Veatch, R M

    1998-04-01

    The concept of care and a related ethical theory of care have emerged as increasingly important in biomedical ethics. This essay outlines a series of questions about the conceptualization of care and its place in ethical theory. First, it considers the possibility that care should be conceptualized as an alternative principle of right action; then as a virtue, a cluster of virtues, or as a synonym for virtue theory. The implications for various interpretations of the debate of the relation of care and justice are then explored, suggesting three possible meanings for that contrast. Next, the possibility that care theorists are taking up the debate over the relation between principles and cases is considered. Finally, it is suggested that care theorists may be pressing for consideration of an entirely new question in moral theory: the assessment of the normative appropriateness of relationships. Issues needing to be addressed in an ethic of relationships are suggested.

  8. The Magical Place Called Opera.

    ERIC Educational Resources Information Center

    Raplenovich, Kay

    1996-01-01

    "Create Your Own," month-long "Artist in Education" residencies sponsored by the Ohio Arts Council, are used to guide students and teachers through the process of taking the vision of an original opera conceived by students and turning it into a reality. A local opera company is actually created. "Create Your Own" shows children that opera can be…

  9. There's No Place Like School.

    ERIC Educational Resources Information Center

    Fagan, Juanita

    2001-01-01

    In 1998, the principal of a rural Oregon elementary school used a 21st Century Community Learning Centers grant and Title I funds to design a program to address homeless children's personal and social well-being. Kids eat a nutritious breakfast, take showers, get clothes washed, receive positive feedback, and participate in after-school…

  10. 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.

  11. Familial Aggregation of Absolute Pitch

    PubMed Central

    Baharloo, Siamak; Service, Susan K.; Risch, Neil; Gitschier, Jane; Freimer, Nelson B.

    2000-01-01

    Absolute pitch (AP) is a behavioral trait that is defined as the ability to identify the pitch of tones in the absence of a reference pitch. AP is an ideal phenotype for investigation of gene and environment interactions in the development of complex human behaviors. Individuals who score exceptionally well on formalized auditory tests of pitch perception are designated as “AP-1.” As described in this report, auditory testing of siblings of AP-1 probands and of a control sample indicates that AP-1 aggregates in families. The implications of this finding for the mapping of loci for AP-1 predisposition are discussed. PMID:10924408

  12. Microgravity Smoldering Combustion Takes Flight

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Microgravity Smoldering Combustion (MSC) experiment lifted off aboard the Space Shuttle Endeavour in September 1995 on the STS-69 mission. This experiment is part of series of studies focused on the smolder characteristics of porous, combustible materials in a microgravity environment. Smoldering is a nonflaming form of combustion that takes place in the interior of combustible materials. Common examples of smoldering are nonflaming embers, charcoal briquettes, and cigarettes. The objective of the study is to provide a better understanding of the controlling mechanisms of smoldering, both in microgravity and Earth gravity. As with other forms of combustion, gravity affects the availability of air and the transport of heat, and therefore, the rate of combustion. Results of the microgravity experiments will be compared with identical experiments carried out in Earth's gravity. They also will be used to verify present theories of smoldering combustion and will provide new insights into the process of smoldering combustion, enhancing our fundamental understanding of this frequently encountered combustion process and guiding improvement in fire safety practices.

  13. Nonlinear refraction of silver hydrosols during their aggregation

    SciTech Connect

    Karpov, S V; Kodirov, M K; Ryasnyansky, A I; Slabko, V V

    2001-10-31

    The relation between the degree of aggregation of silver hydrosols and their nonlinear refractive index n{sub 2} is studied experimentally. It is found that the sign of n{sub 2} at a wavelength of 1.064 {mu}m changes with increasing the aggregation degree, which corresponds to the replacing of self-focusing by self-defocusing. The observed effects are explained based on the analysis of a change in nonlinear dispersion of the medium, taking into account the interaction between phases and the photochromic effects, which are typical for colloidal structures with fractal geometry. It is shown that the change in the sign of the nonlinear refractive index of hydrosols upon irradiation by laser pulses of duration of less than 10{sup -7} s is caused by the perturbation of resonances of silver and water and by the competition between Kerr nonlinear polarisations involving these resonances. (nonlinear optical phenomena and devices)

  14. A local PDE model of aggregation formation in bacterial colonies

    NASA Astrophysics Data System (ADS)

    Chavy-Waddy, Paul-Christopher; Kolokolnikov, Theodore

    2016-10-01

    We study pattern formation in a model of cyanobacteria motion recently proposed by Galante, Wisen, Bhaya and Levy. By taking a continuum limit of their model, we derive a novel fourth-order nonlinear parabolic PDE equation that governs the behaviour of the model. This PDE is {{u}t}=-{{u}xx}-{{u}xxxx}+α {{≤ft(\\frac{{{u}x}{{u}xx}}{u}\\right)}x} . We then derive the instability thresholds for the onset of pattern formation. We also compute analytically the spatial profiles of the steady state aggregation density. These profiles are shown to be of the form \\text{sec}{{\\text{h}}p} where the exponent p is related to the parameters of the model. Full numerical simulations give a favorable comparison between the continuum and the underlying discrete system, and show that the aggregation profiles are stable above the critical threshold.

  15. After Dark in the Antipodes: Pedagogy, Place and Queer Phenomenology

    ERIC Educational Resources Information Center

    Crowley, Vicki; Rasmussen, Mary Lou

    2010-01-01

    This paper pursues issues of pedagogy, place and queer phenomenology in the context of what might be meant by the term "after-queer" or "what falls outside queer" as we currently theorise, practice and locate queer. Inspired by Sara Ahmed's account of how bodies become oriented by the ways in which they take up time and space, this paper…

  16. Places to Go: Google's Search Results for "Net Generation"

    ERIC Educational Resources Information Center

    Downes, Stephen

    2007-01-01

    In his Places to Go column for a special issue on the Net Generation, Stephen Downes takes an unexpected trip--to Google. According to Downes, Google epitomizes the essence of the Net Generation. Infinitely searchable and adaptable, Google represents the spirit of a generation raised in the world of the Internet, a generation that adapts…

  17. Descending the Watershed: Rethinking the "Place" of Curriculum.

    ERIC Educational Resources Information Center

    Brody, Michael

    1997-01-01

    Employs a first-person phenomenological approach to describe an expedition for teachers from the uppermost beginning of a Northern Rocky Mountain watershed to its river output at the bottom. Focuses on the roles of people and place in the construction of new knowledge about the environment. Takes traditional curriculum theory a step beyond simple…

  18. Effects of Aggregation on Blood Sedimentation and Conductivity.

    PubMed

    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

  19. 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

  20. Taking human life.

    PubMed

    Brock, Dan W

    1985-07-01

    Alan Donagan's position regarding the morality of taking innocent human life, that it is impermissible regardless of the wishes of the victim, is criticized by Brock who argues for a rights-based alternative. His argument appeals to the nature of persons' actual interest in life and gives them an additional element of control which they lack if a nonwaivable moral duty not to kill prevails. The author rejects Donagan's view that stopping a life-sustaining treatment, even when a competent patient has consented, is morally wrong and that there is no moral difference between killing and allowing to die. A rights-based position permits stopping treatment of incompetent patients based on what the patient would have wanted or what is in his or her best interest, and allows the withholding of treatment from a terminally ill person, with the patient's consent and for a benevolent motive, to be evaluated as morally different from killing that patient.

  1. 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.

  2. Slow and fast capacitive process taking place at the ionic liquid/electrode interface.

    PubMed

    Roling, Bernhard; Drüschler, Marcel; Huber, Benediki

    2012-01-01

    Electrochemical impedance spectroscopy was used to characterise the interface between the ultrapure room temperature ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and a Au(111) working electrode at electrode potentials more positive than the open circuit potential (-0.14 V vs. Pt pseudo-reference). Plots of the potential-dependent data in the complex capacitance plane reveal the existence of a fast and a slow capacitive process. In order to derive the contribution of both processes to the overall capacitance, the complex capacitance data were fitted using an empirical Cole-Cole equation. The differential capacitance of the fast process is almost constant between -0.14 V and +0.2 V (vs. Pt pseudo-reference) and decreases at more positive potentials, while the differential capacitance of the slower process exhibits a maximum at +0.2 V. This maximum leads to a maximum in the overall differential capacitance. We attribute the slow process to charge redistributions in the innermost ion layer, which require an activation energy in excess of that for ion transport in the room temperature ionic liquid. The differential capacitance maximum of the slow process at +0.2 V is most likely caused by reorientations of the 1-butyl-1l-methylpyrrolidinium cations in the innermost layer with the positively charged ring moving away from the Au(111) surface and leaving behind voids which are then occupied by anions. In a recent Monte Carlo simulation by Federov, Georgi and Kornyshev (Electrochem. Commun. 2010, 12, 296), such a process was identified as the origin of a differential capacitance maximum in the anodic regime. Our results suggest that the time scales of capacitive processes at the ionic liquid/metal interface are an important piece of information and should be considered in more detail in future experimental and theoretical studies.

  3. To impose enhanced penalties for certain drug offense that take place on Federal property.

    THOMAS, 113th Congress

    Rep. Nunes, Devin [R-CA-22

    2013-06-05

    07/15/2013 Referred to the Subcommittee on Crime, Terrorism, Homeland Security, and Investigations. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

  4. Pairing K-12 Teachers with Geographic Researchers: Why It Should Take Place and How It Can.

    ERIC Educational Resources Information Center

    Orvis, Kenneth H.; Horn, Sally P.; Jumper, Sidney R.

    1999-01-01

    Contends that excitement can be infused into the K-12 geography curriculum by involving teachers in real research projects led by professional geographers. Describes a project where K-12 teachers and geographers participated in geography field research in the mountain highlands of the Valle Nuevo Scientific Reserve of the Dominican Republic. (CMK)

  5. When Private Schools Take Public Dollars: What's the Place of Accountability in School Voucher Programs?

    ERIC Educational Resources Information Center

    Finn, Chester E., Jr.; Hentges, Christina M.; Petrilli, Michael J.; Winkler, Amber M.

    2009-01-01

    Critics of school voucher programs argue that private schools that receive taxpayer dollars should be held accountable to the same standards as public schools. School choice supporters counter that private schools should be left alone to answer to the parents of their students. The authors advocate for a re-visit to the discussion of…

  6. Translational Science at the National Institute of Mental Health: Can Social Work Take Its Rightful Place?

    ERIC Educational Resources Information Center

    Brekke, John S.; Ell, Kathleen; Palinkas, Lawrence A.

    2007-01-01

    Several recent national reports have noted that there is a 20-year gap between knowledge generated from our best clinical research and the utilization of that knowledge in our health and mental health care sectors. One solution to this dilemma has been the emergence of translational science. Translational science has become a top priority of the…

  7. A Reaction that Takes Place in Beakers but not in Conical Flasks

    ERIC Educational Resources Information Center

    White, Colin; Ophardt, Charles

    2004-01-01

    Inductors are substances that undergo a reaction and in so doing markedly accelerate or induce a simultaneous reaction. An experiment showing a reaction involving the oxidation of iodide to iodine by chromium (VI) found to be slow in the absence of acid, but which proceeded rapidly when iron (II) was induced is demonstrated.

  8. Does Reflective Learning Take Place in Online MBA Introductory Quantitative Courses?

    ERIC Educational Resources Information Center

    Frank, Blake A.; Walsh, Robert J.

    2012-01-01

    Online education has grown dramatically over the past 15 years. At the university level, researchers have shown that online education has both its advantages--greater flexibility and access to student--and disadvantages--like disconnection with other students and faculty. Another possible drawback for the students enrolled in an online course is…

  9. In what time scale proton transfer takes place in a live CHO cell?

    NASA Astrophysics Data System (ADS)

    Mojumdar, Supratik Sen; Chowdhury, Rajdeep; Mandal, Amit Kumar; Bhattacharyya, Kankan

    2013-06-01

    Excited state proton transfer (ESPT) of pyranine (8-hydroxypyrene-1,3,6-trisulfonate, HPTS) in a live Chinese hamster ovary (CHO) cell is studied by time resolved confocal microscopy. The cytoplasm region of the cell is stained by a photoacid, HPTS (HA). The time constant of initial proton transfer (τPT) in the cell is found to be ˜10 times longer than that in bulk water, while the time constants of recombination (τrec) and dissociation (τdiss) in the cell are ˜3 times and ˜2 times longer, respectively. The slower rate of proton transfer (˜10 times) inside the CHO cell compared to that in bulk water is ascribed to slower solvation dynamics, lower availability of free water molecules, and disruption of hydrogen-bond network inside the cell. Translational and rotational diffusion of HPTS inside a single CHO cell have been investigated by fluorescence correlation spectroscopy (FCS) and picosecond anisotropy measurement, respectively. Both the translational and rotational diffusion slow down inside the live cell. FCS studies indicate that HPTS remains tightly bound to a macromolecule inside the cell.

  10. Look What I Am Doing: Does Observational Learning Take Place in Evocative Task-Sharing Situations?

    PubMed Central

    Ferraro, Luca; Iani, Cristina; Mariani, Michele; Nicoletti, Roberto; Gallese, Vittorio; Rubichi, Sandro

    2012-01-01

    Two experiments were conducted to investigate whether physical and observational practice in task-sharing entail comparable implicit motor learning. To this end, the social-transfer-of-learning (SToL) effect was assessed when both participants performed the joint practice task (Experiment 1 – complete task-sharing), or when one participant observed the other performing half of the practice task (Experiment 2 – evocative task-sharing). Since the inversion of the spatial relations between responding agent and stimulus position has been shown to prevent SToL, in the present study we assessed it in both complete and evocative task-sharing conditions either when spatial relations were kept constant or changed from the practice to the transfer session. The same pattern of results was found for both complete and evocative task-sharing, thus suggesting that implicit motor learning in evocative task-sharing is equivalent to that obtained in complete task-sharing. We conclude that this motor learning originates from the simulation of the complementary (rather than the imitative) action. PMID:22905256

  11. Where Does the Transformation of Precipitated Ceria Nanoparticles in Hydroponic Plants Take Place?

    PubMed

    Ma, Yuhui; Zhang, Peng; Zhang, Zhiyong; He, Xiao; Zhang, Junzhe; Ding, Yayun; Zhang, Jing; Zheng, Lirong; Guo, Zhi; Zhang, Lijuan; Chai, Zhifang; Zhao, Yuliang

    2015-09-01

    Cerium oxide nanoparticles (CeO2 NPs) have been found to be partly biotransformed from Ce(IV) to Ce(III) in plants, yet the transformation process and mechanism are not fully understood. Here, we try to clarify the specific site and necessary conditions for the transformation of precipitated CeO2 NPs in hydroponic cucumber plants. Three different treatment modes were adopted according to whether the NPs were incubated with roots all the time or not. Results showed that exposure modes significantly affect the translocation and transformation of CeO2 NPs. In the normal exposure mode, Ce was present as a Ce(IV) and Ce(III) mixture in the roots and shoots, and the proportion of Ce(III) in the shoots was enhanced obviously with the increase of exposure time. The results of short-time incubation and petiole exposure modes suggested that CeO2 NPs could not be reduced within a short incubation time (3 h) or be further reduced inside the plant tissues. It was deduced that root surfaces are the sites, and the physicochemical interaction between the NPs and root exudates at the nanobio interface is the necessary condition for the transformation of CeO2 NPs in plant systems. These results will contribute to understanding the transformation mechanism of CeO2 and other metal-based NPs and properly evaluate their ecological effects. PMID:26237071

  12. Where Does the Transformation of Precipitated Ceria Nanoparticles in Hydroponic Plants Take Place?

    PubMed

    Ma, Yuhui; Zhang, Peng; Zhang, Zhiyong; He, Xiao; Zhang, Junzhe; Ding, Yayun; Zhang, Jing; Zheng, Lirong; Guo, Zhi; Zhang, Lijuan; Chai, Zhifang; Zhao, Yuliang

    2015-09-01

    Cerium oxide nanoparticles (CeO2 NPs) have been found to be partly biotransformed from Ce(IV) to Ce(III) in plants, yet the transformation process and mechanism are not fully understood. Here, we try to clarify the specific site and necessary conditions for the transformation of precipitated CeO2 NPs in hydroponic cucumber plants. Three different treatment modes were adopted according to whether the NPs were incubated with roots all the time or not. Results showed that exposure modes significantly affect the translocation and transformation of CeO2 NPs. In the normal exposure mode, Ce was present as a Ce(IV) and Ce(III) mixture in the roots and shoots, and the proportion of Ce(III) in the shoots was enhanced obviously with the increase of exposure time. The results of short-time incubation and petiole exposure modes suggested that CeO2 NPs could not be reduced within a short incubation time (3 h) or be further reduced inside the plant tissues. It was deduced that root surfaces are the sites, and the physicochemical interaction between the NPs and root exudates at the nanobio interface is the necessary condition for the transformation of CeO2 NPs in plant systems. These results will contribute to understanding the transformation mechanism of CeO2 and other metal-based NPs and properly evaluate their ecological effects.

  13. When Private Schools Take Public Dollars: What's the Place of Accountability in School Voucher Programs?

    ERIC Educational Resources Information Center

    Finn, Chester E., Jr.; Hentges, Christina M.; Petrilli, Michael J.; Winkler, Amber M.

    2009-01-01

    Of all the arguments that critics of school voucher programs advance, the one that may resonate loudest with the public concerns school accountability. Opponents say it's not fair to hold public schools accountable for their results (under No Child Left Behind and similar systems) and then let private schools receive taxpayer dollars--however…

  14. Golgi and endoplasmic reticulum functions take place in different subcellular compartments of Entamoeba histolytica.

    PubMed

    Bredeston, Luis M; Caffaro, Carolina E; Samuelson, John; Hirschberg, Carlos B

    2005-09-16

    Entamoeba histolytica is a protozoan parasite that causes dysentery in developing countries of Africa, Asia, and Latin America. The lack of a defined Golgi apparatus in E. histolytica as well as in other protists led to the hypothesis that they had evolved prior to the acquisition of such organelle even though glycoproteins, glycolipids, and antigens have been detected, the latter of which react with antibodies against Golgi apparatus proteins of higher eukaryotes. We here provide direct evidence for Golgi apparatus-like functions in E. histolytica as well as for components of glycoprotein folding quality control. Using a combination of bioinformatic, cell biological, and biochemical approaches we have (a) cloned and expressed the E. histolytica UDP-galactose transporter in Saccharomyces cerevisiae; its K(m) for UDP-galactose is 2.9 microm; (b) characterized vesicles in an extract of the above protist, which transport UDP-galactose into their lumen with a K(m) of 2.7 microm;(c) detected galactosyltransferase activity(ies) in the lumen of the above vesicles with the K(m) for UDP-galactose, using endogenous acceptors, being 93 microm;(d) measured latent apyrase activities in the above vesicles, suggesting they are in the lumen; (e) characterized UDP-glucose transport activities in Golgi apparatus and endoplasmic reticulum-like vesicles with K(m)s for UDP-glucose of approximately 2-4 microm. Although the endoplasmic reticulum-like fraction showed UDP-glucose: glycoprotein glucosyltransferase activity, the Golgi apparatus-like fraction did not. This fraction contained other glucosyltransferases. Together, these studies demonstrate that E. histolytica has different vesicles that play a role in protein glycosylation and folding quality control, analogous to the above organellar functions of higher eukaryotes.

  15. Systemic analysis of desertification processes taking place in the Limpopo river basin

    NASA Astrophysics Data System (ADS)

    Messina, Mario; Attorre, Fabio; Vitale, Marcello

    2016-04-01

    Desertification and land degradation are phenomena that ranks among the greatest environmental challenges of our time. Desertification is a global issue, with serious implications worldwide for biodiversity, socio-economic stability and sustainable development. Biophysical indicators of land degradation and desertification, like Net Primary Productivity (NPP) and Total Ecosystem Respiration (Reco) were provided by remote sensing technology (MODIS). The study aims to evaluate the dynamical changes of NPP and Reco in the Limpopo river basin, a Southern African region that includes, Botswana, Mozambique, South Africa and Zimbabwe, during the time period 2001-2010. In particular, the relations between NPP, Reco, environmental, physiological and land use parameters have been widely investigated through the application of a new and powerful statistical classifier, the Random Forest Analysis (RFA), and a general non-linear model, the Response Surface Regression Model (GRM). RFA highlighted that Temperature is one of the most important predictors affecting NPP and Reco in the Limpopo river basin. Conversely, other environmental parameters like, Precipitation, Evapotranspiration and Vegetation cover rarely influence NPP and Reco. Our results provide information on desertification and land degradation phenomena and a first step for identifying practices to mitigate their negative impacts. However, it must be taken into account that NPP and Reco depend by a multitude of factors (e.g. human activities, socio-economic policies) and can vary in relation to spatial and temporal scale. In order to achieve a better understanding of land degradation and desertification processes, land use and socio-economic variables should be considered.

  16. Look what I am doing: does observational learning take place in evocative task-sharing situations?

    PubMed

    Ferraro, Luca; Iani, Cristina; Mariani, Michele; Nicoletti, Roberto; Gallese, Vittorio; Rubichi, Sandro

    2012-01-01

    Two experiments were conducted to investigate whether physical and observational practice in task-sharing entail comparable implicit motor learning. To this end, the social-transfer-of-learning (SToL) effect was assessed when both participants performed the joint practice task (Experiment 1--complete task-sharing), or when one participant observed the other performing half of the practice task (Experiment 2--evocative task-sharing). Since the inversion of the spatial relations between responding agent and stimulus position has been shown to prevent SToL, in the present study we assessed it in both complete and evocative task-sharing conditions either when spatial relations were kept constant or changed from the practice to the transfer session. The same pattern of results was found for both complete and evocative task-sharing, thus suggesting that implicit motor learning in evocative task-sharing is equivalent to that obtained in complete task-sharing. We conclude that this motor learning originates from the simulation of the complementary (rather than the imitative) action.

  17. 49 CFR 40.221 - Where does an alcohol test take place?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... alcohol testing site, you must ensure that it provides visual and aural privacy to the employee being tested, sufficient to prevent unauthorized persons from seeing or hearing test results. (d) If you are... privacy requirements of paragraph (c) is not readily available, this part allows a reasonable suspicion...

  18. Place prioritization for biodiversity content.

    PubMed

    Sarkar, Sahotra; Aggarwal, Anshu; Garson, Justin; Margules, Chris R; Zeidler, Juliane

    2002-07-01

    The prioritization of places on the basis of biodiversity content is part of any systematic biodiversity conservation planning process. The place prioritization procedure implemented in the ResNet software package is described. This procedure is primarily based on the principles of rarity and complementarity. Application of the procedure is demonstrated with two analyses, one data set consisting of the distributions of termite genera in Namibia, and the other consisting of the distributions of bird species in the Islas Malvinas/Falkland Islands. The attributes that data sets should have for the effective and reliable application of such procedures are discussed. The procedure used here is compared to some others that are also currently in use. PMID:12177533

  19. Detergent-mediated protein aggregation.

    PubMed

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

    2013-04-01

    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.

  20. 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.

  1. 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.

  2. Kinetic and hydrodynamic models of chemotactic aggregation

    NASA Astrophysics Data System (ADS)

    Chavanis, Pierre-Henri; Sire, Clément

    2007-10-01

    We derive general kinetic and hydrodynamic models of chemotactic aggregation that describe certain features of the morphogenesis of biological colonies (like bacteria, amoebae, endothelial cells or social insects). Starting from a stochastic model defined in terms of N coupled Langevin equations, we derive a nonlinear mean-field Fokker-Planck equation governing the evolution of the distribution function of the system in phase space. By taking the successive moments of this kinetic equation and using a local thermodynamic equilibrium condition, we derive a set of hydrodynamic equations involving a damping term. In the limit of small frictions, we obtain a hyperbolic model describing the formation of network patterns (filaments) and in the limit of strong frictions we obtain a parabolic model which is a generalization of the standard Keller-Segel model describing the formation of clusters (clumps). Our approach connects and generalizes several models introduced in the chemotactic literature. We discuss the analogy between bacterial colonies and self-gravitating systems and between the chemotactic collapse and the gravitational collapse (Jeans instability). We also show that the basic equations of chemotaxis are similar to nonlinear mean-field Fokker-Planck equations so that a notion of effective generalized thermodynamics can be developed.

  3. 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

  4. 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

  5. There's no place like home.

    PubMed

    Hudson, T

    1996-02-01

    When the school system in tiny Colby, Kans., signed onto a health plan that excluded the only hospital in the entire county, its citizens learned an important lesson. ¿If we're not working together,¿ says the hospital's administrator, ¿health plans and medical centers are going to come in here and take business away from us.¿ Here's what they learned about keeping rural health care rural.

  6. There's no place like home.

    PubMed

    Hudson, T

    1996-02-01

    When the school system in tiny Colby, Kans., signed onto a health plan that excluded the only hospital in the entire county, its citizens learned an important lesson. ¿If we're not working together,¿ says the hospital's administrator, ¿health plans and medical centers are going to come in here and take business away from us.¿ Here's what they learned about keeping rural health care rural. PMID:8616497

  7. 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

  8. 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.

  9. Aggregation server for grid-integrated vehicles

    DOEpatents

    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.

  10. Tubular aggregates: their association with myalgia.

    PubMed Central

    Niakan, E; Harati, Y; Danon, M J

    1985-01-01

    Three thousand consecutive muscle biopsies were reviewed for the presence of tubular aggregates and their association with clinical symptomatology. Tubular aggregates were detected in 19 patients (0.6%). Twelve of these nineteen patients had severe myalgia, and the most abundant tubular aggregates were found in biopsies of patients with myalgia. Seven patients had only myalgia as their clinical symptomatology with normal physical examination. An additional five patients with tubular aggregates and myalgia had concomitant amyotrophic lateral sclerosis (2) or neuropathy (3). The high incidence of myalgia associated with tubular aggregates in our patients and the fact that tubular aggregates originate from sarcoplasmic reticulum suggest a role played by this structure in the pathogenesis of myalgia. Images PMID:2995591

  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. Native metastable prefibrillar oligomers are the most neurotoxic species among amyloid aggregates.

    PubMed

    Diociaiuti, Marco; Macchia, Gianfranco; Paradisi, Silvia; Frank, Claudio; Camerini, Serena; Chistolini, Pietro; Gaudiano, Maria Cristina; Petrucci, Tamara Corinna; Malchiodi-Albedi, Fiorella

    2014-09-01

    Many proteins belonging to the amyloid family share the tendency to misfold and aggregate following common steps, and display similar neurotoxicity. In the aggregation pathway different kinds of species are formed, including several types of oligomers and eventually mature fibers. It is now suggested that the pathogenic aggregates are not the mature fibrils, but the intermediate, soluble oligomers. Many kinds of aggregates have been described to exist in a metastable state and in equilibrium with monomers. Up to now it is not clear whether a specific structure is at the basis of the neurotoxicity. Here we characterized, starting from the early aggregation stages, the oligomer populations formed by an amyloid protein, salmon calcitonin (sCT), chosen due to its very slow aggregation rate. To prepare different oligomer populations and characterize them by means of photoinduced cross-linking SDS-PAGE, Energy Filtered-Transmission Electron Microscopy (EF-TEM) and Circular Dichroism (CD) spectroscopy, we used Size Exclusion Chromatography (SEC), a technique that does not influence the aggregation process leaving the protein in the native state. Taking advantage of sCT low aggregation rate, we characterized the neurotoxic potential of the SEC-separated, non-crosslinked fractions in cultured primary hippocampal neurons, analyzing intracellular Ca(2+) influx and apoptotic trend. We provide evidence that native, globular, metastable, prefibrillar oligomers (dimers, trimers and tetramers) were the toxic species and that low concentrations of these aggregates in the population was sufficient to render the sample neurotoxic. Monomers and other kind of aggregates, such as annular or linear protofibers and mature fibers, were totally biologically inactive. PMID:24932517

  13. 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.

  14. 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

  15. An anthropologist in unexpected places

    PubMed Central

    Knutsen, Johan Henrik

    2014-01-01

    Much contemporary anthropology has turned away from exclusive focus on so-called “primitive” tribes in far-away places. The study of urban people has become more prominent, and some researchers have also turned their gaze towards marginalized minorities in their communities. Philippe Bourgois is an example of this. He is well known for studying crack dealers in East Harlem, New York ( In Search of Respect) and homeless heroin addicts in San Francisco (Righteous Dopefiend). Kula Kula was lucky enough to catch him in his office, and had a chat via skype. PMID:25436019

  16. Place of nutrition in yoga.

    PubMed

    Desai, B P

    1990-01-01

    Nutrition plays a very vital role in our life. Yoga and Ayurveda had laid down the foundations of dietetics. The valuable guidelines regarding various food articles and diet for Yoga Sadhaka, to achieve maximum benefits, are given in traditional yoga texts like Hatha Pradipika and Gheranda Samhitha. Now is the time to evaluate the place of nutrition in Yoga and to study how the dietetic principles in yoga will help to eradicate the national problem of Mal-nutrition and poverty which is the pressing need of the moment. PMID:22557690

  17. Multiway In-Place Merging

    NASA Astrophysics Data System (ADS)

    Geffert, Viliam; Gajdoš, Jozef

    We present an algorithm for asymptotically efficient k-way merging. Given an array A containing sorted subsequences A 1,...,A k of respective lengths n 1,...,n k , where sum_{i=1}kn_i = n, our algorithm merges A 1,...,A k in-place, into a single sorted sequence, performing lceil{lg k}rceil \\cdot n + o(n) element comparisons and 3·n + o(n) element moves. That is, our algorithm runs in linear time, with the number of moves independent of k, the number of input sequences.

  18. PLACE OF NUTRITION IN YOGA

    PubMed Central

    Desai, B.P.

    1990-01-01

    Nutrition plays a very vital role in our life. Yoga and Ayurveda had laid down the foundations of dietetics. The valuable guidelines regarding various food articles and diet for Yoga Sadhaka, to achieve maximum benefits, are given in traditional yoga texts like Hatha Pradipika and Gheranda Samhitha. Now is the time to evaluate the place of nutrition in Yoga and to study how the dietetic principles in yoga will help to eradicate the national problem of Mal-nutrition and poverty which is the pressing need of the moment. PMID:22557690

  19. A Place Pedagogy for "Global Contemporaneity"

    ERIC Educational Resources Information Center

    Somerville, Margaret J.

    2010-01-01

    Around the globe people are confronted daily with intransigent problems of space and place. Educators have historically called for place-based or place-conscious education to introduce pedagogies that will address such questions as how to develop sustainable communities and places. These calls for place-conscious education have included liberal…

  20. Microbial aggregates in anaerobic wastewater treatment.

    PubMed

    Kosaric, N; Blaszczyk, R

    1990-01-01

    The phenomenon aggregation of anaerobic bacteria gives an opportunity to speed up the digestion rate during methanogenesis. The aggregates are mainly composed of methanogenic bacteria which convert acetate and H2/CO2 into methane. Other bacteria are also included in the aggregates but their concentration is rather small. The aggregates may also be formed during acetogenesis or even hydrolysis but such aggregates are not stable and disrupt quickly when not fed. A two stage process seems to be suitable when high concentrated solid waste must be treated. Special conditions are necessary to promote aggregate formation from methanogenic bacteria but aggregates once formed are stable without feeding even for a few years. The structure, texture and activity of bacterial aggregates depend on several parameters: (1)--temperature and pH, (2)--wastewater composition and (3)--hydrodynamic conditions within the reactor. The common influence of all these parameters is still rather unknown but some recommendations may be given. Temperature and pH should be maintained in the range which is optimal for methanogenic bacteria e.g. a temperature between 32 and 50 degrees C and a value pH between 6.5 and 7.5. Wastewaters should contain soluble wastes and the specific loading rate should be around one kgCOD(kgVSS)-1 d-1. The concentration of the elements influences aggregate composition and probably structure and texture. At high calcium concentration a change in the colour of the granules has been observed. Research is necessary to investigate the influence of other elements and organic toxicants on maintenance of the aggregates. Hydrodynamic conditions seem to influence the stability of the granules over long time periods. At low liquid stream rates, aggregates may starve and lysis within the aggregates is possible which results in hollowing of aggregates and their floating. At high liquid stream rates the aggregates may be disrupted and washed out of the reactor as a flocculent

  1. 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

  2. Immunogenicity of therapeutic proteins: influence of aggregation.

    PubMed

    Ratanji, Kirsty D; 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.

  3. 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.

  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. 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.

  6. 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.

  7. 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.

  8. Emerin expression in tubular aggregates.

    PubMed

    Manta, Panagiota; Terzis, Gerasimos; Papadimitriou, Constantinos; Kontou, Chrysanthi; Vassilopoulos, Demetris

    2004-06-01

    Emerin is an inner nuclear membrane protein that is mutated or not expressed in patients with X-linked Emery-Dreifuss muscular dystrophy (X-EDMD/EMD). Cytoplasmic localization of emerin in cultured cells or tissues has been reported, although this remains a controversial issue. Tubular aggregates (TAs) are pathological structures seen in the sarcoplasm of human skeletal muscle fibers in various disorders. The TAs derive from the sarcoplasmic reticulum (SR) and represent, probably, an adaptive response of the SR to various insults to the muscle fibers. In the present study, we present immunohistochemical evidence of emerin expression in TAs. Muscle biopsies with tubular aggregates from four male, unrelated patients were studied. The percentage of muscle fibers containing TAs varied between 5 and 20%. Routine histochemistry revealed intense reaction of TAs with NADH-TR, AMPDA, and NSE, but not with COX, SDH, myosin ATPase (pH 9.4, 4.3, 4.6), PAS, and Oil red O staining. Immunohistochemical study revealed strong immunostaining of TAs with antibodies against emerin and 7 SERCA2-ATPase. Immunostaining of TAs was also seen with antibodies against heat shock protein and dysferlin, but not with antibodies to lamin A, dystrophin, adhalin, beta, gamma, delta sarcoglycans, and merosin. These results suggest that emerin, an inner nuclear membrane protein, is present at the TAs. The interpretation and significance of this finding is discussed in relation to experimental data suggesting that normal emerin localization at the inner nuclear membrane depends on lamin A and mutations in the N-terminal domain of emerin cause mislocalization of the protein to the sarcoplasmic membranes.

  9. 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

  10. The infrared spectral transmittance of Aspergillus niger spore aggregated particle swarm

    NASA Astrophysics Data System (ADS)

    Zhao, Xinying; Hu, Yihua; Gu, Youlin; Li, Le

    2015-10-01

    Microorganism aggregated particle swarm, which is quite an important composition of complex media environment, can be developed as a new kind of infrared functional materials. Current researches mainly focus on the optical properties of single microorganism particle. As for the swarm, especially the microorganism aggregated particle swarm, a more accurate simulation model should be proposed to calculate its extinction effect. At the same time, certain parameters deserve to be discussed, which helps to better develop the microorganism aggregated particle swarm as a new kind of infrared functional materials. In this paper, take Aspergillus Niger spore as an example. On the one hand, a new calculation model is established. Firstly, the cluster-cluster aggregation (CCA) model is used to simulate the structure of Aspergillus Niger spore aggregated particle. Secondly, the single scattering extinction parameters for Aspergillus Niger spore aggregated particle are calculated by using the discrete dipole approximation (DDA) method. Thirdly, the transmittance of Aspergillus Niger spore aggregated particle swarm is simulated by using Monte Carlo method. On the other hand, based on the model proposed above, what influences can wavelength causes has been studied, including the spectral distribution of scattering intensity of Aspergillus Niger spore aggregated particle and the infrared spectral transmittance of the aggregated particle swarm within the range of 8~14μm incident infrared wavelengths. Numerical results indicate that the scattering intensity of Aspergillus Niger spore aggregated particle reduces with the increase of incident wavelengths at each scattering angle. Scattering energy mainly concentrates on the scattering angle between 0~40°, forward scattering has an obvious effect. In addition, the infrared transmittance of Aspergillus Niger spore aggregated particle swarm goes up with the increase of incident wavelengths. However, some turning points of the trend

  11. Simple off-lattice model to study the folding and aggregation of peptides

    NASA Astrophysics Data System (ADS)

    Combe, Nicolas; Frenkel, Daan

    We present a numerical study of a new protein model. This off-lattice model takes into account both the hydrogen bonds and the amino-acid interactions. It reproduces the folding of a small protein (peptide): morphological analysis of the conformations at low temperature shows two well-known substructures α-helix and β-sheet depending on the chosen sequence. The folding pathway in the scope of this model is studied through a free-energy analysis. We then study the aggregation of proteins. Proteins in the aggregate are mainly bound via hydrogen bonds. Performing a free-energy analysis we show that the addition of a peptide to such an aggregate is not favourable. We qualitatively reproduce the abnormal aggregation of proteins in prion diseases.

  12. Protein aggregation activates erratic stress response in dietary restricted yeast cells

    PubMed Central

    Bhadra, Ankan Kumar; Das, Eshita; Roy, Ipsita

    2016-01-01

    Chronic stress and prolonged activation of defence pathways have deleterious consequences for the cell. Dietary restriction is believed to be beneficial as it induces the cellular stress response machinery. We report here that although the phenomenon is beneficial in a wild-type cell, dietary restriction leads to an inconsistent response in a cell that is already under proteotoxicity-induced stress. Using a yeast model of Huntington’s disease, we show that contrary to expectation, aggregation of mutant huntingtin is exacerbated and activation of the unfolded protein response pathway is dampened under dietary restriction. Global proteomic analysis shows that when exposed to a single stress, either protein aggregation or dietary restriction, the expression of foldases like peptidyl-prolyl isomerase, is strongly upregulated. However, under combinatorial stress, this lead is lost, which results in enhanced protein aggregation and reduced cell survival. Successful designing of aggregation-targeted therapeutics will need to take additional stressors into account. PMID:27633120

  13. Protein aggregation activates erratic stress response in dietary restricted yeast cells.

    PubMed

    Bhadra, Ankan Kumar; Das, Eshita; Roy, Ipsita

    2016-01-01

    Chronic stress and prolonged activation of defence pathways have deleterious consequences for the cell. Dietary restriction is believed to be beneficial as it induces the cellular stress response machinery. We report here that although the phenomenon is beneficial in a wild-type cell, dietary restriction leads to an inconsistent response in a cell that is already under proteotoxicity-induced stress. Using a yeast model of Huntington's disease, we show that contrary to expectation, aggregation of mutant huntingtin is exacerbated and activation of the unfolded protein response pathway is dampened under dietary restriction. Global proteomic analysis shows that when exposed to a single stress, either protein aggregation or dietary restriction, the expression of foldases like peptidyl-prolyl isomerase, is strongly upregulated. However, under combinatorial stress, this lead is lost, which results in enhanced protein aggregation and reduced cell survival. Successful designing of aggregation-targeted therapeutics will need to take additional stressors into account. PMID:27633120

  14. Taking Care of Your Vision

    MedlinePlus

    ... a Friend Who Cuts? Taking Care of Your Vision KidsHealth > For Teens > Taking Care of Your Vision ... are important parts of keeping your peepers perfect. Vision Basics One of the best things you can ...

  15. Flow Partitioning in Fully Saturated Soil Aggregates

    SciTech Connect

    Yang, Xiaofan; Richmond, Marshall C.; Scheibe, Timothy D.; Perkins, William A.; Resat, Haluk

    2014-03-30

    Microbes play an important role in facilitating organic matter decomposition in soils, which is a major component of the global carbon cycle. Microbial dynamics are intimately coupled to environmental transport processes, which control access to labile organic matter and other nutrients that are needed for the growth and maintenance of microorganisms. Transport of soluble nutrients in the soil system is arguably most strongly impacted by preferential flow pathways in the soil. Since the physical structure of soils can be characterized as being formed from constituent micro aggregates which contain internal porosity, one pressing question is the partitioning of the flow among the “inter-aggregate” and “intra-aggregate” pores and how this may impact overall solute transport within heterogeneous soil structures. The answer to this question is particularly important in evaluating assumptions to be used in developing upscaled simulations based on highly-resolved mechanistic models. We constructed a number of diverse multi-aggregate structures with different packing ratios by stacking micro-aggregates containing internal pores and varying the size and shape of inter-aggregate pore spacing between them. We then performed pore-scale flow simulations using computational fluid dynamics methods to determine the flow patterns in these aggregate-of-aggregates structures and computed the partitioning of the flow through intra- and inter-aggregate pores as a function of the spacing between the aggregates. The results of these numerical experiments demonstrate that soluble nutrients are largely transported via flows through inter-aggregate pores. Although this result is consistent with intuition, we have also been able to quantify the relative flow capacity of the two domains under various conditions. For example, in our simulations, the flow capacity through the aggregates (intra-aggregate flow) was less than 2% of the total flow when the spacing between the aggregates

  16. Acetal phosphatidic acids: novel platelet aggregating agents.

    PubMed

    Brammer, J P; Maguire, M H; Walaszek, E J; Wiley, R A

    1983-05-01

    1 Palmitaldehyde, olealdehyde and linolealdehyde acetal phosphatidic acids induced rapid shape change and dose-dependent biphasic aggregation of human platelets in platelet-rich plasma; aggregation was reversible at low doses and irreversible at high doses of the acetal phosphatidic acids. The palmitaldehyde congener elicited monophasic dose-dependent aggregation of sheep platelets in platelet-rich plasma.2 The threshold concentration for palmitaldehyde acetal phosphatidic acid (PGAP)-induced platelet aggregation was 2.5-5 muM for human platelets and 0.25-0.5 muM for sheep platelets. PGAP was 4-5 times as potent versus human platelets as the olealdehyde and linolealdehyde acetal phosphatidic acids, which were equipotent.3 PGAP-induced irreversible aggregation of [(14)C]-5-hydroxytryptamine ([(14)C]-5-HT)-labelled human platelets in platelet-rich plasma was accompanied by release of 44.0+/-2.4% (s.e.) of the platelet [(14)C]-5-HT; reversible aggregation was not associated with release. In contrast, PGAP-induced release of [(14)C]-5-HT-labelled sheep platelets was dose-dependent.4 The adenosine diphosphate (ADP) antagonist, 2-methylthio-AMP, and the cyclo-oxygenase inhibitor, aspirin, abolished PGAP-induced second phase aggregation and release in human platelets but did not affect the first, reversible, phase of aggregation. Both the first and second phases of PGAP-induced aggregation were abolished by chlorpromazine, by the phospholipase A(2) inhibitor, mepacrine, and by nmolar concentrations of prostaglandin E(1) (PGE(1)); these agents abolished the second, but not the first phase of ADP-induced aggregation.5 The related phospholipids, lecithin, lysolecithin and phosphatidic acid, at <100 muM, neither induced aggregation of human platelets in platelet-rich plasma, nor modified PGAP-induced aggregation; 1-palmityl lysophosphatidic acid elicited aggregation of human platelets at a threshold concentration of 100 muM.6 It is concluded that the acetal phosphatidic acids

  17. Succession of Protists on Estuarine Aggregates.

    PubMed

    Wörner; Zimmerman-Timm; Kausch

    2000-08-01

    Colonization by and succession of bacteria and bacterivorous protists on laboratory-made aggregates were determined over a period of 14 days during winter and spring in 1997. Aggregates were generated from natural water from the limnetic zone of the Elbe Estuary using a tilting tube roller system. Within 1 h after the beginning of the experiments, macroaggregates started to form. Aggregates reached a maximum size of 1 mm with a tendency toward large sizes at the end of the experiment after the 10th day. On the first day, high bacterial densities of more than 10(9) cells ml(-1) were detected within the aggregates. The abundances of flagellates and ciliates within aggregates were also two or three orders of magnitude higher than in the surrounding water. Densities of aggregate associated organisms are comparable to those occuring in sediments. The first protistan colonizers on the aggregates were small heterotrophic flagellates, such as choanoflagellates and small euglenids. Later, beginning on the 4th day, small sarcodines and ciliates became abundant. The most abundant ciliates associated with aggregates were small species of the Hypotrichia, Cyrtophorida, and Hymenostomata. After 9 days, large omnivorous and carnivorous ciliates, such as large members of the Hypotrichia and the Pleurostomatida, occurred. In spring, large heterotrophic flagellates and amebae also appeared at this time. These findings indicated the existence of a succession of protists on newly formed aggregates and a microbial food net within the aggregates based on bacterial production. Additionally, most of the species observed during this study were adapted for living on surfaces. In natural environments they are more common in benthic than in pelagic environments. For them, aggregates are havens in the water column comparable to sediment communities.

  18. Preformed Seeds Modulate Native Insulin Aggregation Kinetics.

    PubMed

    Dutta, Colina; Yang, Mu; Long, Fei; Shahbazian-Yassar, Reza; Tiwari, Ashutosh

    2015-12-10

    Insulin aggregates under storage conditions via disulfide interchange reaction. It is also known to form aggregates at the site of repeated injections in diabetes patients, leading to injection amyloidosis. This has fueled research in pharmaceutical and biotechnology industry as well as in academia to understand factors that modulate insulin stability and aggregation. The main aim of this study is to understand the factors that modulate aggregation propensity of insulin under conditions close to physiological and measure effect of "seeds" on aggregation kinetics. We explored the aggregation kinetics of insulin at pH 7.2 and 37 °C in the presence of disulfide-reducing agent dithiothreitol (DTT), using spectroscopy (UV-visible, fluorescence, and Fourier transform infrared spectroscopy) and microscopy (scanning electron microscopy, atomic force microscopy) techniques. We prepared insulin "seeds" by incubating disulfide-reduced insulin at pH 7.2 and 37 °C for varying lengths of time (10 min to 12 h). These seeds were added to the native protein and nucleation-dependent aggregation kinetics was measured. Aggregation kinetics was fastest in the presence of 10 min seeds suggesting they were nascent. Interestingly, intermediate seeds (30 min to 4 h incubation) resulted in formation of transient fibrils in 4 h that converted to amorphous aggregates upon longer incubation of 24 h. Overall, the results show that insulin under disulfide reducing conditions at pH and temperature close to physiological favors amorphous aggregate formation and seed "maturity" plays an important role in nucleation dependent aggregation kinetics.

  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. Complex Kepler Orbits and Particle Aggregation in Charged Microscopic Grains

    NASA Astrophysics Data System (ADS)

    Lee, Victor; Waitukaitis, Scott; Miskin, Marc; Jaeger, Heinrich

    2015-03-01

    Kepler orbits are usually associated with the motion of astronomical objects such as planets or comets. Here we observe such orbits at the microscale in a system of charged, insulating grains. By letting the grains fall freely under vacuum, we eliminate the effects of air drag and gravity, and by imaging them with a co-falling high-speed camera we track the relative positions of individual particles with high spatial and temporal precision. This makes it possible to investigate the behaviors caused by the combination of long-range electrostatic interactions and short-range, dissipative, contact interactions in unprecedented detail. We make the first direct observations of microscopic elliptical and hyperbolic Kepler orbits, collide-and-capture events between pairs of charged grains, and particle-by-particle aggregation into larger clusters. Our findings provide experimental evidence for electrostatic mechanisms that have been suspected, but not previously observed at the single-event level, as driving the early stages of particle aggregation in systems ranging from fluidized particle bed reactors to interstellar protoplanetary disks. Furthermore, since particles of different net charge and size are seen to aggregate into characteristic spatial configurations, our results suggest new possibilities for the formation of charge-stabilized ``granular molecules''. We can reproduce the observed molecule configurations by taking many-body, dielectric polarization effects into account.

  1. 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

  2. 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 §...

  3. 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 §...

  4. 48 CFR 514.270 - Aggregate awards.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Aggregate awards. 514.270 Section 514.270 Federal Acquisition Regulations System GENERAL SERVICES ADMINISTRATION CONTRACTING METHODS AND CONTRACT TYPES SEALED BIDDING Solicitation of Bids 514.270 Aggregate awards....

  5. 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.

  6. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification § 58.32... the total project must be listed and described by the responsible entity in the environmental review... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Project aggregation. 58.32...

  7. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification § 58.32... the total project must be listed and described by the responsible entity in the environmental review... 24 Housing and Urban Development 1 2011-04-01 2011-04-01 false Project aggregation. 58.32...

  8. 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…

  9. 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…

  10. 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...

  11. 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...

  12. 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...

  13. 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 ...

  14. Estimating the Reliability of Aggregated and Within-Person Centered Scores in Ecological Momentary Assessment

    ERIC Educational Resources Information Center

    Huang, Po-Hsien; Weng, Li-Jen

    2012-01-01

    A procedure for estimating the reliability of test scores in the context of ecological momentary assessment (EMA) was proposed to take into account the characteristics of EMA measures. Two commonly used test scores in EMA were considered: the aggregated score (AGGS) and the within-person centered score (WPCS). Conceptually, AGGS and WPCS represent…

  15. 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

  16. 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.

  17. 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

  18. CHARGING OF AGGREGATE GRAINS IN ASTROPHYSICAL ENVIRONMENTS

    SciTech Connect

    Ma, Qianyu; Matthews, Lorin S.; Hyde, Truell W.; Land, Victor

    2013-02-15

    The charging of dust grains in astrophysical environments has been investigated with the assumption that these grains are homogeneous spheres. However, there is evidence which suggests that many grains in astrophysical environments are irregularly shaped aggregates. Recent studies have shown that aggregates acquire higher charge-to-mass ratios due to their complex structures, which in turn may alter their subsequent dynamics and evolution. In this paper, the charging of aggregates is examined including secondary electron emission and photoemission in addition to primary plasma currents. The results show that the equilibrium charge on aggregates can differ markedly from spherical grains with the same mass, but that the charge can be estimated for a given environment based on structural characteristics of the grain. The 'small particle effect' due to secondary electron emission is also important for de terming the charge of micron-sized aggregates consisting of nano-sized particles.

  19. 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

  20. 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

  1. 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

  2. Reconsidering the mechanism of polyglutamine peptide aggregation.

    PubMed

    Lee, Christine C; Walters, Robert H; Murphy, Regina M

    2007-11-01

    There are at least nine neurodegenerative diseases associated with proteins that contain an unusually expanded polyglutamine domain, the best known of which is Huntington's disease. In all of these diseases, the mutant protein aggregates into neuronal inclusions; it is generally, although not universally, believed that protein aggregation is an underlying cause of the observed neuronal degeneration. In an effort to examine the role of polyglutamine in facilitating protein aggregation, investigators have used synthetic polyglutamine peptides as model systems. Analysis of kinetic data led to the conclusions that aggregation follows a simple nucleation-elongation mechanism characterized by a significant lag time, during which the peptide is monomeric, and that the nucleus is a monomer in a thermodynamically unfavorable conformation [Chen, S. M., et al. (2002) Proc. Natl. Acad. Sci. U.S.A. 99, 11884-11889]. We re-examined this hypothesis by measuring the aggregation kinetics of the polyglutamine peptide K2Q23K2, using sedimentation, static and dynamic light scattering, and size exclusion chromatography. Our data show that during the lag time in sedimentation kinetics, there is substantial organization of the peptide into soluble linear aggregates. These aggregates have no regular secondary structure as measured by circular dichroism but have particle dimensions and morphologies similar to those of mature insoluble aggregates. The soluble aggregates constitute approximately 30% of the total peptide mass, form rapidly, and continue to grow over a period of hours to days, eventually precipitating. Once insoluble aggregates form, loss of monomer from the solution phase continues. Our data support an assembly mechanism for polyglutamine peptide more complex than that previously proposed.

  3. 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

  4. Sans study of asphaltene aggregation

    SciTech Connect

    Overfield, R.E.; Sheu, E.Y.; Sinha, S.K.; Liang, K.S. )

    1988-06-01

    The colloidal properties of asphaltenes have long been recognized from peculiarities in their solubility and colligative properties. A layered micellar model or asphaltenes was proposed by others in which a highly condensed alkyl aromatic formed the central part, and molecules of decreasingly aromatic character (resins) clustered around them. Numerous studies, based on a variety of techniques such as ultracentrifugation and electron microscopy indicated a particulate nature for asphaltenes with size 20-40 A diameter. Others have proposed a refined model based on x-ray diffraction and small angle scattering. In this model, interactions between flat sheets of condensed aromatic rings form the central ''crystallite'' part of a spherical particle with the outer part being comprised of the aliphatic positions of the same molecules. These particles are bunched together with some degree of entanglement into ''micelles''. Concentration and solvent dependent radii of gyration, ranging from 30-50 A were reported. The aggregation creates a good deal of uncertainty as to the true molecular size or weight of asphaltenes. Neutron scattering offers novel contrast relative to light scattering (refractive index) and x-ray scattering (electron density). This is because the scattering length of proton is negative, whereas that from deuterium and other nuclei such as C, S, O, and N are positive. Thus by replacing hydrogen with deuterium in either the solvent or the scatterer the contrast can be varied, and different parts of the molecule can be highlighted.

  5. 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

  6. In-place coating method

    SciTech Connect

    Not Available

    1986-07-01

    Fuel pipelines at military aviation facilities are critical to mission accomplishment. Clean aviation fuel, free from contamination, is a must for flight safety. Internal corrosion and pipeline leaks cannot be tolerated. Repairs to, and replacement of, pipelines that are often buried under thick, reinforced concrete, can be difficult, expensive, and time consuming. Excavations to uncover such lines can totally disrupt flight operations. An in-place pipeline internal rehabilitation service has been utilized recently to clean and internally coat three major military jet fuel pipelines serving military airfields in New Hampshire, North Carolina, and Florida. The rehabilitation projects were accomplished by UCISCO (Union Carbide Industrial Services Co.) with little or no disruptive excavation. The total process involves, first, thorough internal cleaning of the pipe using the SANDJET pipeline cleaning service to completely remove deposits and corrosion down to bare white metal and leave a clean blasted surface in a dry, inert nitrogen atmosphere - conditions ideal for application of a polyamide epoxy coating material. The epoxy coating provides a smooth, continuous inner surface that is free of holidays and helps improve the flow efficiency of the line as well as protecting products from possible corrosion contamination.

  7. The astrophysics of crowded places.

    PubMed

    Davies, Melvyn

    2002-12-15

    Today the Sun is in a relatively uncrowded place. The distance between it and the nearest other star is relatively large (about 200,000 times the Earth-Sun distance!). This is beneficial to life on Earth; a close encounter with another star is extremely unlikely. Such encounters would either remove the Earth from its orbit around the Sun or leave it on an eccentric orbit similar to a comet's. But the Sun was not formed in isolation. It was born within a more-crowded cluster of perhaps a few hundred stars. As the surrounding gas evaporated away, the cluster itself evaporated too, dispersing its stars into the Galaxy. Virtually all stars in the Galaxy share this history, and here I will describe the role of 'clusterness' in a star's life. Stars are often formed in larger stellar clusters (known as open and globular clusters), some of which are still around today. I will focus on stars in globular clusters and describe how the interactions between stars in these clusters may explain the zoo of stellar exotica which have recently been observed with instruments such as the Hubble Space Telescope and the X-ray telescopes XMM-Newton and Chandra. In recent years, myriad planets orbiting stars other than the Sun--the so-called 'extrasolar' planets--have been discovered. I will describe how a crowded environment will affect such planetary systems and may in fact explain some of their mysterious properties.

  8. The astrophysics of crowded places.

    PubMed

    Davies, Melvyn

    2002-12-15

    Today the Sun is in a relatively uncrowded place. The distance between it and the nearest other star is relatively large (about 200,000 times the Earth-Sun distance!). This is beneficial to life on Earth; a close encounter with another star is extremely unlikely. Such encounters would either remove the Earth from its orbit around the Sun or leave it on an eccentric orbit similar to a comet's. But the Sun was not formed in isolation. It was born within a more-crowded cluster of perhaps a few hundred stars. As the surrounding gas evaporated away, the cluster itself evaporated too, dispersing its stars into the Galaxy. Virtually all stars in the Galaxy share this history, and here I will describe the role of 'clusterness' in a star's life. Stars are often formed in larger stellar clusters (known as open and globular clusters), some of which are still around today. I will focus on stars in globular clusters and describe how the interactions between stars in these clusters may explain the zoo of stellar exotica which have recently been observed with instruments such as the Hubble Space Telescope and the X-ray telescopes XMM-Newton and Chandra. In recent years, myriad planets orbiting stars other than the Sun--the so-called 'extrasolar' planets--have been discovered. I will describe how a crowded environment will affect such planetary systems and may in fact explain some of their mysterious properties. PMID:12626265

  9. 75 FR 8652 - Incidental Takes of Marine Mammals During Specified Activities; Marine Geophysical Survey in the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-25

    ....S. The survey will take place in the Exclusive Economic Zone (EEZ) of the U.S. in water depths... transect lines within the CNMI (see Figure 1 of L-DEO's application). The survey will take place in water... varies with water depth. The pulse interval is 1 s, but a common mode of operation is to broadcast...

  10. 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.

  11. Efficient clustering aggregation based on data fragments.

    PubMed

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

    2012-06-01

    Clustering aggregation, known as clustering ensembles, has emerged as a powerful technique for combining different clustering results to obtain a single better clustering. Existing clustering aggregation algorithms are applied directly to data points, in what is referred to as the point-based approach. The algorithms are inefficient if the number of data points is large. We define an efficient approach for clustering aggregation based on data fragments. In this fragment-based approach, a data fragment is any subset of the data that is not split by any of the clustering results. To establish the theoretical bases of the proposed approach, we prove that clustering aggregation can be performed directly on data fragments under two widely used goodness measures for clustering aggregation taken from the literature. Three new clustering aggregation algorithms are described. The experimental results obtained using several public data sets show that the new algorithms have lower computational complexity than three well-known existing point-based clustering aggregation algorithms (Agglomerative, Furthest, and LocalSearch); nevertheless, the new algorithms do not sacrifice the accuracy. PMID:22334025

  12. Place-Identity in a School Setting: Effects of the Place Image

    ERIC Educational Resources Information Center

    Marcouyeux, Aurore; Fleury-Bahi, Ghozlane

    2011-01-01

    Studies on place identity show positive relationships between the evaluation of a place and mechanisms involved in place identification. However, individuals also identify with places of low social prestige (places that bear a negative social image). Few authors investigate the nature of place identity processes in this case. The goal of this…

  13. Oh, the Places They Went: SBOs Share Their Career Paths

    ERIC Educational Resources Information Center

    George, Patricia

    2013-01-01

    "Oh the Places You'll Go!" That Dr. Seuss book is a standard gift for graduates as they are sent out into the world-whether it's off to college or into the world of work. "You can steer yourself any direction you choose." What direction did school business officials take to get where they are today? The most recent…

  14. Seasonal variability of soil aggregate stability

    NASA Astrophysics Data System (ADS)

    Rohoskova, M.; Kodesova, R.; Jirku, V.; Zigova, A.; Kozak, J.

    2009-04-01

    Seasonal variability of soil properties measured in surface horizons of three soil types (Haplic Luvisol, Greyic Phaeozem, Haplic Cambisol) was studied in years 2007 and 2008. Undisturbed and disturbed soil samples were taken every month to evaluate field water content, bulk density, porosity, ration of gravitational and capillary pores, pHKCl and pHH2O, organic matter content and its quality, aggregate stability using WSA index. In addition, micromorphological features of soil aggregates were studied in thin soil sections that were made from undisturbed large soil aggregates. Results showed that soil aggregate stability depended on stage of the root zone development, soil management and climatic conditions. Larger aggregate stabilities and also larger ranges of measure values were obtained in the year 2007 then those measured in 2008. This was probably caused by lower precipitations and consequently lower soil water contents observed in 2007 than those measured in 2008. The highest aggregate stability was measured at the end of April in the years 2007 and 2008 in Haplic Luvisol and Greyic Phaeozem, and at the end of June in the year 2007 and at the beginning of June in 2008 in Haplic Cambisol. In all cases aggregate stability increased during the root growth and then gradually decreased due to summer rainfall events. Aggregate stability reflected aggregate structure and soil pore system development, which was documented on micromorphological images and evaluated using the ration of gravitational and capillary pores measured on the undisturbed sol samples. Acknowledgement: Authors acknowledge the financial support of the Grant Agency of the Czech Republic grant No. 526/08/0434, and the Ministry of Education, Youth and Sports grant No. MSM 6046070901.

  15. Molecular Mechanism of the Early Stage of Amyloidogenic Hexapeptides (NFGAIL) Aggregation

    NASA Astrophysics Data System (ADS)

    Shi, Bi-Yun; Zhou, Bo; Cai, Zhuo-Wei; Xiu, Peng; Yang, Zai-Xing

    2013-10-01

    Peptides/proteins aggregation can give rise to pathological conditions of many human diseases. Small partially ordered oligomers formed in the early stage of aggregation, rather than mature fibrils, are thought to be the main toxicity agent for the living cell. Thus, understanding the pathway and the underlying physical mechanism in the early stage of aggregation is very important for prevention and treatment of these protein functional diseases. Herein we use all-atom molecular dynamics simulations to study the aggregation of four NFGAIL hexapeptides (NFGAIL peptide is a core segment of human islet amyloid polypeptide and exhibits similar aggregation kinetics as the full-length polypeptide). We observe that the peptide monomers in water mainly adopt non-structural coil configurations; the four peptides which are randomly placed in water aggregate spontaneously to partially ordered oligomer (β-sheets) through dimerization or trimerization, with the dimerization predominated. Both parallel and anti-parallel β-sheets are observed. The hydrophobic interactions drive the initial peptides associations, and the subsequent conformational fluctuations promote the formation of more hydrogen bonds between the dangling hydrogen sites in the main chains of peptides.

  16. Mucin aggregation from a rod-like meso-scale model

    NASA Astrophysics Data System (ADS)

    Moreno, Nicolas; Perilla, Jairo E.; Colina, Coray M.; Lísal, Martin

    2015-05-01

    Dissipative particle dynamics, a meso-scale particle-based model, was used to study the aggregation of mucins in aqueous solutions. Concentration, strength of the mucin-water interactions, as well as the effects of size, shape, and composition of the model molecules were studied. Model proteins were represented as rod-like objects formed by coarse-grained beads. In the first model, only one type of beads formed the mucin. It was found that all the surfaces were available to form aggregates and the conformation of the aggregates was a function of the strength of the mucin-water interaction. With this model, the number of aggregates was unaffected by the initial position of the mucins in the simulation box, except for the lowest mucin concentration. In a more refined mucin model, two kinds of beads were used in the molecule in order to represent the existence of cysteine-like terminal groups in the actual molecule. With this new scheme, aggregation took place by the interaction of the terminal groups between model molecules. The kinetic analysis of the evolution of the number of aggregates with time was also studied for both mucin models.

  17. Symmetries and pattern formation in hyperbolic versus parabolic models of self-organised aggregation.

    PubMed

    Buono, Pietro-Luciano; Eftimie, Raluca

    2015-10-01

    The study of self-organised collective animal behaviour, such as swarms of insects or schools of fish, has become over the last decade a very active research area in mathematical biology. Parabolic and hyperbolic models have been used intensively to describe the formation and movement of various aggregative behaviours. While both types of models can exhibit aggregation-type patterns, studies on hyperbolic models suggest that these models can display a larger variety of spatial and spatio-temporal patterns compared to their parabolic counterparts. Here we use stability, symmetry and bifurcation theory to investigate this observation more rigorously, an approach not attempted before to compare and contrast aggregation patterns in models for collective animal behaviors. To this end, we consider a class of nonlocal hyperbolic models for self-organised aggregations that incorporate various inter-individual communication mechanisms, and take the formal parabolic limit to transform them into nonlocal parabolic models. We then discuss the symmetry of these nonlocal hyperbolic and parabolic models, and the types of bifurcations present or lost when taking the parabolic limit. We show that the parabolic limit leads to a homogenisation of the inter-individual communication, and to a loss of bifurcation dynamics (in particular loss of Hopf bifurcations). This explains the less rich patterns exhibited by the nonlocal parabolic models. However, for multiple interacting populations, by breaking the population interchange symmetry of the model, one can preserve the Hopf bifurcations that lead to the formation of complex spatio-temporal patterns that describe moving aggregations.

  18. Directional sensing and streaming in Dictyostelium aggregation.

    PubMed

    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. PMID:27300919

  19. 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.

  20. 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.

  1. Reusing recycled aggregates in structural concrete

    NASA Astrophysics Data System (ADS)

    Kou, Shicong

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

  2. 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

  3. Blood viscosity: influence of erythrocyte aggregation.

    PubMed

    Chien, S; Usami, S; Dellenback, R J; Gregersen, M I; Nanninga, L B; Guest, M M

    1967-08-18

    The addition of purified canine or bovine fibrinogen to suspensions of canine erythocytes in Ringer solution caused an increase in viscosity and the formation of aggregates of erythocytes. Both of these effects became increasingly pronounced as the fibrinogen concentration was raised, and they approached plateaus with 1 gram of fibrinogen per 100 milliliters. An increase in shear rate (or shear stress) reduced both the effect on viscosity and the aggregate size. The data suggest that fibrinogen causes an increase in blood viscosity and a departure from Newtonian behavior by interacting with erythrocytes to form cell aggregates which can be dispersed by shear stress. PMID:17842794

  4. Directional sensing and streaming in Dictyostelium aggregation.

    PubMed

    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. 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.

  6. Interference between Coulombic and CT-mediated couplings in molecular aggregates: H- to J-aggregate transformation in perylene-based π-stacks.

    PubMed

    Hestand, Nicholas J; Spano, Frank C

    2015-12-28

    The spectroscopic differences between J and H-aggregates are traditionally attributed to the spatial dependence of the Coulombic coupling, as originally proposed by Kasha. However, in tightly packed molecular aggregates wave functions on neighboring molecules overlap, leading to an additional charge transfer (CT) mediated exciton coupling with a vastly different spatial dependence. The latter is governed by the nodal patterns of the molecular LUMOs and HOMOs from which the electron (te) and hole (th) transfer integrals derive. The sign of the CT-mediated coupling depends on the sign of the product teth and is therefore highly sensitive to small (sub-Angstrom) transverse displacements or slips. Given that Coulombic and CT-mediated couplings exist simultaneously in tightly packed molecular systems, the interference between the two must be considered when defining J and H-aggregates. Generally, such π-stacked aggregates do not abide by the traditional classification scheme of Kasha: for example, even when the Coulomb coupling is strong the presence of a similarly strong but destructively interfering CT-mediated coupling results in "null-aggregates" which spectroscopically resemble uncoupled molecules. Based on a Frenkel/CT Holstein Hamiltonian that takes into account both sources of electronic coupling as well as intramolecular vibrations, vibronic spectral signatures are developed for integrated Frenkel/CT systems in both the perturbative and resonance regimes. In the perturbative regime, the sign of the lowest exciton band curvature, which rigorously defines J and H-aggregation, is directly tracked by the ratio of the first two vibronic peak intensities. Even in the resonance regime, the vibronic ratio remains a useful tool to evaluate the J or H nature of the system. The theory developed is applied to the reversible H to J-aggregate transformations recently observed in several perylene bisimide systems.

  7. 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.

  8. Polling places, pharmacies, and public health: Vote & Vax 2012.

    PubMed

    Shenson, Douglas; Moore, Ryan T; Benson, William; Anderson, Lynda A

    2015-06-01

    US national elections, which draw sizable numbers of older voters, take place during flu-shot season and represent an untapped opportunity for large-scale delivery of vaccinations. In 2012, Vote & Vax deployed a total of 1585 clinics in 48 states; Washington, DC; Guam; Puerto Rico; and the US Virgin Islands. Approximately 934 clinics were located in pharmacies, and 651 were near polling places. Polling place clinics delivered significantly more vaccines than did pharmacies (5710 vs 3669). The delivery of vaccines was estimated at 9379, and approximately 45% of the recipients identified their race/ethnicity as African American or Hispanic. More than half of the White Vote & Vax recipients and more than two thirds of the non-White recipients were not regular flu shot recipients. PMID:25879150

  9. Polling places, pharmacies, and public health: Vote & Vax 2012.

    PubMed

    Shenson, Douglas; Moore, Ryan T; Benson, William; Anderson, Lynda A

    2015-06-01

    US national elections, which draw sizable numbers of older voters, take place during flu-shot season and represent an untapped opportunity for large-scale delivery of vaccinations. In 2012, Vote & Vax deployed a total of 1585 clinics in 48 states; Washington, DC; Guam; Puerto Rico; and the US Virgin Islands. Approximately 934 clinics were located in pharmacies, and 651 were near polling places. Polling place clinics delivered significantly more vaccines than did pharmacies (5710 vs 3669). The delivery of vaccines was estimated at 9379, and approximately 45% of the recipients identified their race/ethnicity as African American or Hispanic. More than half of the White Vote & Vax recipients and more than two thirds of the non-White recipients were not regular flu shot recipients.

  10. Polling Places, Pharmacies, and Public Health: Vote & Vax 2012

    PubMed Central

    Shenson, Douglas; Moore, Ryan T.; Benson, William; Anderson, Lynda A.

    2015-01-01

    US national elections, which draw sizable numbers of older voters, take place during flu-shot season and represent an untapped opportunity for large-scale delivery of vaccinations. In 2012, Vote & Vax deployed a total of 1585 clinics in 48 states; Washington, DC; Guam; Puerto Rico; and the US Virgin Islands. Approximately 934 clinics were located in pharmacies, and 651 were near polling places. Polling place clinics delivered significantly more vaccines than did pharmacies (5710 vs 3669). The delivery of vaccines was estimated at 9379, and approximately 45% of the recipients identified their race/ethnicity as African American or Hispanic. More than half of the White Vote & Vax recipients and more than two thirds of the non-White recipients were not regular flu shot recipients. PMID:25879150

  11. First record of a spawning aggregation for the tropical eastern Pacific endemic grouper Mycteroperca olfax in the Galapagos Marine Reserve.

    PubMed

    Salinas-de-León, P; Rastoin, E; Acuña-Marrero, D

    2015-07-01

    This study provides direct and indirect evidence of temporally and spatially consistent spawning aggregations for the grouper Mycteroperca olfax. Recently reported declines in population numbers, probably related to the direct targeting of aggregations by artisanal fishermen, highlight the urgent need for species-specific management actions in the Galapagos Marine Reserve, such as minimum and maximum landing sizes, and the importance of protecting key aggregation sites with the declaration of no-take areas and the establishment of total fishing bans during the reproductive season.

  12. Fractal aggregates induced by liposome-liposome interaction in the presence of Ca2+.

    PubMed

    Sabín, J; Prieto, G; Ruso, J M; Sarmiento, F

    2007-10-01

    We present a study of the fractal dimension of clusters of large unilamellar vesicles (LUVs) formed by egg yolk phosphatidylcholine (EYPC), dimyristoylphosphocholine (DMPC) and dipalmitoylphosphocholine (DPPC) induced by Ca2+ . Fractal dimensions were calculated by application of two methods, measuring the angular dependency of the light scattered by the clusters and following the evolution of the cluster size. In all cases, the fractal dimensions fell in the range from 2.1 to 1.8, corresponding to two regimes: diffusion-limited cluster aggregation (DLCA) and reaction-limited cluster aggregation (RLCA). Whereas DMPC clusters showed a typical transition from the RLCA to the DLCA aggregation, EYPC exhibited an unusual behaviour, since the aggregation was limited for a higher concentration than the critical aggregation concentration. The behaviour of DPPC was intermediate, with a transition from the RLCA to the DLCA regimes with cluster sizes depending on Ca2+ concentration. Studies on the reversibility of the aggregates show that EYPC and DPPC clusters can be re-dispersed by dilution with water. DMPC does not present reversibility. Reversibility is evidence of the existence of secondary minima in the DLVO potential between two liposomes. To predict these secondary minima, a correction of the DLVO model was necessary taking into account a repulsive force of hydration.

  13. 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 %).

  14. Using intramolecular disulfide bonds in tau protein to deduce structural features of aggregation-resistant conformations.

    PubMed

    Walker, Sophie; Ullman, Orly; Stultz, Collin M

    2012-03-16

    Because tau aggregation likely plays a role in a number of neurodegenerative diseases, understanding the processes that affect tau aggregation is of considerable importance. One factor that has been shown to influence the aggregation propensity is the oxidation state of the protein itself. Tau protein, which contains two naturally occurring cysteine residues, can form both intermolecular disulfide bonds and intramolecular disulfide bonds. Several studies suggest that intermolecular disulfide bonds can promote tau aggregation in vitro. By contrast, although there are data to suggest that intramolecular disulfide bond formation retards tau aggregation in vitro, the precise mechanism underlying this observation remains unclear. While it has been hypothesized that a single intramolecular disulfide bond in tau leads to compact conformations that cannot form extended structure consistent with tau fibrils, there are few data to support this conjecture. In the present study we generate oxidized forms of the truncation mutant, K18, which contains all four microtubule binding repeats, and isolate the monomeric fraction, which corresponds to K18 monomers that have a single intramolecular disulfide bond. We study the aggregation propensity of the oxidized monomeric fraction and relate these data to an atomistic model of the K18 unfolded ensemble. Our results argue that the main effect of intramolecular disulfide bond formation is to preferentially stabilize conformers within the unfolded ensemble that place the aggregation-prone tau subsequences, PHF6* and PHF6, in conformations that are inconsistent with the formation of cross-β-structure. These data further our understanding of the precise structural features that retard tau aggregation.

  15. Observations and modelling of microphysical variability, aggregation and sedimentation in tropical anvil cirrus outflow regions

    NASA Astrophysics Data System (ADS)

    Gallagher, M. W.; Connolly, P. J.; Crawford, I.; Heymsfield, A.; Bower, K. N.; Choularton, T. W.; Allen, G.; Flynn, M. J.; Vaughan, G.; Hacker, J.

    2012-07-01

    Aircraft measurements of the microphysics of a tropical convective anvil (at temperatures ~-60 °C) forming above the Hector storm, over the Tiwi Islands, Northern Australia, have been conducted with a view to determining ice crystal aggregation efficiencies from in situ measurements. The observed microphysics have been compared to an explicit bin-microphysical model of the anvil region, which includes crystal growth by vapour diffusion and aggregation and the process of differential sedimentation. It has been found in flights made using straight and level runs perpendicular to the storm that the number of ice crystals initially decreased with distance from the storm as aggregation took place resulting in larger crystals, followed by their loss from the cloud layer due to sedimentation. The net result was that the mass (i.e. Ice Water Content) in the anvil Ci cloud decreased, but also that the average particle size (weighted by number) remained relatively constant along the length of the anvil outflow. Comparisons with the explicit microphysics model showed that the changes in the shapes of the ice crystal spectra as a function of distance from the storm could be explained by the model if the aggregation efficiency was set to values of Eagg~0.5 and higher. This result is supported by recent literature on aggregation efficiencies for complex ice particles and suggests that either the mechanism of particle interlocking is important to the aggregation process, or that other effects are occuring, such as enhancement of ice-aggregation by high electric fields that arise as a consequence of charge separation within the storm. It is noteworthy that this value of the ice crystal aggregation efficiency is much larger than values used in cloud resolving models at these temperatures, which typically use E~0.0016. These results are important to understanding how cold clouds evolve in time and for the treatment of the evolution of tropical Ci in numerical models.

  16. Take Your Leadership Role Seriously.

    ERIC Educational Resources Information Center

    School Administrator, 1986

    1986-01-01

    The principal authors of a new book, "Profiling Excellence in America's Schools," state that leadership is the single most important element for effective schools. The generic skills of leaders are flexibility, autonomy, risk taking, innovation, and commitment. Exceptional principals and teachers take their leadership and management roles…

  17. Taking Over a Broken Program

    ERIC Educational Resources Information Center

    Grabowski, Carl

    2008-01-01

    Taking over a broken program can be one of the hardest tasks to take on. However, working towards a vision and a common goal--and eventually getting there--makes it all worth it in the end. In this article, the author shares the lessons she learned as the new director for the Bright Horizons Center in Ashburn, Virginia. She suggests that new…

  18. Taking Chances in Romantic Relationships

    ERIC Educational Resources Information Center

    Elliott, Lindsey; Knox, David

    2016-01-01

    A 64 item Internet questionnaire was completed by 381 undergraduates at a large southeastern university to assess taking chances in romantic relationships. Almost three fourths (72%) self-identified as being a "person willing to take chances in my love relationship." Engaging in unprotected sex, involvement in a "friends with…

  19. Nanoscale Ionic Aggregate Morphology in Zwitterionic Copolymers

    NASA Astrophysics Data System (ADS)

    Choi, Jae-Hong; Huyck, Rebecca; Salas-de La Cruz, David; Long, Timothy E.; Winey, Karen I.

    2009-03-01

    The morphology of two different zwitterionic copolymers, poly(sulfobetaine methacrylate-ran-butyl acrylate), and poly(sulfobetaine methacrylamide-ran-butyl acrylate) are investigated as a function of the mol % content of SBMA (7 and 9 mol %) and SBMAm (6, 10 and 13 mol %), respectively. In both copolymers, X-ray scattering results show a new structure in the material arising from ionic aggregates. The sizes of the ionic aggregates are obtained through the scattering model. The sizes of the ionic aggregates increase as the ion content increases. The application of scanning transmission electron microscopy to the study of ionomer morphology has enabled direct, model-independent visualization of the ionic aggregates. The correlation between X-ray scattering results and the real space imaging for morphology of these zwitterionic copolymers will be presented.

  20. 31 CFR 1023.313 - Aggregation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... ENFORCEMENT NETWORK, DEPARTMENT OF THE TREASURY RULES FOR BROKERS OR DEALERS IN SECURITIES Reports Required To Be Made By Brokers or Dealers in Securities § 1023.313 Aggregation. Refer to § 1010.313 of this... securities....

  1. 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.

  2. 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

  3. 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.

  4. Anger expression correlates with platelet aggregation.

    PubMed

    Wenneberg, S R; Schneider, R H; Walton, K G; MacLean, C R; Levitsky, D K; Mandarino, J V; Waziri, R; Wallace, R K

    1997-01-01

    Potential relationships between increased platelet aggregability and such psychological characteristics as hostility and anger were investigated as part of a larger intervention study investigating the potential efficacy of stress-reduction treatments. Participants performed 6-minute mental arithmetic tests under time pressure. Blood was sampled during the first minute of the task and whole blood platelet aggregation was measured in an aggregometer, using collagen and ADP. To assess anger and hostility, the authors used Spielberger's State-Trait Anger and Anger Expression scales together with the Cook-Medley Hostility Scale. The authors found positive correlations between collagen-induced platelet aggregation and outwardly expressed anger, as measured by the Anger Expression Scale. The findings suggested that modes of anger expression may be associated with increased platelet aggregation. If confirmed by future studies, this finding could provide a mechanism for the putative connection between anger/hostility and coronary heart disease.

  5. 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.

  6. Blue-emitting pyrene-based aggregates.

    PubMed

    Valera, Jorge S; Calbo, Joaquín; Gómez, Rafael; Ortí, Enrique; Sánchez, Luis

    2015-06-25

    The supramolecular polymerization of pyrene imidazoles 1 and 2, governed by H-bonding and C-H···π interactions, yields aggregates showing the characteristic bluish emission pattern of pyrene-based monomers.

  7. 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.

  8. Aggregation of magnetic microparticles in the context of targeted therapies actuated by a magnetic resonance imaging system

    NASA Astrophysics Data System (ADS)

    Mathieu, Jean-Baptiste; Martel, Sylvain

    2009-08-01

    A study of magnetic aggregation in the context of magnetic resonance imaging (MRI) based actuated targeting is proposed. MRI systems can induce displacement forces on magnetized particles as they flow through the blood vessels. Magnetic aggregation of the particles happens when they are placed within the magnetic field of the MRI system and can greatly influence the MRI steering dynamics of magnetic particles. In this paper, a review of the different parameters that can be used to tailor the size, geometry, stiffness, and density of magnetic aggregates is proposed. Then, magnetic aggregation experiments on a suspension of Fe3O4 microparticles ranging from 0.1 to 100 μm in diameter are described. The effects of particle concentration, flow rate, and magnetic field amplitude were evaluated. Field amplitudes of 1.5 mT, 0.4 T, and 1.5 T fields were applied without any magnetic steering gradients and caused aggregates that could sometimes exceed 1 mm in length. Since magnetic aggregates can reach higher magnetophoretic velocities than individual particles, large aggregates could be exploited in larger arteries with important blood flows. A few strategies are discussed to assist in the design of MRI steering experiments by enhancing the positive effects of magnetic aggregation over its negative effects.

  9. Kinetics of red blood cell aggregation: an example of geometric polymerization

    SciTech Connect

    Perelson, A.S.; Samsel, R.W.

    1984-04-02

    The kinetics of the process by which red blood cells aggregate into long cylindrical, and sometimes branched, structures called rouleaux is studied within the framework of both reversible and irreversible addition and condensation polymerization reactions. However, unlike usual polymer kinetics, here we take into account the geometry of the subunits and the geometry of the growing structure. Geometric factors such as the amount of reactive wall area influence the probability of branching and hence the final shape of the aggregate. The inclusion of loop formation reactions is shown to be crucial in obtaining physically realistic equilibrium solutions of the kinetic equations. 11 references, 3 figures.

  10. 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

  11. Low aggregation state diminishes ferrihydrite reactivity

    NASA Astrophysics Data System (ADS)

    Braunschweig, Juliane; Heister, Katja; Meckenstock, Rainer U.

    2013-04-01

    Ferrihydrite is an abundant iron(oxy)hydroxide in soils and sediments and plays an important role in microbial iron cycling due to its high reactivity. Therefore, it is often synthesized and used in geomicrobiological and mineralogical studies. The reactivities of synthetic ferrihydrites vary between different studies and synthesis protocols. Hence, we synthesized five different ferrihydrites and characterized them with XRD, FTIR, XPS, and BET specific surface area. The reactivity of the ferrihydrite samples towards ascorbic acid was examined and compared with microbial reduction rates by Geobacter sulfurreducens. FTIR and XRD results show the presence of secondary, higher crystalline iron oxide phases like goethite and akaganeite for two samples. Consequently, those samples revealed lower biotic and abiotic reduction rates compared to pure ferrihydrite. Comparison of reduction rates with the specific surface area of all ferrihydrites showed neither correlation with abiotic reductive dissolution nor with microbial reduction. Especially one sample, characterized by a very low aggregation state and presence of secondary minerals, revealed a poor reactivity. We speculate that apart from the occurring secondary minerals also the low aggregation state played an important role. Decreasing aggregation diminishes the amount of kinks and edges on the surfaces, which are produced at contact sites in aggregates. According to dissolution theories, dissolution mainly starts at those surface defects and slows down with decreasing amount of defects. Furthermore, the non-aggregated ferrihydrite is free of micropores, a further stimulant for dissolution. Independent repetitions of experiments and syntheses according to the same protocol but without formation of secondary minerals, confirmed the low reactivity of the non-aggregated ferrihydrite. In summary, our results indicate that a decreasing aggregation state of ferrihydrite to a certain size does increase the reactivity

  12. 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).

  13. J-aggregate formation of a water-soluble porphyrin in acidic aqueous media

    NASA Astrophysics Data System (ADS)

    Ohno, Osamu; Kaizu, Youkoh; Kobayashi, Hiroshi

    1993-09-01

    J aggregate of a water-soluble porphyrin, 5,10,15,20-tetra(4-sulfophenyl)porphyrin (H2TPPS44-), formed in acidified aqueous solutions, exhibits sharp and intense absorption bands at 491 and 707 nm. These characteristic transitions, J bands, are of linear oscillators polarized in the long axis of rodlike aggregate. The molecules in the aggregate stack so as to lift the degeneracy of the porphyrin planar oscillator excited states. Measurements of flow-induced linear dichroism, circular dichroism, magnetic circular dichroism, as well as polarized fluorescence excitation spectra provide evidence not only of linear oscillator character of the intense J band at 491 nm, but also of presence of another diffuse absorption band around at 420 nm polarized in the short axis of the aggregate, which is the counterpart of the 491 nm band of porphyrin Soret origin. Extrinsic circular dichroism is induced upon addition of L-tartaric acid or by mechanical swirling flow in the period of aggregate growth. Resonance Raman spectrum of the aggregate is rather similar to that of the monomeric diacid except the polarization. The observed shifts of Raman peaks to lower frequency are ascribed to a deformation of porphyrin moiety and/or hydrophobic interaction between component molecules in the aggregate. The sharp and intense J bands polarized in the long axis of aggregate cannot be well described without taking into account the participation of interporphyrin charge resonance excited states, whereas the broadbands polarized in the short axis are exclusively ascribed to exciton resonance excited states. The porphyrin J band is characterized as sustaining an exchange narrowing by fast migration of excitation over the whole system of chromophores in a linear array of the porphyrin planar oscillators in slipped face-to-face stacking.

  14. Protein sequences encode safeguards against aggregation.

    PubMed

    Reumers, Joke; Maurer-Stroh, Sebastian; Schymkowitz, Joost; Rousseau, Fréderic

    2009-03-01

    Functional requirements shaped proteins into globular structures. Under these structural constraints, which require both regular secondary structure and a hydrophobic core, protein aggregation is an unavoidable corollary to protein structure. However, as aggregation results in reduced fitness, natural selection will tend to eliminate strongly aggregating sequences. The analysis of distribution and variation of aggregation patterns in the human proteome using the TANGO algorithm confirms the findings of a previous study on several proteomes: the flanks of aggregation-prone regions are enriched with charged residues and proline, the so-called gatekeeper-residues. Moreover, in this study, we observed a widespread redundancy in gatekeeper usage. Interestingly, aggregating regions from key proteins such as p53 or huntingtin are among the most extensive "gatekept" sequences. As a consequence, mutations that remove gatekeepers could therefore result in a strong increase in disease-susceptibility. In a set of disease-associated mutations from the UniProt database, we find a strong enrichment of mutations that disrupt gatekeeper motifs. Closer inspection of a number of case studies indicates clearly that removing gatekeepers may play a determining role in widely varying disorders, such as van der Woude syndrome (VWS), X-linked Fabry disease (FD), and limb-girdle muscular dystrophy. PMID:19156839

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. Proline inhibits aggregation during protein refolding.

    PubMed Central

    Samuel, D.; Kumar, T. K.; Ganesh, G.; Jayaraman, G.; Yang, P. W.; Chang, M. M.; Trivedi, V. D.; Wang, S. L.; Hwang, K. C.; Chang, D. K.; Yu, C.

    2000-01-01

    The in vitro refolding of hen egg-white lysozyme is studied in the presence of various osmolytes. Proline is found to prevent aggregation during protein refolding. However, other osmolytes used in this study fail to exhibit a similar property. Experimental evidence suggests that proline inhibits protein aggregation by binding to folding intermediate(s) and trapping the folding intermediate(s) into enzymatically inactive, "aggregation-insensitive" state(s). However, elimination of proline from the refolded protein mixture results in significant recovery of the bacteriolytic activity. At higher concentrations (>1.5 M), proline is shown to form loose, higher-order molecular aggregate(s). The supramolecular assembly of proline is found to possess an amphipathic character. Formation of higher-order aggregates is believed to be crucial for proline to function as a protein folding aid. In addition to its role in osmoregulation under water stress conditions, the results of this study hint at the possibility of proline behaving as a protein folding chaperone. PMID:10716186

  20. Using Mnemonics to Learn Place Geography.

    ERIC Educational Resources Information Center

    Bednarz, Sarah W.

    1995-01-01

    Learning place geography is an important part of school geography. Reports on research findings addressing effective ways to teach place geography. Finds that research indicates significant differences between mnemonic and non-mnemonic treatment groups. (CFR)

  1. Secondary Lesson Plan: Place and Relative Location.

    ERIC Educational Resources Information Center

    Crawford, John

    1989-01-01

    Presents a secondary education geography lesson plan for teaching the theme of place and relative location. Provides samples of student materials. Using Japan as an example, shows how place and relative location can be used to study a country. (KO)

  2. 47 CFR 0.481 - Place of filing applications for radio authorizations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Place of filing applications for radio authorizations. 0.481 Section 0.481 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL COMMISSION... Taking Examinations § 0.481 Place of filing applications for radio authorizations. For locations...

  3. 29 CFR 780.140 - Place of performing the practice as a factor.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... STANDARDS ACT General Scope of Agriculture âsuch Farming Operationâ-of the Farmer § 780.140 Place of performing the practice as a factor. So long as the farming operations to which a farmer's practice pertains... altered by the fact that the farming operations take place on more than one farm or by the fact that...

  4. 29 CFR 780.140 - Place of performing the practice as a factor.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... STANDARDS ACT General Scope of Agriculture âsuch Farming Operationâ-of the Farmer § 780.140 Place of performing the practice as a factor. So long as the farming operations to which a farmer's practice pertains... altered by the fact that the farming operations take place on more than one farm or by the fact that...

  5. 29 CFR 780.140 - Place of performing the practice as a factor.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... STANDARDS ACT General Scope of Agriculture âsuch Farming Operationâ-of the Farmer § 780.140 Place of performing the practice as a factor. So long as the farming operations to which a farmer's practice pertains... altered by the fact that the farming operations take place on more than one farm or by the fact that...

  6. 29 CFR 780.140 - Place of performing the practice as a factor.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... STANDARDS ACT General Scope of Agriculture âsuch Farming Operationâ-of the Farmer § 780.140 Place of performing the practice as a factor. So long as the farming operations to which a farmer's practice pertains... altered by the fact that the farming operations take place on more than one farm or by the fact that...

  7. 29 CFR 780.140 - Place of performing the practice as a factor.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... STANDARDS ACT General Scope of Agriculture âsuch Farming Operationâ-of the Farmer § 780.140 Place of performing the practice as a factor. So long as the farming operations to which a farmer's practice pertains... altered by the fact that the farming operations take place on more than one farm or by the fact that...

  8. 47 CFR 0.481 - Place of filing applications for radio authorizations.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Place of filing applications for radio authorizations. 0.481 Section 0.481 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL COMMISSION... Taking Examinations § 0.481 Place of filing applications for radio authorizations. For locations...

  9. Thinking outside the Box: Placing Park and Recreation Professionals in K-12 Schools

    ERIC Educational Resources Information Center

    Dustin, Daniel; Hibbler, Dan; McKenney, Alexis; Blitzer, Laura

    2004-01-01

    The authors argue that it is time to place park and recreation professionals in K-12 schools on a permanent basis. Their proposal is based on the following observations: (1) school facilities are grossly underutilized; (2) the majority of a child's life takes place outside the classroom; (3) park and recreation programs are effective "hooks" for…

  10. 5 CFR 919.520 - Who places the information into the EPLS?

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... List System § 919.520 Who places the information into the EPLS? Federal officials who take actions to... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Who places the information into the EPLS? 919.520 Section 919.520 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT (CONTINUED)...

  11. 47 CFR 0.481 - Place of filing applications for radio authorizations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Place of filing applications for radio authorizations. 0.481 Section 0.481 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL COMMISSION... Taking Examinations § 0.481 Place of filing applications for radio authorizations. For locations...

  12. 47 CFR 0.481 - Place of filing applications for radio authorizations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Place of filing applications for radio authorizations. 0.481 Section 0.481 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL COMMISSION... Taking Examinations § 0.481 Place of filing applications for radio authorizations. For locations...

  13. 47 CFR 0.481 - Place of filing applications for radio authorizations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Place of filing applications for radio authorizations. 0.481 Section 0.481 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL COMMISSION... Taking Examinations § 0.481 Place of filing applications for radio authorizations. For locations...

  14. 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

  15. An aggregation sensing reporter identifies leflunomide and teriflunomide as polyglutamine aggregate inhibitors

    PubMed Central

    Fuentealba, Rodrigo A.; Marasa, Jayne; Diamond, Marc I.; Piwnica-Worms, David; Weihl, Conrad C.

    2012-01-01

    Intracellular protein aggregation is a common pathologic feature in neurodegenerative diseases such as Huntington' disease, amyotrophic lateral sclerosis and Parkinson' disease. Although progress towards understanding protein aggregation in vitro has been made, little of this knowledge has translated to patient therapy. Moreover, mechanisms controlling aggregate formation and catabolism in cellulo remain poorly understood. One limitation is the lack of tools to quantitatively monitor protein aggregation and disaggregation. Here, we developed a protein-aggregation reporter that uses huntingtin exon 1 containing 72 glutamines fused to the N-terminal end of firefly luciferase (httQ72-Luc). httQ72-Luc fails to aggregate unless seeded by a non-luciferase-containing polyglutamine (polyQ) protein such as Q80-cfp. Upon co-aggregation, httQ72-luc becomes insoluble and loses its enzymatic activity. Using httQ72-Luc with Q80(CFP/YFP) as seeds, we screened the Johns Hopkins Clinical Compound Library and identified leflunomide, a dihydroorotate dehydrogenase inhibitor with immunosuppressive and anti-psoriatic activities, as a novel drug that prevents polyQ aggregation. Leflunomide and its active metabolite teriflunomide inhibited protein aggregation independently of their known role in pyrimidine biosynthesis, since neither uridine treatment nor other pyrimidine biosynthesis inhibitors affected polyQ aggregation. Inducible cell line and cycloheximide-chase experiments indicate that these drugs prevent incorporation of expanded polyQ into an aggregate. This study demonstrates the usefulness of luciferase-based protein aggregate reporters for high-throughput screening applications. As current trials are under-way for teriflunomide in the treatment of multiple sclerosis, we propose that this drug be considered a possible therapeutic agent for polyQ diseases. PMID:22052286

  16. Hawaii Play Fairway Analysis: Hawaiian Place Names

    SciTech Connect

    Nicole Lautze

    2015-11-15

    Compilation of Hawaiian place names indicative of heat. Place names are from the following references: Pukui, M.K., and S.H. Elbert, 1976, Place Names of Hawaii, University of Hawaii Press, Honolulu, HI 96822, 289 pp. ; Bier, J. A., 2009, Map of Hawaii, The Big Island, Eighth Edition, University of Hawaii Press, Honolulu, HI  96822, 1 sheet.; and Reeve, R., 1993, Kahoolawe Place Names, Consultant Report No. 16, Kahoolawe Island Conveyance Commission, 259 pp.

  17. 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

  18. Northwest Literature and a Sense of Place.

    ERIC Educational Resources Information Center

    Simonson, Harold P.

    Teachers should help students gain a sense of where they stand. It is difficult to imagine literature without a sense of place--places bridge time and evoke and recreate the past. To compose is to remember, to recreate, and a sense of place begins the composing. Some northwestern U.S. books illustrate the point. In a college literature class,…

  19. Anthropological Studies of Native American Place Names.

    ERIC Educational Resources Information Center

    Thornton, Thomas F.

    1997-01-01

    Traces development of Native American place name studies from Boas (1880s) to the present. Argues that place names convey information about physical environments but also reveal how people perceive, conceptualize, and utilize their environment. Suggests the utility of place names as a framework for cultural analysis and describes recent…

  20. Sense of Place in Environmental Education

    ERIC Educational Resources Information Center

    Kudryavtsev, Alex; Stedman, Richard C.; Krasny, Marianne E.

    2012-01-01

    Although environmental education research has embraced the idea of sense of place, it has rarely taken into account environmental psychology-based sense of place literature whose theory and empirical studies can enhance related studies in the education context. This article contributes to research on sense of place in environmental education from…

  1. Literacy, Place and the Digital World

    ERIC Educational Resources Information Center

    Green, Bill

    2012-01-01

    Observing that place may be understood in a range of sometimes conflicting ways, the paper picks up on recent work within literacy studies on notions of place-making and locational disadvantage to argue for increasingly sophisticated and reflexive uses of place in the field, as a counterpoint to both increasing educational standardisation and…

  2. Growth, Politics, and the Stratification of Places

    ERIC Educational Resources Information Center

    Logan, John R.

    1978-01-01

    Systematic inequalities among interdependent places are described as a dimension of stratification of persons and organizations. Concludes that territorial differentiation is influenced by political action, that place is often an important basis of collective action, and that places consciously attempt to influence growth in desired directions.…

  3. Using PlacesOnline in Instructional Activities

    ERIC Educational Resources Information Center

    Longan, Michael W.; Owusu, Francis; Roseman, Curtis C.

    2008-01-01

    PlacesOnLine.org is a Web portal that provides easy access to high quality Web sites that focus on places from around the world. It is intended for use by a wide range of people, including professional geographers, teachers and students at all levels, and the general public. This article explores the potential uses of PlacesOnLine as an…

  4. The Space Place: Adventures in Informal Education - and Lessons Learned

    NASA Astrophysics Data System (ADS)

    Fisher, D.; Leon, N.

    2001-12-01

    products both economical and comprehensive. While the Space Place effort started as a New Millennium Program effort, it was quickly expanded to all NASA missions who wish to participate. The team soon realized that the informal education community wanted a variety of content - not just more and more information about a few missions, but rather a continuous infusion of new content from new missions. This expansion of the Space Place program allows any mission to take advantage of the existing Space Place infrastructure and alliances - and provides the much-needed variety of materials that the informal education community desires. This poster session will provide an overview of the Space Place effort within the informal education community, and will illustrate some of the valuable lessons learned by the team in working with this rich and varied community.

  5. Teaching Kids with Learning Disabilities to Take Public Transit

    ERIC Educational Resources Information Center

    Schoenfeld, Jane

    2009-01-01

    Taking public transit can make anyone nervous, especially in a large or medium-sized city where there are many different bus lines going many different places. The author's daughter, Anna, has multiple learning disabilities and may never learn to drive, but she wants to be as independent as possible so the author taught her to ride the bus. This…

  6. Taking Research into Schools: The West Lothian Action Enquiry Model

    ERIC Educational Resources Information Center

    Binnie, Lynne M.; Allen, Kristen; Beck, Elaine

    2008-01-01

    This paper outlines the efforts of an Educational Psychology Service (EPS) to develop its practice in the area of research. It will argue that the Action Enquiry model of service delivery can empower teaching staff and may allow an effective means of change and improvement to take place in schools. This model steers research towards providing…

  7. Naratriptan aggregation in lipid bilayers: perspectives from molecular dynamics simulations.

    PubMed

    Wood, Irene; Pickholz, Mónica

    2016-09-01

    In order to understand the interaction between naratriptan and a fully hydrated bilayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidyl-choline (POPC), we carried out molecular dynamics simulations. The simulations were performed considering neutral and protonated ionization states, starting from different initial conditions. At physiological pH, the protonated state of naratriptan is predominant. It is expected that neutral compounds could have larger membrane partition than charged compounds. However, for the specific case of triptans, it is difficult to study neutral species in membranes experimentally, making computer simulations an interesting tool. When the naratriptan molecules were originally placed in water, they partitioned between the bilayer/water interface and water phase, as has been described for similar compounds. From this condition, the drugs displayed low access to the hydrophobic environment, with no significant effects on bilayer organization. The molecules anchored in the interface, due mainly to the barrier function of the polar and oriented lipid heads. On the other hand, when placed inside the bilayer, both neutral and protonated naratriptan showed self-aggregation in the lipid tail environment. In particular, the protonated species exhibited a pore-like structure, dragging water through this environment. Graphical Abstract Different behaviour of Naratriptan and Sumatriptan, when the drugs were originally placed in the lipid core. PMID:27558798

  8. Role of protein conformation and aggregation in pumping water in and out of a cell.

    PubMed

    Cameron, I L; Kanal, K M; Fullerton, G D

    2006-01-01

    Dialysis cassettes containing BSA solutions were used to simulate passive in vivo conditions to assess the effect of protein conformation and aggregation on cell water content. The cassettes were suspended in dextran solutions to provide a range of fixed osmotic stress values simulating blood plasma. The system was placed on a shaker for 24 h to attain equilibrium. Four manipulation methods; pH, cosolute salt concentration, e.g. NaCl, temperature annealing and urea concentration denaturant were varied to produce well-known manipulations of BSA conformation. It was observed that the cell water content varied from +14% to about -13% with changes in protein conformation and aggregation. The findings demonstrate that a change in protein conformation and aggregation, pumps water in and out of a cell to maintain equilibrium % water content matching the protein conformational hydration parameter. This concept supplements existing theories on cell volume regulation. PMID:16376581

  9. Role of protein conformation and aggregation in pumping water in and out of a cell.

    PubMed

    Cameron, I L; Kanal, K M; Fullerton, G D

    2006-01-01

    Dialysis cassettes containing BSA solutions were used to simulate passive in vivo conditions to assess the effect of protein conformation and aggregation on cell water content. The cassettes were suspended in dextran solutions to provide a range of fixed osmotic stress values simulating blood plasma. The system was placed on a shaker for 24 h to attain equilibrium. Four manipulation methods; pH, cosolute salt concentration, e.g. NaCl, temperature annealing and urea concentration denaturant were varied to produce well-known manipulations of BSA conformation. It was observed that the cell water content varied from +14% to about -13% with changes in protein conformation and aggregation. The findings demonstrate that a change in protein conformation and aggregation, pumps water in and out of a cell to maintain equilibrium % water content matching the protein conformational hydration parameter. This concept supplements existing theories on cell volume regulation.

  10. Taking medicines to treat tuberculosis

    MedlinePlus

    ... drugs. This is called directly observed therapy. Side Effects and Other Problems Women who may be pregnant, who are pregnant, or who are breastfeeding should talk to their provider before taking these ...

  11. Taking Action for Healthy Kids.

    ERIC Educational Resources Information Center

    Kidd, Jill E.

    2003-01-01

    Summarizes research on relationship between physical activity, good nutrition, and academic performance. Offers several recommendations for how schools can take action to improve the nutrition and fitness of students. (PKP)

  12. LRO Takes the Moon's Temperature

    NASA Video Gallery

    During the December 2011 lunar eclipse, LRO's Diviner instrument will take the temperature on the lunar surface. Since different rock sizes cool at different rates, scientists will be able to infer...

  13. LRO Takes the Moon's Temperature

    NASA Video Gallery

    During the June 2011 lunar eclipse, scientists will be able to get a unique view of the moon. While the sun is blocked by the Earth, LRO's Diviner instrument will take the temperature on the lunar ...

  14. Taking America To New Heights

    NASA Video Gallery

    NASA's Commercial Crew Program (CCP) is taking America to new heights with its Commercial Crew Development Round 2 (CCDev2) partners. In 2011, NASA entered into funded Space Act Agreements (SAAs) w...

  15. Structural determinants of Tau aggregation inhibitor potency.

    PubMed

    Schafer, Kelsey N; Cisek, Katryna; Huseby, Carol J; Chang, Edward; Kuret, Jeff

    2013-11-01

    Small-molecule Tau aggregation inhibitors are under investigation as potential therapeutic agents against Alzheimer disease. Many such inhibitors have been identified in vitro, but their potency-driving features, and their molecular targets in the Tau aggregation pathway, have resisted identification. Previously we proposed ligand polarizability, a measure of electron delocalization, as a candidate descriptor of inhibitor potency. Here we tested this hypothesis by correlating the ground state polarizabilities of cyanine, phenothiazine, and arylmethine derivatives calculated using ab initio quantum methods with inhibitory potency values determined in the presence of octadecyl sulfate inducer under reducing conditions. A series of rhodanine analogs was analyzed as well using potency values disclosed in the literature. Results showed that polarizability and inhibitory potency directly correlated within all four series. To identify putative binding targets, representative members of the four chemotypes were added to aggregation reactions, where they were found to stabilize soluble, but SDS-resistant Tau species at the expense of filamentous aggregates. Using SDS resistance as a secondary assay, and a library of Tau deletion and missense mutants as targets, interaction with cyanine was localized to the microtubule binding repeat region. Moreover, the SDS-resistant phenotype was completely dependent on the presence of octadecyl sulfate inducer, but not intact PHF6/PH6* hexapeptide motifs, indicating that cyanine interacted with a species in the aggregation pathway prior to nucleus formation. Together the data suggest that flat, highly polarizable ligands inhibit Tau aggregation by interacting with folded species in the aggregation pathway and driving their assembly into soluble but highly stable Tau oligomers.

  16. Structural Determinants of Tau Aggregation Inhibitor Potency*

    PubMed Central

    Schafer, Kelsey N.; Cisek, Katryna; Huseby, Carol J.; Chang, Edward; Kuret, Jeff

    2013-01-01

    Small-molecule Tau aggregation inhibitors are under investigation as potential therapeutic agents against Alzheimer disease. Many such inhibitors have been identified in vitro, but their potency-driving features, and their molecular targets in the Tau aggregation pathway, have resisted identification. Previously we proposed ligand polarizability, a measure of electron delocalization, as a candidate descriptor of inhibitor potency. Here we tested this hypothesis by correlating the ground state polarizabilities of cyanine, phenothiazine, and arylmethine derivatives calculated using ab initio quantum methods with inhibitory potency values determined in the presence of octadecyl sulfate inducer under reducing conditions. A series of rhodanine analogs was analyzed as well using potency values disclosed in the literature. Results showed that polarizability and inhibitory potency directly correlated within all four series. To identify putative binding targets, representative members of the four chemotypes were added to aggregation reactions, where they were found to stabilize soluble, but SDS-resistant Tau species at the expense of filamentous aggregates. Using SDS resistance as a secondary assay, and a library of Tau deletion and missense mutants as targets, interaction with cyanine was localized to the microtubule binding repeat region. Moreover, the SDS-resistant phenotype was completely dependent on the presence of octadecyl sulfate inducer, but not intact PHF6/PH6* hexapeptide motifs, indicating that cyanine interacted with a species in the aggregation pathway prior to nucleus formation. Together the data suggest that flat, highly polarizable ligands inhibit Tau aggregation by interacting with folded species in the aggregation pathway and driving their assembly into soluble but highly stable Tau oligomers. PMID:24072703

  17. Characterization of Ovine Dermal Papilla Cell Aggregation

    PubMed Central

    Sari, Agnes Rosarina Prita; Rufaut, Nicholas Wolfgang; Jones, Leslie Norman; Sinclair, Rodney Daniel

    2016-01-01

    Context: The dermal papilla (DP) is a condensation of mesenchymal cells at the proximal end of the hair follicle, which determines hair shaft size and regulates matrix cell proliferation and differentiation. DP cells have the ability to regenerate new hair follicles. These cells tend to aggregate both in vitro and in vivo. This tendency is associated with the ability of papilla cells to induce hair growth. However, human papilla cells lose their hair-inducing activity in later passage number. Ovine DP cells are different from human DP cells since they do not lose their aggregative behavior or hair-inducing activity in culture. Nonetheless, our understanding of ovine DP cells is still limited. Aim: The aim of this study was to observe the expression of established DP markers in ovine cells and their association with aggregation. Subjects and Methods: Ovine DP cells from three different sheep were compared. Histochemistry, immunoflourescence, and polymerase chain reaction experiments were done to analyze the DP markers. Results: We found that ovine DP aggregates expressed all the 16 markers evaluated, including alkaline phosphatase and versican. Expression of the versican V0 and V3 isoforms, neural cell adhesion molecule, and corin was increased significantly with aggregation, while hey-1 expression was significantly decreased. Conclusions: Overall, the stable expression of numerous markers suggests that aggregating ovine DP cells have a similar phenotype to papillae in vivo. The stability of their molecular phenotype is consistent with their robust aggregative behavior and retained follicle-inducing activity after prolonged culture. Their phenotypic stability in culture contrasts with DP cells from other species, and suggests that a better understanding of ovine DP cells might provide opportunities to improve the hair-inducing activity and therapeutic potential of human cells. PMID:27625564

  18. Characterization of Ovine Dermal Papilla Cell Aggregation

    PubMed Central

    Sari, Agnes Rosarina Prita; Rufaut, Nicholas Wolfgang; Jones, Leslie Norman; Sinclair, Rodney Daniel

    2016-01-01

    Context: The dermal papilla (DP) is a condensation of mesenchymal cells at the proximal end of the hair follicle, which determines hair shaft size and regulates matrix cell proliferation and differentiation. DP cells have the ability to regenerate new hair follicles. These cells tend to aggregate both in vitro and in vivo. This tendency is associated with the ability of papilla cells to induce hair growth. However, human papilla cells lose their hair-inducing activity in later passage number. Ovine DP cells are different from human DP cells since they do not lose their aggregative behavior or hair-inducing activity in culture. Nonetheless, our understanding of ovine DP cells is still limited. Aim: The aim of this study was to observe the expression of established DP markers in ovine cells and their association with aggregation. Subjects and Methods: Ovine DP cells from three different sheep were compared. Histochemistry, immunoflourescence, and polymerase chain reaction experiments were done to analyze the DP markers. Results: We found that ovine DP aggregates expressed all the 16 markers evaluated, including alkaline phosphatase and versican. Expression of the versican V0 and V3 isoforms, neural cell adhesion molecule, and corin was increased significantly with aggregation, while hey-1 expression was significantly decreased. Conclusions: Overall, the stable expression of numerous markers suggests that aggregating ovine DP cells have a similar phenotype to papillae in vivo. The stability of their molecular phenotype is consistent with their robust aggregative behavior and retained follicle-inducing activity after prolonged culture. Their phenotypic stability in culture contrasts with DP cells from other species, and suggests that a better understanding of ovine DP cells might provide opportunities to improve the hair-inducing activity and therapeutic potential of human cells.

  19. Lipid vesicle aggregation induced by cooling.

    PubMed

    Howard, Frank B; Levin, Ira W

    2010-01-01

    Lipid bilayer fusion is a complex process requiring several intermediate steps. Initially, the two bilayers are brought into close contact following removal of intervening water layers and overcoming electrostatic repulsions between opposing bilayer head groups. In this study we monitor by light scattering the reversible aggregation of phosphatidylcholine single shell vesicles during which adhesion occurs but stops prior to a fusion process. Light scattering measurements of dimyristoyl-sn-glycero-3-phosphocholine (DMPC), dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) in water show that lowering the temperature of about 0.14 micron single shell vesicles of DPPC (from 20 degrees C to 5 degrees C) and about 2 micron vesicles of DSPC (from 20 degrees C to 15 degrees C), but not of 1 micron vesicles of DMPC, results in extensive aggregation within 24 hours that is reversible by an increase in temperature. Aggregation of DSPC vesicles was confirmed by direct visual observation. Orientation of lipid head groups parallel to the plane of the bilayer and consequent reduction of the negative surface charge can account for the ability of DPPC and DSPC vesicles to aggregate. Retention of negatively charged phosphates on the surface and the burial of positively charged cholines within the bilayer offer an explanation for the failure of DMPC vesicles to aggregate. Lowering the temperature of 1,2-dipalmitoyl-sn-glycero-3-phosphoserine (DPPS) vesicles from 20 degrees C to 5 degrees C failed to increase aggregation within 24 hours at Mg(++)/DPPS ratios that begin to initiate aggregation and fusion.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  1. Constraints on the Birth Aggregate of the Solar System

    NASA Astrophysics Data System (ADS)

    Adams, Fred C.; Laughlin, Gregory

    2001-03-01

    Using the observed properties of our Solar System, in particular the isotopic compositions of meteorites and the regularity of the planetary orbits, we constrain the star formation environment of the Sun within the scenario of (external) radioactive enrichment by a massive star. This calculation yields a probability distribution for the number of stars in the solar birth aggregate. The Sun is most likely to have formed within a stellar group containing N=< N>≈2000±1100 members. The a priori probability of a star forming in this type of environment is P≈0.0085; i.e., only about 1 out of 120 solar systems are expected to form under similar conditions. We discuss additional implications of this scenario, including possible effects from the radiation fields provided by the putative cluster environment and dynamical disruption of the Kuiper Belt. The constraints of this paper place tight restrictions on the properties of the solar birth aggregate for the scenario of external enrichment by a massive star; alternately, these tight constraints slightly favor a self-enrichment scenario for the short-lived radioactive species.

  2. Constraints on the Birth Aggregate of the Solar System

    NASA Astrophysics Data System (ADS)

    Adams, F. C.; Laughlin, G.

    2002-09-01

    Using the observed properties of our solar system -- the isotopic compositions of meteorites and the regularity of the planetary orbits -- we constrain the star formation environment of the Sun within the scenario of (external) radioactive enrichment by a massive star. This calculation yields a probability distribution for the number of stars in the solar birth aggregate. The Sun is most likely to have formed within a stellar group containing N=2000 members. The probability of a star forming in this type of environment is P = 0.0085, i.e., only about 1 out of 120 solar systems are expected to form under similar conditions. We discuss implications of this scenario, including possible effects from the radiation fields provided by the putative cluster environment and dynamical disruption of the Kuiper Belt. The constraints of this paper place tight restrictions on the properties of the solar birth aggregate for the scenario of external enrichment by a massive star; alternately, these tight constraints slightly favor a self-enrichment scenario for the short-lived radioactive species.

  3. An improved procedure for determination of the mean aggregation number of micelles

    NASA Astrophysics Data System (ADS)

    Wu, Shuangyan; Tachiya, Masanori; Yan, Zhenning

    2015-03-01

    In this paper, a theory of fluorescence quenching in micelles which enables a dynamic approach to the evaluation of the aggregation numbers of micelles is presented. This method is based on a detailed kinetic model of quenching of fluorescent probe developed by Tachiya (1975, 1982) and takes into account that a part of quenchers are associated with micelles but the remaining quenchers are in the aqueous phase. The approach presented is an improvement on a previous fluorescence quenching method (Turro and Yekta, 1978) and is applied to determine the aggregation number of sodium dodecyl sulfonate (SAS) in aqueous dipeptide solution using cetylpyridinium chloride as quencher. The values of aggregation number and association constant for quencher-micelle association are presented.

  4. Hesitant fuzzy linguistic multicriteria decision-making method based on generalized prioritized aggregation operator.

    PubMed

    Wu, Jia-ting; Wang, Jian-qiang; Wang, Jing; Zhang, Hong-yu; Chen, Xiao-hong

    2014-01-01

    Based on linguistic term sets and hesitant fuzzy sets, the concept of hesitant fuzzy linguistic sets was introduced. The focus of this paper is the multicriteria decision-making (MCDM) problems in which the criteria are in different priority levels and the criteria values take the form of hesitant fuzzy linguistic numbers (HFLNs). A new approach to solving these problems is proposed, which is based on the generalized prioritized aggregation operator of HFLNs. Firstly, the new operations and comparison method for HFLNs are provided and some linguistic scale functions are applied. Subsequently, two prioritized aggregation operators and a generalized prioritized aggregation operator of HFLNs are developed and applied to MCDM problems. Finally, an illustrative example is given to illustrate the effectiveness and feasibility of the proposed method, which are then compared to the existing approach.

  5. Stoichiometry and Physical Chemistry of Promiscuous Aggregate-Based Inhibitors

    PubMed Central

    Coan, Kristin E. D.

    2009-01-01

    Many false positives in early drug discovery owe to nonspecific inhibition by colloid-like aggregates of organic molecules. Despite their prevalence, little is known about aggregate concentration, structure, or dynamic equilibrium; the binding mechanism, stoichiometry with, and affinity for enzymes remain uncertain. To investigate the elementary question of concentration, we counted aggregate particles using flow cytometry. For seven aggregate-forming molecules, aggregates were not observed until the concentration of monomer crossed a threshold, indicating a “critical aggregation concentration” (CAC). Above the CAC, aggregate count increased linearly with added organic material, while the particles dispersed when diluted below the CAC. The concentration of monomeric organic molecule is constant above the CAC, as is the size of the aggregate particles. For two compounds that form large aggregates, nicardipine and miconazole, we measured particle numbers directly by flow cytometry, determining that the aggregate concentration just above the CAC ranged from 5 to 30 fM. By correlating inhibition of an enzyme with aggregate count for these two drugs, we determined that the stoichiometry of binding is about 10 000 enzyme molecules per aggregate particle. Using measured volumes for nicardipine and miconazole aggregate particles (2.1 × 1011 and 4.7 × 1010 Å3, respectively), computed monomer volumes, and the observation that past the CAC all additional monomer forms aggregate particles, we find that aggregates are densely packed particles. Finally, given their size and enzyme stoichiometry, all sequestered enzyme can be comfortably accommodated on the surface of the aggregate. PMID:18588298

  6. Structure and aggregation in model tetramethylurea solutions

    SciTech Connect

    Gupta, Rini; Patey, G. N.

    2014-08-14

    The structure of model aqueous tetramethylurea (TMU) solutions is investigated employing large-scale (32 000, 64 000 particles) molecular dynamics simulations. Results are reported for TMU mole fractions, X{sub t}, ranging from infinite dilution up to 0.07, and for two temperatures, 300 and 330 K. Two existing force fields for TMU-water solutions are considered. These are the GROMOS 53A6 united-atom TMU model combined with SPC/E water [TMU(GROMOS-UA)/W(SPC/E)], and the more frequently employed AMBER03 all-atom force field for TMU combined with the TIP3P water model [TMU(AMBER-AA)/W(TIP3P)]. It is shown that TMU has a tendency towards aggregation for both models considered, but the tendency is significantly stronger for the [TMU(AMBER-AA)/W(TIP3P)] force field. For this model signs of aggregation are detected at X{sub t} = 0.005, aggregation is a well established feature of the solution at X{sub t} = 0.02, and the aggregates increase further in size with increasing concentration. This is in agreement with at least some experimental studies, which report signals of aggregation in the low concentration regime. The TMU aggregates exhibit little structure and are simply loosely ordered, TMU-rich regions of solution. The [TMU(GROMOS-UA)/W(SPC/E)] model shows strong signs of aggregation only at higher concentrations (X{sub t} ≳ 0.04), and the aggregates appear more loosely ordered, and less well-defined than those occurring in the [TMU(AMBER-AA)/W(TIP3P)] system. For both models, TMU aggregation increases when the temperature is increased from 300 to 330 K, consistent with an underlying entropy driven, hydrophobic interaction mechanism. At X{sub t} = 0.07, the extra-molecular correlation length expected for microheterogeneous solutions has become comparable with the size of the simulation cell for both models considered, indicating that even the systems simulated here are sufficiently large only at low concentrations.

  7. Metaconcrete: Engineered aggregates for enhanced dynamic performance

    NASA Astrophysics Data System (ADS)

    Mitchell, Stephanie J.

    This work presents the development and investigation of a new type of concrete for the attenuation of waves induced by dynamic excitation. Recent progress in the field of metamaterials science has led to a range of novel composites which display unusual properties when interacting with electromagnetic, acoustic, and elastic waves. A new structural metamaterial with enhanced properties for dynamic loading applications is presented, which is named metaconcrete. In this new composite material the standard stone and gravel aggregates of regular concrete are replaced with spherical engineered inclusions. Each metaconcrete aggregate has a layered structure, consisting of a heavy core and a thin compliant outer coating. This structure allows for resonance at or near the eigenfrequencies of the inclusions, and the aggregates can be tuned so that resonant oscillations will be activated by particular frequencies of an applied dynamic loading. The activation of resonance within the aggregates causes the overall system to exhibit negative effective mass, which leads to attenuation of the applied wave motion. To investigate the behavior of metaconcrete slabs under a variety of different loading conditions a finite element slab model containing a periodic array of aggregates is utilized. The frequency dependent nature of metaconcrete is investigated by considering the transmission of wave energy through a slab, which indicates the presence of large attenuation bands near the resonant frequencies of the aggregates. Applying a blast wave loading to both an elastic slab and a slab model that incorporates the fracture characteristics of the mortar matrix reveals that a significant portion of the supplied energy can be absorbed by aggregates which are activated by the chosen blast wave profile. The transfer of energy from the mortar matrix to the metaconcrete aggregates leads to a significant reduction in the maximum longitudinal stress, greatly improving the ability of the material

  8. The Mechanisms of Aberrant Protein Aggregation

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  9. Rotating bacteria aggregate into active crystals

    NASA Astrophysics Data System (ADS)

    Petroff, Alexander; Wu, Xiao-Lun; Libchaber, Albert

    2014-11-01

    The dynamics of many microbial ecosystems are determined not only by the response of individual bacteria to their chemical and physical environments but also the dynamics that emerge from interactions between cells. Here we investigate the collective dynamics displayed by communities of Thiovulum majus, one of the fastest known bacteria. We observe that when these bacteria swim close to a microscope cover slip, the cells spontaneously aggregate into a visually-striking two-dimensional hexagonal lattice of rotating cells. Each cell in an aggregate rotates its flagella, exerting a force that pushes the cell into the cover slip and a torque that causes the cell to rotate. As cells rotate against their neighbors, they exert forces and torques on the aggregate that cause the crystal to move and cells to hop to new positions in the lattice. We show how these dynamics arises from hydrodynamic and surface forces between cells. We derive the equations of motion for an aggregate, show that this model reproduces many aspects of the observed dynamics, and discuss the stability of these and similar active crystals. Finally, we discuss the ecological significance of this behavior to understand how the ability to aggregate into these communities may have evolved.

  10. Rotating Bacteria Aggregate into Active Crystals

    NASA Astrophysics Data System (ADS)

    Petroff, A. P.; Wu, X. L.; Libchaber, A.

    2014-12-01

    The dynamics of many microbial ecosystems are determined not only by the response of individual bacteria to their chemical and physical environments but also the dynamics that emerge from interactions between cells. Here we investigate collective dynamics displayed by communities of Thiovulum majus, one of the fastest known bacteria. We observe that when these bacteria swim close to a microscope cover slip, the cells spontaneously aggregate into a visually-striking, two-dimensional hexagonal lattice of rotating cells. Each cell in an aggregate rotates its flagella, exerting a force that pushes the cell into the cover slip and a torque that causes the cell to rotate. As cells rotate against their neighbors, they exert forces and torques on the aggregate that cause the crystal to move and cells to hop to new positions in the lattice. We show how these dynamics arise from hydrodynamic and surface forces between cells. We derive the equations of motion for an aggregate, show that this model reproduces many aspects of the observed dynamics, and discuss the stability of these and similar active crystals. Finally, we discuss the ecological significance of this behavior to understand how the ability to aggregate into these communities may have evolved.

  11. Particle aggregation with simultaneous surface growth

    SciTech Connect

    pablo.mitchell@cal.Berkeley.EDU

    2003-04-29

    Particle aggregation with simultaneous surface growth was modeled using a dynamic Monte Carlo method. The Monte Carlo algorithm begins in the particle inception zone and constructs aggregates via ensemble-averaged collisions between spheres and deposition of gaseous species on the sphere surfaces. Simulations were conducted using four scenarios. The first, referred to as scenario 0, is used as a benchmark and simulates aggregation in the absence of surface growth. Scenario 1 forces all balls to grow at a uniform rate while scenario 2 only permits them to grow once they have collided and stuck to each other. The last one is a test scenario constructed to confirm conclusions drawn from scenarios 0-2. The transition between the coalescent and the fully-developed fractal aggregation regimes is investigated using shape descriptors to quantify particle geometry. They are used to define the transition between the coalescent and fractal growth regimes. The simulations demonstrate that the morphology of aggregating particles is intimately related to both the surface deposition and particle nucleation rates.

  12. Static compression of porous dust aggregates

    NASA Astrophysics Data System (ADS)

    Kataoka, Akimasa; Tanaka, Hidekazu; Okuzumi, Satoshi; Wada, Koji

    2013-07-01

    To understand the structure evolution of dust aggregates is a key in the planetesimal formation. Dust grains become fluffy by coagulation in protoplanetary disks. However, once they become fluffy, they are not sufficiently compressed by collisional compression to form compact planetesimals (Okuzumi et al. 2012, ApJ, 752, 106). Thus, some other compression mechanisms are required to form planetesimals. We investigate the static compression of highly porous aggregates. First, we derive the compressive strength by numerical N-body simulations (Kataoka et al. 2013, A&A, 554, 4). Then, we apply the strength to protoplanetary disks, supposing that the highly porous aggregates can be quiasi-statically compressed by ram pressure of the disk gas and the self gravity. As a result, we find the pathway of the dust structure evolution from dust grains via fluffy aggregates to compact planetesimals. Moreover, we find that the fluffy aggregates overcome the barriers in planetesimal formation, which are radial drift, fragmentation, and bouncing barriers. (The paper is now available on arXiv: http://arxiv.org/abs/1307.7984 )

  13. Modes of Star Formation and Constraints on the Birth Aggregate of our Solar System

    NASA Astrophysics Data System (ADS)

    Adams, Fred C.

    This work suggests that star forming environments should be classified into finer divisions than the traditional isolated and clustered modes. Using the observed open cluster system, we estimate the fraction of star formation that takes place within cluster environments: Only about 10% of the stellar population originates from star forming regions destined to become open clusters. The smallest clusters included in the observational surveys (containing N˜100-300 members) roughly coincide with the smallest stellar systems that evolve as clusters in a dynamical sense. Specifically, we show that stellar systems with too few members N < N * have dynamical relaxation times that are shorter than their formation times (˜1-2 Myr), where the critical number of stars N * ≈ 100. Our results thus suggest that star formation can be characterized by (at least) three principal modes: [I] isolated singles and binaries, [II] groups (N < N *), and [III] clusters (N > N *). Many - if not most - stars form through the intermediate mode in stellar groups with 10 < N < N_* ˜ 100. The groups evolve and disperse much more rapidly than do open clusters and thus represent a different type of astronomical entity. Furthermore, groups and clusters affect star formation in different ways. Groups have a low probability of containing massive stars and are thus unaffected by supernovae and intense ultraviolet radiation fields. In addition, interactions between the young stellar objects are relatively rare in groups because of their short lifetimes and small stellar membership. Finally, we can apply these considerations to the formation of our own solar system and thereby find tight constraints on the solar birth aggregate.

  14. Mechanisms of carbon nanotube aggregation and the reversion of carbon nanotube aggregates in aqueous medium.

    PubMed

    Koh, Byumseok; Cheng, Wei

    2014-09-16

    Single-walled carbon nanotubes (SWCNTs) dispersed in aqueous medium have many potential applications in chemistry, biology, and medicine. Reversible aggregation of SWCNTs dispersed in water has been frequently reported, but the mechanisms behind are not well understood. Here we show that SWCNTs dispersed into aqueous medium assisted by various charged molecules can be reversibly aggregated by a variety of electrolytes with two distinct mechanisms. Direct binding of counterions to SWCNTs leads to aggregation when the surface charge is neutralized from 74 to 86%. This aggregation is driven by electrostatic instead of van der Waals interactions, thus showing similarity to that of DNA condensation induced by multivalent cations. Sequestration of counterions by chelating reagents leads to the redispersion of SWCNT aggregates. In contrast to various metal ions, polyelectrolytes have the unique ability to induce SWCNT aggregation by bridging between individual SWCNTs. Aggregation through the latter mechanism can be engineered to be reversible by exploiting various mechanisms of chain breaking, including reduction of disulfide bond in the polymer chain, and the cleavage action of proteolytic enzymes. These findings clarify the mechanisms of SWCNT aggregation, and have broad implications in various applications of SWCNTs in water. PMID:25144606

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

    ERIC Educational Resources Information Center

    Elwood, S. Kirk

    2001-01-01

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

  16. Protein aggregation and lyophilization: Protein structural descriptors as predictors of aggregation propensity

    PubMed Central

    Roughton, Brock C.; Iyer, Lavanya K.; Bertelsen, Esben; Topp, Elizabeth M.; Camarda, Kyle V.

    2014-01-01

    Lyophilization can induce aggregation in therapeutic proteins, but the relative importance of protein structure, formulation and processing conditions are poorly understood. To evaluate the contribution of protein structure to lyophilization-induced aggregation, fifteen proteins were co-lyophilized with each of five excipients. Extent of aggregation following lyophilization, measured using size-exclusion chromatography, was correlated with computational and biophysical protein structural descriptors via multiple linear regression. Descriptor selection was performed using exhaustive search and forward selection. The results demonstrate that, for a given excipient, extent of aggregation is highly correlated by eight to twelve structural descriptors. Leave-one-out cross validation showed that the correlations were able to successfully predict the aggregation for a protein “left out” of the data set. Selected descriptors varied with excipient, indicating both protein structure and excipient type contribute to lyophilization-induced aggregation. The results show some descriptors used to predict protein aggregation in solution are useful in predicting lyophilized protein aggregation. PMID:24516290

  17. Aggregation Pheromone System: A Real-parameter Optimization Algorithm using Aggregation Pheromones as the Base Metaphor

    NASA Astrophysics Data System (ADS)

    Tsutsui, Shigeyosi

    This paper proposes an aggregation pheromone system (APS) for solving real-parameter optimization problems using the collective behavior of individuals which communicate using aggregation pheromones. APS was tested on several test functions used in evolutionary computation. The results showed APS could solve real-parameter optimization problems fairly well. The sensitivity analysis of control parameters of APS is also studied.

  18. Interference between Coulombic and CT-mediated couplings in molecular aggregates: H- to J-aggregate transformation in perylene-based π-stacks

    SciTech Connect

    Hestand, Nicholas J.; Spano, Frank C.

    2015-12-28

    The spectroscopic differences between J and H-aggregates are traditionally attributed to the spatial dependence of the Coulombic coupling, as originally proposed by Kasha. However, in tightly packed molecular aggregates wave functions on neighboring molecules overlap, leading to an additional charge transfer (CT) mediated exciton coupling with a vastly different spatial dependence. The latter is governed by the nodal patterns of the molecular LUMOs and HOMOs from which the electron (t{sub e}) and hole (t{sub h}) transfer integrals derive. The sign of the CT-mediated coupling depends on the sign of the product t{sub e}t{sub h} and is therefore highly sensitive to small (sub-Angstrom) transverse displacements or slips. Given that Coulombic and CT-mediated couplings exist simultaneously in tightly packed molecular systems, the interference between the two must be considered when defining J and H-aggregates. Generally, such π-stacked aggregates do not abide by the traditional classification scheme of Kasha: for example, even when the Coulomb coupling is strong the presence of a similarly strong but destructively interfering CT-mediated coupling results in “null-aggregates” which spectroscopically resemble uncoupled molecules. Based on a Frenkel/CT Holstein Hamiltonian that takes into account both sources of electronic coupling as well as intramolecular vibrations, vibronic spectral signatures are developed for integrated Frenkel/CT systems in both the perturbative and resonance regimes. In the perturbative regime, the sign of the lowest exciton band curvature, which rigorously defines J and H-aggregation, is directly tracked by the ratio of the first two vibronic peak intensities. Even in the resonance regime, the vibronic ratio remains a useful tool to evaluate the J or H nature of the system. The theory developed is applied to the reversible H to J-aggregate transformations recently observed in several perylene bisimide systems.

  19. Caspase-Mediated Truncation of Tau Potentiates Aggregation

    PubMed Central

    Lee, Sangmook; Shea, Thomas B.

    2012-01-01

    Caspase-mediated truncation of tau is associated with aggregation. We examined the impact of manipulation of caspase activity on intracellular aggregation of a mutant form of tau (3PO) that forms spontaneous aggregates. Treatment with the caspase inhibitor Z-VAD-fmk reduced both N and C-terminal tau truncation but did not significantly reduce aggregation. Treatment with staurosporine, which activated caspases, increased C-terminal but not N-terminal truncation and enhanced aggregation. These findings suggest that caspase activation is one potential route, rather than an obligatory initiation step, in aggregation, and that N- and C-terminal truncation contribute differentially to aggregation. PMID:22988541

  20. Cellular strategies for regulating functional and nonfunctional protein aggregation.

    PubMed

    Gsponer, Jörg; Babu, M Madan

    2012-11-29

    Growing evidence suggests that aggregation-prone proteins are both harmful and functional for a cell. How do cellular systems balance the detrimental and beneficial effect of protein aggregation? We reveal that aggregation-prone proteins are subject to differential transcriptional, translational, and degradation control compared to nonaggregation-prone proteins, which leads to their decreased synthesis, low abundance, and high turnover. Genetic modulators that enhance the aggregation phenotype are enriched in genes that influence expression homeostasis. Moreover, genes encoding aggregation-prone proteins are more likely to be harmful when overexpressed. The trends are evolutionarily conserved and suggest a strategy whereby cellular mechanisms specifically modulate the availability of aggregation-prone proteins to (1) keep concentrations below the critical ones required for aggregation and (2) shift the equilibrium between the monomeric and oligomeric/aggregate form, as explained by Le Chatelier's principle. This strategy may prevent formation of undesirable aggregates and keep functional assemblies/aggregates under control. PMID:23168257