Factors Affecting Training Transfer: Participants' Motivation to Transfer Training, Literature Review

ERIC Educational Resources Information Center

Alawneh, Muhammad K.

2008-01-01

This article investigates factors that motivate participants in learning and training activities to transfer skills, knowledge and attitude from the learning setting to the workplace. Based on training transfer theories hypothesized by Holton (1996), one of the major theories that affect an organization's learning is motivation to transfer theory.…

Expression of organophosphorus-degradation gene ( opd) in aggregating and non-aggregating filamentous nitrogen-fixing cyanobacteria

NASA Astrophysics Data System (ADS)

Li, Qiong; Tang, Qing; Xu, Xudong; Gao, Hong

2010-11-01

Genetic engineering in filamentous N2-fixing cyanobacteria usually involves Anabaena sp. PCC 7120 and several other non-aggregating species. Mass culture and harvest of such species are more energy consuming relative to aggregating species. To establish a gene transfer system for aggregating species, we tested many species of Anabaena and Nostoc, and identified Nostoc muscorum FACHB244 as a species that can be genetically manipulated using the conjugative gene transfer system. To promote biodegradation of organophosphorus pollutants in aquatic environments, we introduced a plasmid containing the organophosphorus-degradation gene ( opd) into Anabaena sp. PCC 7120 and Nostoc muscorum FACHB244 by conjugation. The opd gene was driven by a strong promoter, P psbA . From both species, we obtained transgenic strains having organophosphorus-degradation activities. At 25°C, the whole-cell activities of the transgenic Anabaena and Nostoc strains were 0.163±0.001 and 0.289±0.042 unit/μg Chl a, respectively. However, most colonies resulting from the gene transfer showed no activity. PCR and DNA sequencing revealed deletions or rearrangements in the plasmid in some of the colonies. Expression of the green fluorescent protein gene from the same promoter in Anabaena sp. PCC 7120 showed similar results. These results suggest that there is the potential to promote the degradation of organophosphorus pollutants with transgenic cyanobacteria and that selection of high-expression transgenic colonies is important for genetic engineering of Anabaena and Nostoc species. For the first time, we established a gene transfer and expression system in an aggregating filamentous N2-fixing cyanobacterium. The genetic manipulation system of Nostoc muscorum FACHB244 could be utilized in the elimination of pollutants and large-scale production of valuable proteins or metabolites.

Quantitative analysis of intrinsic and extrinsic factors in the aggregation mechanism of Alzheimer-associated Aβ-peptide

NASA Astrophysics Data System (ADS)

Meisl, Georg; Yang, Xiaoting; Frohm, Birgitta; Knowles, Tuomas P. J.; Linse, Sara

2016-01-01

Disease related mutations and environmental factors are key determinants of the aggregation mechanism of the amyloid-β peptide implicated in Alzheimer's disease. Here we present an approach to investigate these factors through acquisition of highly reproducible data and global kinetic analysis to determine the mechanistic influence of intrinsic and extrinsic factors on the Aβ aggregation network. This allows us to translate the shift in macroscopic aggregation behaviour into effects on the individual underlying microscopic steps. We apply this work-flow to the disease-associated Aβ42-A2V variant, and to a variation in pH as examples of an intrinsic and an extrinsic perturbation. In both cases, our data reveal a shift towards a mechanism in which a larger fraction of the reactive flux goes via a pathway that generates potentially toxic oligomeric species in a fibril-catalyzed reaction. This is in agreement with the finding that Aβ42-A2V leads to early-onset Alzheimer’s disease and enhances neurotoxicity.

Aggregation factor analysis for protein formulation by a systematic approach using FTIR, SEC and design of experiments techniques.

PubMed

Feng, Yan Wen; Ooishi, Ayako; Honda, Shinya

2012-01-05

A simple systematic approach using Fourier transform infrared (FTIR) spectroscopy, size exclusion chromatography (SEC) and design of experiments (DOE) techniques was applied to the analysis of aggregation factors for protein formulations in stress and accelerated testings. FTIR and SEC were used to evaluate protein conformational and storage stabilities, respectively. DOE was used to determine the suitable formulation and to analyze both the main effect of single factors and the interaction effect of combined factors on aggregation. Our results indicated that (i) analysis at a low protein concentration is not always applicable to high concentration formulations; (ii) an investigation of interaction effects of combined factors as well as main effects of single factors is effective for improving conformational stability of proteins; (iii) with the exception of pH, the results of stress testing with regard to aggregation factors would be available for suitable formulation instead of performing time-consuming accelerated testing; (iv) a suitable pH condition should not be determined in stress testing but in accelerated testing, because of inconsistent effects of pH on conformational and storage stabilities. In summary, we propose a three-step strategy, using FTIR, SEC and DOE techniques, to effectively analyze the aggregation factors and perform a rapid screening for suitable conditions of protein formulation. Copyright © 2011 Elsevier B.V. All rights reserved.

Von Willebrand's disease with spontaneous platelet aggregation induced by an abnormal plasma von Willebrand factor.

PubMed Central

Grainick, H R; Williams, S B; McKeown, L P; Rick, M E; Maisonneuve, P; Jenneau, C; Sultan, Y

1985-01-01

We have investigated and characterized the abnormalities in four unrelated patients with von Willebrand's disease (vWd) who have (a) enhanced ristocetin-induced platelet aggregation (RIPA) at low ristocetin concentrations, (b) absence of the largest plasma von Willebrand factor (vWf) multimers, and (c) thrombocytopenia. The platelet-rich plasma of these patients aggregates spontaneously without the addition of any agonists. When isolated normal platelets are resuspended in patient plasma spontaneous aggregation occurs; however, the patients' plasmas did not induce platelet aggregation of normal washed formalinized platelets. When the patients' platelets are suspended in normal plasma, spontaneous aggregation is not observed. The spontaneous platelet aggregation (SPA) is associated with dense granule secretion as measured by ATP release and alpha granule release as measured by beta-thromboglobulin and platelet factor 4 release. The SPA is totally inhibited by 5 mM EDTA, prostaglandin I2, and dibutryl cyclic AMP, while it is only partially inhibited by 1 mM EDTA, acetylsalicylic acid, or apyrase. A monoclonal antibody directed against glycoprotein Ib (GPIb) and/or a monoclonal antibody against the glycoprotein IIb/IIIa (GPIIb/IIIa) complex totally inhibits the SPA. The vWf was isolated from the plasma of one of these patients. The purified vWf induced platelet aggregation of normal platelets resuspended in either normal or severe vWd plasma, but the vWf did not induce platelet aggregation of normal platelets resuspended in afibrinognemic plasma. Sialic acid and galactose quantification of the patient's vWf revealed approximately a 50% reduction compared with normal vWf. These studies indicate that a form of vWd exists, which is characterized by SPA that is induced by the abnormal plasma vWf. The SPA is dependent on the presence of plasma fibrinogen, and the availability of the GPIb and the GPIIb/IIIa complex. In this variant form of vWd the abnormal vWf causes

Hsp42 is required for sequestration of protein aggregates into deposition sites in Saccharomyces cerevisiae

PubMed Central

Specht, Sebastian; Miller, Stephanie B.M.

2011-01-01

The aggregation of proteins inside cells is an organized process with cytoprotective function. In Saccharomyces cerevisiae, aggregating proteins are spatially sequestered to either juxtanuclear or peripheral sites, which target distinct quality control pathways for refolding and degradation. The cellular machinery driving the sequestration of misfolded proteins to these sites is unknown. In this paper, we show that one of the two small heat shock proteins of yeast, Hsp42, is essential for the formation of peripheral aggregates during physiological heat stress. Hsp42 preferentially localizes to peripheral aggregates but is largely absent from juxtanuclear aggregates, which still form in hsp42Δ cells. Transferring the amino-terminal domain of Hsp42 to Hsp26, which does not participate in aggregate sorting, enables Hsp26 to replace Hsp42 function. Our data suggest that Hsp42 acts via its amino-terminal domain to coaggregate with misfolded proteins and perhaps link such complexes to further sorting factors. PMID:22065637

Aggregation is a critical cause of poor transfer into the brain tissue of intravenously administered cationic PAMAM dendrimer nanoparticles

PubMed Central

Kurokawa, Yoshika; Sone, Hideko; Win-Shwe, Tin-Tin; Zeng, Yang; Kimura, Hiroyuki; Koyama, Yosuke; Yagi, Yusuke; Matsui, Yasuto; Yamazaki, Masashi; Hirano, Seishiro

2017-01-01

Dendrimers have been expected as excellent nanodevices for brain medication. An amine-terminated polyamidoamine dendrimer (PD), an unmodified plain type of PD, has the obvious disadvantage of cytotoxicity, but still serves as an attractive molecule because it easily adheres to the cell surface, facilitating easy cellular uptake. Single-photon emission computed tomographic imaging of a mouse following intravenous injection of a radiolabeled PD failed to reveal any signal in the intracranial region. Furthermore, examination of the permeability of PD particles across the blood–brain barrier (BBB) in vitro using a commercially available kit revealed poor permeability of the nanoparticles, which was suppressed by an inhibitor of caveolae-mediated endocytosis, but not by an inhibitor of macropinocytosis. Physicochemical analysis of the PD revealed that cationic PDs are likely to aggregate promptly upon mixing with body fluids and that this prompt aggregation is probably driven by non-Derjaguin–Landau– Verwey–Overbeek attractive forces originating from the surrounding divalent ions. Atomic force microscopy observation of a freshly cleaved mica plate soaked in dendrimer suspension (culture media) confirmed prompt aggregation. Our study revealed poor transfer of intravenously administered cationic PDs into the intracranial nervous tissue, and the results of our analysis suggested that this was largely attributable to the reduced BBB permeability arising from the propensity of the particles to promptly aggregate upon mixing with body fluids. PMID:28579780

An Aggregate IRT Procedure for Exploratory Factor Analysis

ERIC Educational Resources Information Center

Camilli, Gregory; Fox, Jean-Paul

2015-01-01

An aggregation strategy is proposed to potentially address practical limitation related to computing resources for two-level multidimensional item response theory (MIRT) models with large data sets. The aggregate model is derived by integration of the normal ogive model, and an adaptation of the stochastic approximation expectation maximization…

Visible light-induced insulin aggregation on surfaces via photoexcitation of bound thioflavin T.

PubMed

Chouchane, Karim; Pignot-Paintrand, Isabelle; Bruckert, Franz; Weidenhaupt, Marianne

2018-04-01

Insulin is known to form amyloid aggregates when agitated in a hydrophobic container. Amyloid aggregation is routinely measured by the fluorescence of the conformational dye thioflavin T, which, when incorporated into amyloid fibers, fluoresces at 480 nm. The kinetics of amyloid aggregation in general is characterized by an initial lag-phase, during which aggregative nuclei form on the hydrophobic surface. These nuclei then lead to the formation of fibrils presenting a rapid growth during the elongation phase. Here we describe a novel mechanism of insulin amyloid aggregation which is surprisingly devoid of a lag-time for nucleation. The excitation of thioflavin T by visible light at 440 nm induces the aggregation of thioflavin T-positive insulin fibrils on hydrophobic surfaces in the presence of strong agitation and at physiological pH. This process is material surface-induced and depends on the fact that surface-adsorbed insulin can bind thioflavin T. Light-induced insulin aggregation kinetics is thioflavin T-mediated and is based on an energy transfer from visible light to the protein via thioflavin T. It relies on a constant supply of thioflavin T and insulin from the solution to the aggregate. The growth rate increases with the irradiance and with the concentration of thioflavin T. The supply of insulin seems to be the limiting factor of aggregate growth. This light-induced aggregation process allows the formation of local surface-bound aggregation patterns. Copyright © 2018 Elsevier B.V. All rights reserved.

Oxygen transport and stem cell aggregation in stirred-suspension bioreactor cultures.

PubMed

Wu, Jincheng; Rostami, Mahboubeh Rahmati; Cadavid Olaya, Diana P; Tzanakakis, Emmanuel S

2014-01-01

Stirred-suspension bioreactors are a promising modality for large-scale culture of 3D aggregates of pluripotent stem cells and their progeny. Yet, cells within these clusters experience limitations in the transfer of factors and particularly O2 which is characterized by low solubility in aqueous media. Cultured stem cells under different O2 levels may exhibit significantly different proliferation, viability and differentiation potential. Here, a transient diffusion-reaction model was built encompassing the size distribution and ultrastructural characteristics of embryonic stem cell (ESC) aggregates. The model was coupled to experimental data from bioreactor and static cultures for extracting the effective diffusivity and kinetics of consumption of O2 within mouse (mESC) and human ESC (hESC) clusters. Under agitation, mESC aggregates exhibited a higher maximum consumption rate than hESC aggregates. Moreover, the reaction-diffusion model was integrated with a population balance equation (PBE) for the temporal distribution of ESC clusters changing due to aggregation and cell proliferation. Hypoxia was found to be negligible for ESCs with a smaller radius than 100 µm but became appreciable for aggregates larger than 300 µm. The integrated model not only captured the O2 profile both in the bioreactor bulk and inside ESC aggregates but also led to the calculation of the duration that fractions of cells experience a certain range of O2 concentrations. The approach described in this study can be employed for gaining a deeper understanding of the effects of O2 on the physiology of stem cells organized in 3D structures. Such frameworks can be extended to encompass the spatial and temporal availability of nutrients and differentiation factors and facilitate the design and control of relevant bioprocesses for the production of stem cell therapeutics.

The cell aggregating propensity of probiotic actinobacterial isolates: isolation and characterization of the aggregation inducing peptide pheromone.

PubMed

Muthu Selvam, Ramu; Vinothini, Gopal; Palliyarai Thaiyammal, Sethuramalingam; Latha, Selvanathan; Chinnathambi, Arunachalam; Dhanasekaran, Dharumadurai; Padmanabhan, Parasuraman; Ali Alharbi, Sulaiman; Archunan, Govindaraju

2016-01-01

The auto-aggregating ability of a probiotic is a prerequisite for colonization and protection of the gastrointestinal tract, whereas co-aggregation provides a close interaction with pathogenic bacteria. Peptide pheromone mediated signaling has been studied in several systems. However, it has not yet been explored in prokaryotes, especially actinobacteria. Hence, in the present study, the diffusible aggregation promoting factor was purified from the culture supernatant of a potent actinobacterial probiont and characterized using 20 different actinobacterial cultures isolated from the gut region of chicken and goat. The results showed that the pheromone-like compound induces the aggregation propensity of treated isolates. The factor was found to be a heat stable, acidic pH resistant, low molecular weight peptide which enhances the biofilm forming ability of other actinobacterial isolates. The aggregation promoting factor represents a bacterial sex factor (pheromone) and its characterization confirms its usage in the probiotic formulation.

Not just fractal surfaces, but surface fractal aggregates: Derivation of the expression for the structure factor and its applications

NASA Astrophysics Data System (ADS)

Besselink, R.; Stawski, T. M.; Van Driessche, A. E. S.; Benning, L. G.

2016-12-01

Densely packed surface fractal aggregates form in systems with high local volume fractions of particles with very short diffusion lengths, which effectively means that particles have little space to move. However, there are no prior mathematical models, which would describe scattering from such surface fractal aggregates and which would allow the subdivision between inter- and intraparticle interferences of such aggregates. Here, we show that by including a form factor function of the primary particles building the aggregate, a finite size of the surface fractal interfacial sub-surfaces can be derived from a structure factor term. This formalism allows us to define both a finite specific surface area for fractal aggregates and the fraction of particle interfacial sub-surfaces at the perimeter of an aggregate. The derived surface fractal model is validated by comparing it with an ab initio approach that involves the generation of a "brick-in-a-wall" von Koch type contour fractals. Moreover, we show that this approach explains observed scattering intensities from in situ experiments that followed gypsum (CaSO4 ṡ 2H2O) precipitation from highly supersaturated solutions. Our model of densely packed "brick-in-a-wall" surface fractal aggregates may well be the key precursor step in the formation of several types of mosaic- and meso-crystals.

Femtosecond fluorescence dynamics of porphyrin in solution and solid films: the effects of aggregation and interfacial electron transfer between porphyrin and TiO2.

PubMed

Luo, Liyang; Lo, Chen-Fu; Lin, Ching-Yao; Chang, I-Jy; Diau, Eric Wei-Guang

2006-01-12

The excited-state relaxation dynamics of a synthetic porphyrin, ZnCAPEBPP, in solution, coated on a glass substrate as solid films, mixed with PMMA and coated on a glass substrate as solid films, and sensitized on nanocrystalline TiO2 films were investigated by using femtosecond fluorescence up-conversion spectroscopy with excitation in the Soret band, S2. We found that the S2--> S1 electronic relaxation of ZnCAPEBPP in solution and on PMMA films occurs in 910 and 690 fs, respectively, but it becomes extremely rapid, <100 fs, in solid films and TiO2 films due to formation of porphyrin aggregates. When probed in the S1 state of porphyrin, the fluorescence transients of the solid films show a biphasic kinetic feature with the rapid and slow components decaying in 1.9-2.4 and 19-26 ps, respectively. The transients in ZnCAPEBPP/TiO2 films also feature two relaxation processes but they occur on different time scales, 100-300 fs and 0.8-4.1 ps, and contain a small offset. According to the variation of relaxation period as a function of molecular density on a TiO2 surface, we assigned the femtosecond component of the TiO2 films as due to indirect interfacial electron transfer through a phenylethynyl bridge attached to one of four meso positions of the porphyrin ring, and the picosecond component arising from intermolecular energy transfer among porphyrins. The observed variation of aggregate-induced relaxation periods between solid and TiO2 films is due mainly to aggregation of two types: J-type aggregation is dominant in the former case whereas H-type aggregation prevails in the latter case.

Selective aggregation of the splicing factor Hsh155 suppresses splicing upon genotoxic stress.

PubMed

Mathew, Veena; Tam, Annie S; Milbury, Karissa L; Hofmann, Analise K; Hughes, Christopher S; Morin, Gregg B; Loewen, Christopher J R; Stirling, Peter C

2017-12-04

Upon genotoxic stress, dynamic relocalization events control DNA repair as well as alterations of the transcriptome and proteome, enabling stress recovery. How these events may influence one another is only partly known. Beginning with a cytological screen of genome stability proteins, we find that the splicing factor Hsh155 disassembles from its partners and localizes to both intranuclear and cytoplasmic protein quality control (PQC) aggregates under alkylation stress. Aggregate sequestration of Hsh155 occurs at nuclear and then cytoplasmic sites in a manner that is regulated by molecular chaperones and requires TORC1 activity signaling through the Sfp1 transcription factor. This dynamic behavior is associated with intron retention in ribosomal protein gene transcripts, a decrease in splicing efficiency, and more rapid recovery from stress. Collectively, our analyses suggest a model in which some proteins evicted from chromatin and undergoing transcriptional remodeling during stress are targeted to PQC sites to influence gene expression changes and facilitate stress recovery. © 2017 Mathew et al.

Improving the quality of miniature pig somatic cell nuclear transfer blastocysts: aggregation of SCNT embryos at the four-cell stage.

PubMed

Terashita, Y; Sugimura, S; Kudo, Y; Amano, R; Hiradate, Y; Sato, E

2011-04-01

Miniature pigs share many similar characteristics such as anatomy, physiology and body size with humans and are expected to become important animal models for therapeutic cloning using embryonic stem cells (ESCs) derived by somatic cell nuclear transfer (SCNT). In the present study, we observed that miniature pig SCNT blastocysts possessed a lower total number of nuclei and a lower percentage of POU5F1-positive cells than those possessed by in vitro fertilized (IVF) blastocysts. To overcome these problems, we evaluated the applicability of aggregating miniature pig SCNT embryos at the four-cell stage. We showed that (i) aggregation of two or three miniature pig SCNT embryos at the four-cell stage improves the total number of nuclei and the percentage of POU5F1-positive cells in blastocysts, and (ii) IVF blastocysts with low cell numbers induced by the removal of two blastomeres at the four-cell stage did not exhibit a decrease in the percentage of POU5F1-positive cells. These results suggest that the aggregation of miniature pig SCNT embryos at the four-cell stage can be a useful technique for improving the quality of miniature pig SCNT blastocysts and indicating that improvement in the percentage of POU5F1-positive cells in aggregated SCNT embryos is not simply the consequence of increased cell numbers. © 2010 Blackwell Verlag GmbH.

Superradiance of J-Aggregated 2,2'-Cyanine Absorbed onto a Vesicle Surface

NASA Technical Reports Server (NTRS)

Akins, Daniel L.; Ozcelik, Serdar

1995-01-01

Phospholipid vesicles are used as substrates to form adsorbed aggregates of 2,2'-cyanine, also referred to as pseudoisocyanine (PIC). In this paper, we report photophysical parameters of two putative adsorbed aggregates species (cis- and trans-aggregates, relating to their makeup from mono-cis and all-transstereoisomers, respectively). Phase modulation picosecond fluorescence decay measurements reveal that superradiance and energy transfer are dominant features controlling photophysical processes. Superradiance, coherence size, energy transfer and exciton-phonon coupling are discussed for the two types of aggregates; as regards photophysical parameters, the fluorescence lifetimes, fluorescence quantum yields, and nonradiative rate constants are determined. It is suggested that structure plays the crucial role in excited state dynamics.

Familial aggregation and linkage analysis with covariates for metabolic syndrome risk factors.

PubMed

Naseri, Parisa; Khodakarim, Soheila; Guity, Kamran; Daneshpour, Maryam S

2018-06-15

Mechanisms of metabolic syndrome (MetS) causation are complex, genetic and environmental factors are important factors for the pathogenesis of MetS In this study, we aimed to evaluate familial and genetic influences on metabolic syndrome risk factor and also assess association between FTO (rs1558902 and rs7202116) and CETP(rs1864163) genes' single nucleotide polymorphisms (SNP) with low HDL_C in the Tehran Lipid and Glucose Study (TLGS). The design was a cross-sectional study of 1776 members of 227 randomly-ascertained families. Selected families contained at least one affected metabolic syndrome and at least two members of the family had suffered a loss of HDL_C according to ATP III criteria. In this study, after confirming the familial aggregation with intra-trait correlation coefficients (ICC) of Metabolic syndrome (MetS) and the quantitative lipid traits, the genetic linkage analysis of HDL_C was performed using conditional logistic method with adjusted sex and age. The results of the aggregation analysis revealed a higher correlation between siblings than between parent-offspring pairs representing the role of genetic factors in MetS. In addition, the conditional logistic model with covariates showed that the linkage results between HDL_C and three marker, rs1558902, rs7202116 and rs1864163 were significant. In summary, a high risk of MetS was found in siblings confirming the genetic influences of metabolic syndrome risk factor. Moreover, the power to detect linkage increases in the one parameter conditional logistic model regarding the use of age and sex as covariates. Copyright © 2018. Published by Elsevier B.V.

Transfer factors of polonium from soil to parsley and mint.

PubMed

Al-Masri, M S; Al-Hamwi, A; Eadan, Z; Amin, Y

2010-12-01

Transfer factors of (210)Po from soil to parsley and mint have been determined. Artificial polonium isotope ((208)Po) was used as a tracer to determine transfer factor of Po from soil to plant in pot experiments. Two plant growing systems were used for this study namely, an outdoor system and a sheltered system by a polyethylene tent. (208)Po and (210)Po were determined in soil and different parts of the studied plants (stem and leaf), using alpha spectroscopy. The results have shown that there was a clear uptake of (208)Po by roots to leaves and stems of both plants. Higher values of transfer factors using the (210)Po activity concentrations than the (208)Po activity concentration were observed. Transfer factors of (210)Po from soil to parsley varied between 20 × 10⁻² and 50 × 10⁻² and 22 × 10⁻³ and 67 × 10⁻³ in mint, while (208)Po transfer factors varied between 4 × 10⁻² and 12 × 10⁻² for parsley and 10 × 10⁻² and 22 × 10⁻² in mint. Transfer factors of Po were higher in those plants grown in the sheltered system than in the open system; about 75% of Po was transferred from atmosphere to parsley parts using the two systems. Ratios of transferred Po from soil to mint stem and leaf in the sheltered system were higher by 2 times from those in the open system. Copyright © 2010 Elsevier Ltd. All rights reserved.

Inhibitory activity of aspirin on von Willebrand factor-induced platelet aggregation.

PubMed

Homoncik, M; Jilma, B; Eichelberger, B; Panzer, S

2000-09-01

The effect of aspirin (ASA) on vWF induced platelet - platelet interaction is unknown. We therefore tested the response of platelets to von Willebrand factor (vWF) coated beads induced platelet aggregation before and after i.v. and oral ASA. 1000 mg ASA was infused to 10 healthy individuals and after a wash-out period 7 volunteers received 100 mg ASA orally over a period of 11 days. Prior to ASA and in regular intervals thereafter we tested the reactivity to vWF-coated beads to assess platelet adhesion/aggregation and the fade-out time of ASA effects on platelets. Considerable interindividual variability in response to vWF-coated beads was observed, both before ASA and after treatment with ASA. The maximal response to vWF-coated beads (Tmax), the time lag, and the slope of the curve were significantly affected by i.v. ASA, whereas 100 mg of ASA had only inconstant effect on Tmax and slope. The absolute reduction of Tmax after ASA depended on the pre-ASA level, while the percentage of the reduction was similar in all individuals. Thus, platelet aggregation induced by vWF-coated beads is impaired by ASA. Furthermore, our data indicate a large interindividual variability of the response to ASA shortly after treatment induction, which becomes more constant after prolonged treatment.

Factors influencing training transfer in nursing profession: a qualitative study.

PubMed

Ma, Fang; Bai, Yangjing; Bai, Yangjuan; Ma, Weiguang; Yang, Xiangyu; Li, Jiping

2018-03-20

There is a growing recognition that training is not translated into performance and the 'transfer problem' exists in organization training today. Although factors contributing to training transfer have been identified in business and industry, the factors influencing training transfer in nursing profession remain less clear. A qualitative descriptive study was undertaken in two tertiary referral hospitals in China from February 2013 to September 2013. Purposeful sampling of 24 nursing staffs were interviewed about the factors influencing training transfer. Seven themes evolved from the analysis, categorized in 4 main domains, which described the factors influencing training transfer in nursing profession in trainee characteristics, training design, work environment and profession domain. The trainee characteristics domain included attitude and ability. The training design domain included training content and instruction method. The work environment domain included supports as facilitators and opposition as hindrance. The theme pertaining to the profession domain was professional development. Health care managers need to understand the factors influencing training transfer for maximizing the benefits of training. The right beliefs and values about training, the rigorous employee selection for training, the relevance of training content, training instructions facilitating learning and transfer, supports from peer, supervisors and the organization, organizational culture such as change, sharing, learning and support, and professional development are key to successful training transfer. Furthermore, managers should be aware of the opposition from co-workers and find ways to prevent it.

The characteristics of referring facilities and transferred hand surgery patients: factors associated with emergency patient transfers.

PubMed

Kuo, Phoebe; Hartzell, Tristan L; Eberlin, Kyle R; Miao, Diana; Zurakowski, David; Winograd, Jonathan M; Day, Charles S

2014-03-19

As emergency departments (EDs) become increasingly overwhelmed and specialist coverage in some EDs decreases, patients may be transferred to tertiary or quaternary facilities for specialized care to decrease patient load at transferring facilities. Our objective was to determine whether facilities that transferred patients for hand surgery had hand surgery coverage and to evaluate any nonmedical factors that might have been associated with transfer. A retrospective review was conducted for 1167 visits of hand and wrist patients seen in the EDs of two urban level-I trauma centers. The hand surgery capacity of referring facilities was determined by phone calls to the EDs. Univariate and multivariable analyses were conducted to identify nonmedical factors that could potentially affect the decision to transfer. A total of 155 (13.3%) of 1167 patients arrived from other facilities for specialized hand care. These patients were significantly more likely to be male (p = 0.02), have noncommercial insurance (p = 0.04), require an interpreter (p = 0.01), and arrive between 6:00 p.m. and midnight (p = 0.03). In a multivariable analysis, sex and insurance status were significantly associated with transfer (p < 0.05). The subset of ninety-five patients who were transferred from other EDs was significantly more likely to be male (p < 0.01) and arrive on weekends (p < 0.01) or between 6:00 p.m. and midnight (p < 0.01). Of these patients, seventy-seven (81%) were transferred from an ED that reported partial or full hand surgery coverage. However, only eight (10.4%) received a hand surgery evaluation prior to transfer. The low percentage of patients receiving hand surgery evaluations prior to transfer suggests that referring hospitals are not using their own hand surgeon resources. Nonmedical factors, including noncommercial insurance and off-hour time of initial arrival, may be associated with the decision to transfer patients. Identifying nonmedical factors associated

Analysis of aggregate impact factor inflation in ophthalmology.

PubMed

Caramoy, Albert; Korwitz, Ulrich; Eppelin, Anita; Kirchhof, Bernd; Fauser, Sascha

2013-01-01

To analyze the aggregate impact factor (AIF) in ophthalmology, its inflation rate, and its relation to other subject fields. A retrospective, database review of all subject fields in the Journal Citation Reports (JCR), Science edition. Citation data, AIF, number of journals and citations from the years 2003-2011 were analyzed. Data were retrieved from JCR. Future trends were calculated using a linear regression method. The AIF varies considerably between subjects. It shows also an inflation rate, which varies annually. The AIF inflation rate in ophthalmology was not as high as the background AIF inflation rate. The AIF inflation rate caused the AIF to increase annually. Not considering these variations in the AIF between years and between fields will make the AIF as a bibliometric tool inappropriate. Copyright © 2012 S. Karger AG, Basel.

Novel direct factor Xa inhibitory compounds from Tenebrio molitor with anti-platelet aggregation activity.

PubMed

Lee, Wonhwa; Kim, Mi-Ae; Park, InWha; Hwang, Jae Sam; Na, MinKyun; Bae, Jong-Sup

2017-11-01

Tenebrio molitor is an edible insect that has antimicrobial, anticancer, and antihypertensive effects. The aim of this study was to identify the unreported bioactive compounds from T. molitor larvae with inhibitory activities against factor Xa (FXa) and platelet aggregation. Isolated compounds were evaluated for their anti-FXa and anti-platelet aggregation properties by monitoring clotting time, platelet aggregation, FXa activity, and thrombus formation. A diketopiperazine (1, cyclo( L -Pro- L -Tyr)) and a phenylethanoid (2, N-acetyltyramine) were isolated and inhibited the catalytic activity of FXa in a mixed inhibition model and inhibited platelet aggregation induced by adenosine diphosphate (ADP) and U46619. They inhibited ADP- and U46619-induced phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS) and the expression of P-selectin and PAC-1 in platelets. They also improved the production of nitric oxide and inhibited the oversecretion of endothelin-1 compared to that of the ADP- or U46619-treated group. In an animal model of arterial and pulmonary thrombosis, the isolated compounds showed enhanced antithrombotic effects. They also elicited anticoagulant effects in mice. Compounds 1-2 inhibited ADP-, collagen-, or U46619-induced platelet aggregation and showed similar anti-thrombotic efficacy to rivaroxaban, a positive control. Therefore, 1-2 could serve as candidates and provide scaffolds for the development of new anti-FXa and anti-platelet drugs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural study of aggregated β-carotene by absorption spectroscopy

NASA Astrophysics Data System (ADS)

Lu, Li Ping; Wei, Liang Shu

2017-10-01

By UV-visible absorption spectroscope, the aggregated β-carotene in hydrated ethanol was studied in the temperature range of 5 55°C, with different ethanol/water ratio. And the structural evolutions of these aggregates with time were detected. The spectrophotometric analysis showed that the aggregate of β-carotene formed in 1:1 ethanol/water solution transfered from H-type to J-type with temperature increase. In 2:1 ethanol/water solution a new type of aggregate with strong coupling was predicated by the appearing absorption peak located at about 550 nm. In the time scales of 48 houses all the aggregated structures were stable, but the absorption intensity decreased with time. It was concluded that the types of aggregated β-carotene which wouldn't change with time depended on the solvent composition and temperature.

Deracemization of bilirubin as the marker of the chirality of micellar aggregates.

PubMed

Sorrenti, Alessandro; Altieri, Barbara; Ceccacci, Francesca; Di Profio, Pietro; Germani, Raimondo; Giansanti, Luisa; Savelli, Gianfranco; Mancini, Giovanna

2012-01-01

The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities. Copyright © 2011 Wiley-Liss, Inc.

Spatial and seasonal factors are key determinants in the aggregation of helminths in their definitive hosts: Pseudamphistomum truncatum in otters (Lutra lutra).

PubMed

Sherrard-Smith, E; Perkins, S E; Chadwick, E A; Cable, J

2015-01-01

Parasites are typically aggregated within their host populations. The most heavily infected hosts are frequently cited as targets for optimal disease control. Yet a heavily infected individual is not necessarily highly infective and does not automatically contribute a higher proportion of infective parasitic stages than a host with fewer parasites. Here, Pseudamphistomum truncatum (Opisthorchiida) parasitic infection within the definitive otter host (Lutra lutra) is used as a model system. The hypothesis tested is that variation in parasite abundance, aggregation and egg production (fecundity, as a proxy of host infectivity) can be explained by abiotic (season and region) or biotic (host age, sex and body condition) factors. Parasite abundance was affected most strongly by the biotic factors of age and body condition, such that adults and otters with a higher condition index had heavier infections than sub-adults or those with a lower condition index, whilst there were no significant differences in parasite abundance among the seasons, regions (ecological regions defined by river catchment boundaries) or host sexes. Conversely, parasite aggregation was affected most strongly by the abiotic factors of season and region, which were supported by four different measures of parasite aggregation (the corrected moment estimate k, Taylor's Power Law, the Index of Discrepancy D, and Boulinier's J). Pseudamphistomum truncatum was highly aggregated within otters, with aggregation stronger in the Midlands (England) and Wales than in the southwestern region of the United Kingdom. Overall, more parasites were found in fewer hosts during the summer, which coincides with the summer peak in parasite fecundity. Combined, these data suggest that (i) few otters carry the majority of P. truncatum parasites and that there are more infective stages (eggs) produced during summer; and (ii) abiotic factors are most influential when describing parasite aggregation whilst biotic factors have

Ultrafast exciton migration in an HJ-aggregate: Potential surfaces and quantum dynamics

NASA Astrophysics Data System (ADS)

Binder, Robert; Polkehn, Matthias; Ma, Tianji; Burghardt, Irene

2017-01-01

Quantum dynamical and electronic structure calculations are combined to investigate the mechanism of exciton migration in an oligothiophene HJ aggregate, i.e., a combination of oligomer chains (J-type aggregates) and stacked aggregates of such chains (H-type aggregates). To this end, a Frenkel exciton model is parametrized by a recently introduced procedure [Binder et al., J. Chem. Phys. 141, 014101 (2014)] which uses oligomer excited-state calculations to perform an exact, point-wise mapping of coupled potential energy surfaces to an effective Frenkel model. Based upon this parametrization, the Multi-Layer Multi-Configuration Time-Dependent Hartree (ML-MCTDH) method is employed to investigate ultrafast dynamics of exciton transfer in a small, asymmetric HJ aggregate model composed of 30 sites and 30 active modes. For a partially delocalized initial condition, it is shown that a torsional defect confines the trapped initial exciton, and planarization induces an ultrafast resonant transition between an HJ-aggregated segment and a covalently bound "dangling chain" end. This model is a minimal realization of experimentally investigated mixed systems exhibiting ultrafast exciton transfer between aggregated, highly planarized chains and neighboring disordered segments.

An Extracellular Serine/Threonine-Rich Protein from Lactobacillus plantarum NCIMB 8826 Is a Novel Aggregation-Promoting Factor with Affinity to Mucin

PubMed Central

Hevia, Arancha; Martínez, Noelia; Ladero, Víctor; Álvarez, Miguel A.; Margolles, Abelardo

2013-01-01

Autoaggregation in lactic acid bacteria is directly related to the production of certain extracellular proteins, notably, aggregation-promoting factors (APFs). Production of aggregation-promoting factors confers beneficial traits to probiotic-producing strains, contributing to their fitness for the intestinal environment. Furthermore, coaggregation with pathogens has been proposed to be a beneficial mechanism in probiotic lactic acid bacteria. This mechanism would limit attachment of the pathogen to the gut mucosa, favoring its removal by the human immune system. In the present paper, we have characterized a novel aggregation-promoting factor in Lactobacillus plantarum. A mutant with a knockout of the D1 gene showed loss of its autoaggregative phenotype and a decreased ability to bind to mucin, indicating an adhesion role of this protein. In addition, heterologous production of the D1 protein or an internal fragment of the protein, characterized by its abundance in serine/threonine, strongly induced autoaggregation in Lactococcus lactis. This result strongly suggested that this internal fragment is responsible for the bioactivity of D1 as an APF. To our knowledge, this is the first report on a gene coding for an aggregation-promoting factor in Lb. plantarum. PMID:23892754

Enterococcus faecalis Ebp pili are important for cell-cell aggregation and intraspecies gene transfer

PubMed Central

Leanti La Rosa, Sabina; Camila Montealegre, Maria; Singh, Kavindra V.

2016-01-01

Enterococcus faecalis is an opportunistic pathogen that ranks among the leading causes of biofilm-associated infections. We previously demonstrated that the endocarditis- and biofilm-associated pili (Ebp) of E. faecalis play a major role in biofilm formation, adherence to abiotic surfaces and experimental infections. In this study, derivatives of E. faecalis strain OG1 were engineered to further characterize functions of Ebp pili. Loss of pili resulted in a 36-fold decrease in the number of closely associated cells when OG1RFΔebpABC was mixed with OG1SSpΔebpABC, compared with mixing the Ebp+ parental strains. In addition, using the Ebp+ parental strains as donor and recipient, we found a statistically significant increase (280–360 %, P < 0.05) in the frequency of plasmid transfer versus using Ebp−  mutants in the conjugation experiments. These results demonstrate a previously unrecognized role of Ebp pili, namely, as important contributors to microscale cell aggregation and horizontal spread of genetic material. PMID:26967674

Multi-factor Effects on the Durability of Recycle Aggregate Concrete

NASA Astrophysics Data System (ADS)

Ma, Huan; Cui, Yu-Li; Zhu, Wen-Yu; Xie, Xian-Jie

2016-05-01

Recycled Aggregate Concrete (RAC) was prepared with different recycled aggregate replacement ratio, 0, 30%, 70% and 100% respectively. The performances of RAC were examined by the freeze-thaw cycle, carbonization and sulfate attack to assess the durability. Results show that test sequence has different effects on the durability of RAC; the durability is poorer when carbonation experiment was carried out firstly, and then other experiment was carried out again; the durability is better when recycled aggregate replacement ratio is 70%.

Reduction in aggregation and energy transfer of quantum dots incorporated in polystyrene beads by kinetic entrapment due to cross-linking during polymerization.

PubMed

Vaidya, Shyam V; Couzis, Alex; Maldarelli, Charles

2015-03-17

We report the development of barcoded polystyrene microbeads, approximately 50 μm in diameter, which are encoded by incorporating multicolored semiconductor fluorescent nanocrystals (quantum dots or QDs) within the microbeads and using the emission spectrum of the embedded QDs as a spectral label. The polymer/nanocrystal bead composites are formed by polymerizing emulsified liquid droplets of styrene monomer and QDs suspended in an immiscible continuous phase (suspension polymerization). We focus specifically on the effect of divinylbenzene (DVB) added to cross-link the linearly growing styrene polymer chains and the effect of this cross-linking on the state of aggregation of the nanocrystals in the composite. Aggregated states of multicolor QDs give rise to nonradiative resonance energy transfer (RET) which distorts the emission label from a spectrum recorded in a reference solvent in which the nanocrystals are well dispersed and unaggregated. A simple barcode is chosen of a mixture of QDs emitting at 560 (yellow) and 620 nm (red). We find that for linear chain growth (no DVB), the QDs aggregate as is evident from the emission spectrum and the QD distribution as seen from confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM) images. Increasing the extent of cross-linking by the addition of DVB is shown to significantly decrease the aggregation and provide a clear label. We suggest that in the absence of cross-linking, linearly growing polymer chains, through enthalpic and entropic effects, drive the nanocrystals into inclusions, while cross-linking kinetically entraps the particle and prevents their aggregation.

Effects of environmental factors on MSP21-25 aggregation indicate the roles of hydrophobic and electrostatic interactions in the aggregation process.

PubMed

Zhang, Xuecheng; Dong, Yuanqiu; Yu, Jigang; Tu, Xiaoming

2014-01-01

Merozoite surface protein 2 (MSP2), one of the most abundant proteins on the merozoite surface of Plasmodium falciparum, is recognized to be important for the parasite's invasion into the host cell and is thus a promising malaria vaccine candidate. However, mediated mainly by its conserved N-terminal 25 residues (MSP21-25), MSP2 readily forms amyloid fibril-like aggregates under physiological conditions in vitro, which impairs its potential as a vaccine component. In addition, there is evidence that MSP2 exists in aggregated forms on the merozoite surface in vivo. To elucidate the aggregation mechanism of MSP21-25 and thereby understand the behavior of MSP2 in vivo and find ways to avoid the aggregation of relevant vaccine in vitro, we investigated the effects of agitation, pH, salts, 1-anilinonaphthalene-8-sulfonic acid (ANS), trimethylamine N-oxide dihydrate (TMAO), urea, and sub-micellar sodium dodecyl sulfate (SDS) on the aggregation kinetics of MSP21-25 using thioflavin T (ThT) fluorescence. The results showed that MSP21-25 aggregation was accelerated by agitation, while repressed by acidic pHs. The salts promoted the aggregation in an anion nature-dependent pattern. Hydrophobic surface-binding agent ANS and detergent urea repressed MSP21-25 aggregation, in contrast to hydrophobic interaction strengthener TMAO, which enhanced the aggregation. Notably, sub-micellar SDS, contrary to its micellar form, promoted MSP21-25 aggregation significantly. Our data indicated that hydrophobic interactions are the predominant driving force of the nucleation of MSP21-25 aggregation, while the elongation is controlled mainly by electrostatic interactions. A kinetic model of MSP21-25 aggregation and its implication were also discussed.

Roles of conformational stability and colloidal stability in the aggregation of recombinant human granulocyte colony-stimulating factor

PubMed Central

Chi, Eva Y.; Krishnan, Sampathkumar; Kendrick, Brent S.; Chang, Byeong S.; Carpenter, John F.; Randolph, Theodore W.

2003-01-01

We studied the non-native aggregation of recombinant human granulocyte stimulating factor (rhGCSF) in solution conditions where native rhGCSF is both conformationally stable compared to its unfolded state and at concentrations well below its solubility limit. Aggregation of rhGCSF first involves the perturbation of its native structure to form a structurally expanded transition state, followed by assembly process to form an irreversible aggregate. The energy barriers of the two steps are reflected in the experimentally measured values of free energy of unfolding (ΔGunf) and osmotic second virial coefficient (B22), respectively. Under solution conditions where rhGCSF conformational stability dominates (i.e., large ΔGunf and negative B22), the first step is rate-limiting, and increasing ΔGunf (e.g., by the addition of sucrose) decreases aggregation. In solutions where colloidal stability is high (i.e., large and positive B22 values) the second step is rate-limiting, and solution conditions (e.g., low pH and low ionic strength) that increase repulsive interactions between protein molecules are effective at reducing aggregation. rhGCSF aggregation is thus controlled by both conformational stability and colloidal stability, and depending on the solution conditions, either could be rate-limiting. PMID:12717013

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.

Peptide adsorption to cyanine dye aggregates revealed by cryo-transmission electron microscopy.

PubMed

von Berlepsch, Hans; Brandenburg, Enrico; Koksch, Beate; Böttcher, Christoph

2010-07-06

The binding interaction between aggregates of the 5-chloro-2-[[5-chloro-3-(3-sulfopropyl)-3H-benzothiazol-2-ylidene]methyl]-3-(3-sulfopropyl)benzothiazolium hydroxide inner salt ammonium salt (CD-1) and alpha-helix, as well as beta-sheet forming de novo designed peptides, was investigated by absorption spectroscopy, circular dichroism spectroscopy, and cryogenic transmission electron microscopy. Both pure dye and pure peptides self-assembled into well-defined supramolecular assemblies in acetate buffer at pH = 4. The dye formed sheetlike and tubular H- and J-aggregates and the peptides alpha-helical coiled-coil assemblies or beta-sheet rich fibrils. After mixing dye and peptide solutions, tubular aggregates with an unusual ultrastructure were found, most likely due to the decoration of dye tubes with monolayers of peptide assemblies based on the strong electrostatic attraction between the oppositely charged species. There was neither indication of a transfer of chirality from the peptides to the dye aggregates nor the opposite effect of a structural transfer from dye aggregates onto the peptides secondary structure.

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

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

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 tomore » 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.« less

Factors That Influence Transfer of Learning from the Online Environment

ERIC Educational Resources Information Center

Everett, Donna R.

2010-01-01

In this paper the author discusses transfer of learning factors to enhance the work skills and knowledge of online MBA students in a managerial communications course. Qualitative research survey methods were utilized; nVivo 8 was used to manipulate the data in two areas: factors that enhance transfer of learning and when students began to apply…

Super-quenched Molecular Probe Based on Aggregation-Induced Emission and Photoinduced Electron Transfer Mechanisms for Formaldehyde Detection in Human Serum.

PubMed

Yang, Haitao; Wang, Fujia; Zheng, Jilin; Lin, Hao; Liu, Bin; Tang, Yi-Da; Zhang, Chong-Jing

2018-06-04

Energy transfer between fluorescent dyes and quenchers is widely used in the design of light-up probes. Although dual quenchers are more effective in offering lower background signals and higher turn-on ratios than one quencher, such probes are less explored in practice as they require both quenchers to be within the proximity of the fluorescent core. In this contribution, we utilized intramolecular motion and photoinduced electron transfer (PET) as quenching mechanisms to build super-quenched light-up probes based on fluorogens with aggregation-induced emission. The optimized light-up probe possesses negligible background and is able to detect not only free formaldehyde (FA) but also polymeric FA, with an unprecedented turn-on ratio of >4900. We envision that this novel dual quenching strategy will help to develop various light-up probes for analyte sensing. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatial Modeling of Iron Transformations Within Artificial Soil Aggregates

NASA Astrophysics Data System (ADS)

Kausch, M.; Meile, C.; Pallud, C.

2008-12-01

Structured soils exhibit significant variations in transport characteristics at the aggregate scale. Preferential flow occurs through macropores while predominantly diffusive exchange takes place in intra-aggregate micropores. Such environments characterized by mass transfer limitations are conducive to the formation of small-scale chemical gradients and promote strong spatial variation in processes controlling the fate of redox-sensitive elements such as Fe. In this study, we present a reactive transport model used to spatially resolve iron bioreductive processes occurring within a spherical aggregate at the interface between advective and diffusive domains. The model is derived from current conceptual models of iron(hydr)oxide (HFO) transformations and constrained by literature and experimental data. Data were obtained from flow-through experiments on artificial soil aggregates inoculated with Shewanella putrefaciens strain CN32, and include the temporal evolution of the bulk solution composition, as well as spatial information on the final solid phase distribution within aggregates. With all iron initially in the form of ferrihydrite, spatially heterogeneous formation of goethite/lepidocrocite, magnetite and siderite was observed during the course of the experiments. These transformations were reproduced by the model, which ascribes a central role to divalent iron as a driver of HFO transformations and master variable in the rate laws of the considered reaction network. The predicted dissolved iron breakthrough curves also match the experimental ones closely. Thus, the computed chemical concentration fields help identify factors governing the observed trends in the solid phase distribution patterns inside the aggregate. Building on a mechanistic description of transformation reactions, fluid flow and solute transport, the model was able to describe the observations and hence illustrates the importance of small-scale gradients and dynamics of bioreductive

Inducing protein aggregation by extensional flow

PubMed Central

Dobson, John; Kumar, Amit; Willis, Leon F.; Tuma, Roman; Higazi, Daniel R.; Turner, Richard; Lowe, David C.; Ashcroft, Alison E.; Radford, Sheena E.; Kapur, Nikil

2017-01-01

Relative to other extrinsic factors, the effects of hydrodynamic flow fields on protein stability and conformation remain poorly understood. Flow-induced protein remodeling and/or aggregation is observed both in Nature and during the large-scale industrial manufacture of proteins. Despite its ubiquity, the relationships between the type and magnitude of hydrodynamic flow, a protein’s structure and stability, and the resultant aggregation propensity are unclear. Here, we assess the effects of a defined and quantified flow field dominated by extensional flow on the aggregation of BSA, β2-microglobulin (β2m), granulocyte colony stimulating factor (G-CSF), and three monoclonal antibodies (mAbs). We show that the device induces protein aggregation after exposure to an extensional flow field for 0.36–1.8 ms, at concentrations as low as 0.5 mg mL−1. In addition, we reveal that the extent of aggregation depends on the applied strain rate and the concentration, structural scaffold, and sequence of the protein. Finally we demonstrate the in situ labeling of a buried cysteine residue in BSA during extensional stress. Together, these data indicate that an extensional flow readily unfolds thermodynamically and kinetically stable proteins, exposing previously sequestered sequences whose aggregation propensity determines the probability and extent of aggregation. PMID:28416674

Effects of Charge-Transfer Excitons on the Photophysics of Organic Semiconductors

NASA Astrophysics Data System (ADS)

Hestand, Nicholas J.

The field of organic electronics has received considerable attention over the past several years due to the promise of novel electronic materials that are cheap, flexible and light weight. While some devices based on organic materials have already emerged on the market (e.g. organic light emitting diodes), a deeper understanding of the excited states within the condensed phase is necessary both to improve current commercial products and to develop new materials for applications that are currently in the commercial pipeline (e.g. organic photovoltaics, wearable displays, and field effect transistors). To this end, a model for pi-conjugated molecular aggregates and crystals is developed and analyzed. The model considers two types of electronic excitations, namely Frenkel and charge-transfer excitons, both of which play a prominent role in determining the nature of the excited states within tightly-packed organic systems. The former consist of an electron-hole pair bound to the same molecule while in the later the electron and hole are located on different molecules. The model also considers the important nuclear reorganization that occurs when the system switches between electronic states. This is achieved using a Holstein-style Hamiltonian that includes linear vibronic coupling of the electronic states to the nuclear motion associated with the high frequency vinyl-stretching and ring-breathing modes. Analysis of the model reveals spectroscopic signatures of charge-transfer mediated J- and H-aggregation in systems where the photophysical properties are determined primarily by charge-transfer interactions. Importantly, such signatures are found to be sensitive to the relative phase of the intermolecular electron and hole transfer integrals, and the relative energy of the Frenkel and charge-transfer states. When the charge-transfer integrals are in phase and the energy of the charge-transfer state is higher than the Frenkel state, the system exhibits J-aggregate

Protein aggregation studied by forward light scattering and light transmission analysis

NASA Astrophysics Data System (ADS)

Penzkofer, A.; Shirdel, J.; Zirak, P.; Breitkreuz, H.; Wolf, E.

2007-12-01

The aggregation of the circadian blue-light photo-receptor cryptochrome from Drosophila melanogaster (dCry) is studied by transmission and forward light scattering measurement in the protein transparent wavelength region. The light scattering in forward direction is caused by Rayleigh scattering which is proportional to the degree of aggregation. The light transmission through the samples in the transparent region is reduced by Mie light scattering in all directions. It depends on the degree of aggregation and the monomer volume fill factor of the aggregates (less total scattering with decreasing monomer volume fill factor of protein globule) allowing a distinction between tightly packed protein aggregation (monomer volume fill factor 1) and loosely packed protein aggregation (monomer volume fill factor less than 1). An increase in aggregation with temperature, concentration, and blue-light exposure is observed. At a temperature of 4 °C and a protein concentration of less than 0.135 mM no dCry aggregation was observed, while at 24 °C and 0.327 mM gelation occurred (loosely packed aggregates occupying the whole solution volume).

Modeling methylene blue aggregation in acidic solution to the limits of factor analysis.

PubMed

Golz, Emily K; Vander Griend, Douglas A

2013-01-15

Methylene blue (MB(+)), a common cationic thiazine dye, aggregates in acidic solutions. Absorbance data for equilibrated solutions of the chloride salt were analyzed over a concentration range of 1.0 × 10(-3) to 2.6 × 10(-5) M, in both 0.1 M HCl and 0.1 M HNO(3). Factor analyses of the raw absorbance data sets (categorically a better choice than effective absorbance) definitively show there are at least three distinct molecular absorbers regardless of acid type. A model with monomer, dimer, and trimer works well, but extensive testing has resulted in several other good models, some with higher order aggregates and some with chloride anions. Good models were frequently indistinguishable from each other by quality of fit or reasonability of molar absorptivity curves. The modeling of simulated data sets demonstrates the cases and degrees to which signal noise in the original data obscure the true model. In particular, the more mathematically similar (less orthogonal) the molar absorptivity curves of the chemical species in a model are, the less signal noise it takes to obscure the true model from other potentially good models. Unfortunately, the molar absorptivity curves in dye aggregation systems like that of methylene blue tend to be sufficiently similar so as to lead to the obscuration of models even at the noise levels (0.0001 ABS) of typical benchtop spectrophotometers.

Geologic and societal factors affecting the international oceanic transport of aggregate

USGS Publications Warehouse

Langer, W.H.

1995-01-01

Crushed stone and sand and gravel are the two main sources of natural aggregate, and together comprise approximately half the volume and tonnage of mined material in the United States. Natural aggregate is a bulky, heavy material without special or unique properties, and it is commonly used near its source of production to minimize haulage cost. However, remoteness is no longer an absolute disqualifier for the production of aggregate. Today interstate aggregate routinely is shipped hundreds of kilometers by rail and barge. In addition, during 1992, the United States imported 1,317,000 metric tons of aggregate from Canada and 1,531,000 metric tons from Mexico. A number of ports on the Atlantic Coast and Gulf Coast of the United States receive imports of crushed stone from foreign sources for transport to various parts of the eastern United States. These areas either lack adequate supplies of aggregate or are augmenting their supplies because they have difficulties meeting current demand. These difficulties may include poor stone quality, environmental permitting problems, or transportation. Certain societal and geologic conditions of New York City and Philadelphia along the Atlantic Coast, and Tampa and New Orleans along the Gulf Coast, are discussed to demonstrate the different combinations of issues that contribute to the economic viability of importing crushed stone. ?? 1995 Oxford University Press.

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.

Hydrogen-bonded aggregates in precise acid copolymers

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

Lueth, Christopher A.; Bolintineanu, Dan S.; Stevens, Mark J., E-mail: msteve@sandia.gov

2014-02-07

We perform atomistic molecular dynamics simulations of melts of four precise acid copolymers, two poly(ethylene-co-acrylic acid) (PEAA) copolymers, and two poly(ethylene-co-sulfonic acid) (PESA) copolymers. The acid groups are spaced by either 9 or 21 carbons along the polymer backbones. Hydrogen bonding causes the acid groups to form aggregates. These aggregates give rise to a low wavevector peak in the structure factors, in agreement with X-ray scattering data for the PEAA materials. The structure factors for the PESA copolymers are very similar to those for the PEAA copolymers, indicating a similar distance between aggregates which depends on the spacer length butmore » not on the nature of the acid group. The PEAA copolymers are found to form more dimers and other small aggregates than do the PESA copolymers, while the PESA copolymers have both more free acid groups and more large aggregates.« less

A Method of Data Aggregation for Wearable Sensor Systems

PubMed Central

Shen, Bo; Fu, Jun-Song

2016-01-01

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

Automated measurement of aggregate indices of shape

DOT National Transportation Integrated Search

1995-12-01

Aggregate angularity is a significant factor in determining pavement resistance to rutting. Determination of aggregate angularity by direct means allows a more meaningful study of the mechanisms of pavement deformation. However, direct techniques hav...

Transfer Factors for Contaminant Uptake by Fruit and Nut Trees

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

Napier, Bruce A.; Fellows, Robert J.; Minc, Leah D.

Transfer of radionuclides from soils into plants is one of the key mechanisms for long-term contamination of the human food chain. Nearly all computer models that address soil-to-plant uptake of radionuclides use empirically-derived transfer factors to address this process. Essentially all available soil-to-plant transfer factors are based on measurements in annual crops. Because very few measurements are available for tree fruits, samples were taken of alfalfa and oats and the stems, leaves, and fruits and nuts of almond, apple, apricot, carob, fig, grape, nectarine, pecan, pistachio (natural and grafted), and pomegranate, along with local surface soil. The samples were dried,more » ground, weighed, and analyzed for trace constituents through a combination of induction-coupled plasma mass spectrometry and instrumental neutron activation analysis for a wide range of naturally-occurring elements. Analysis results are presented and converted to soil-to-plant transfer factors. These are compared to commonly used and internationally recommended values. Those determined for annual crops are very similar to commonly-used values; those determined for tree fruits show interesting differences. Most macro- and micronutrients are slightly reduced in fruits; non-essential elements are reduced further. These findings may be used in existing computer models and may allow development of tree-fruit-specific transfer models.« less

Generation of chimeric minipigs by aggregating 4- to 8-cell-stage blastomeres from somatic cell nuclear transfer with the tracing of enhanced green fluorescent protein.

PubMed

Ji, Huili; Long, Chuan; Feng, Chong; Shi, Ningning; Jiang, Yingdi; Zeng, Guomin; Li, Xirui; Wu, Jingjing; Lu, Lin; Lu, Shengsheng; Pan, Dengke

2017-05-01

Blastocyst complementation is an important technique for generating chimeric organs in organ-deficient pigs, which holds great promise for solving the problem of a shortage of organs for human transplantation procedures. Porcine chimeras have been generated using embryonic germ cells, embryonic stem cells, and induced pluripotent stem cells; however, there are no authentic pluripotent stem cells for pigs. In previous studies, blastomeres from 4- to 8-cell-stage parthenogenetic embryos were able to generate chimeric fetuses efficiently, but the resulting fetuses did not produce live-born young. Here, we used early-stage embryos from somatic cell nuclear transfer (SCNT) to generate chimeric piglets by the aggregation method. Then, the distribution of chimerism in various tissues and organs was observed through the expression of enhanced green fluorescent protein (EGFP). Initially, we determined whether 4- to 8- or 8- to 16-cell-stage embryos were more suitable to generate chimeric piglets. Chimeras were produced by aggregating two EGFP-tagged Wuzhishan minipig (WZSP) SCNT embryos and two Bama minipig (BMP) SCNT embryos. The chimeric piglets were identified by coat color and microsatellite and swine leukocyte antigen analyses. Moreover, the distribution of chimerism in various tissues and organs of the piglets was evaluated by EGFP expression. We found that more aggregated embryos were produced using 4- to 8-cell-stage embryos (157/657, 23.9%) than 8- to 16-cell-stage embryos (100/499, 20.0%). Thus, 4- to 8-cell-stage embryos were used for the generation of chimeras. The rate of blastocysts development after aggregating WZSP with BMP embryos was 50.6%. Transfer of 391 blastocysts developed from 4- to 8-cell-stage embryos to five recipients gave rise to 18 piglets, of which two (11.1%) were confirmed to be chimeric by their coat color and microsatellite examination of the skin. One of the chimeric piglets died at 35 days and was subsequently autopsied, whereas the

Factors affecting the development of somatic cell nuclear transfer embryos in Cattle.

PubMed

Akagi, Satoshi; Matsukawa, Kazutsugu; Takahashi, Seiya

2014-01-01

Nuclear transfer is a complex multistep procedure that includes oocyte maturation, cell cycle synchronization of donor cells, enucleation, cell fusion, oocyte activation and embryo culture. Therefore, many factors are believed to contribute to the success of embryo development following nuclear transfer. Numerous attempts to improve cloning efficiency have been conducted since the birth of the first sheep by somatic cell nuclear transfer. However, the efficiency of somatic cell cloning has remained low, and applications have been limited. In this review, we discuss some of the factors that affect the developmental ability of somatic cell nuclear transfer embryos in cattle.

Factors Affecting the Development of Somatic Cell Nuclear Transfer Embryos in Cattle

PubMed Central

AKAGI, Satoshi; MATSUKAWA, Kazutsugu; TAKAHASHI, Seiya

2014-01-01

Nuclear transfer is a complex multistep procedure that includes oocyte maturation, cell cycle synchronization of donor cells, enucleation, cell fusion, oocyte activation and embryo culture. Therefore, many factors are believed to contribute to the success of embryo development following nuclear transfer. Numerous attempts to improve cloning efficiency have been conducted since the birth of the first sheep by somatic cell nuclear transfer. However, the efficiency of somatic cell cloning has remained low, and applications have been limited. In this review, we discuss some of the factors that affect the developmental ability of somatic cell nuclear transfer embryos in cattle. PMID:25341701

Amyloid-beta aggregation: selective inhibition of aggregation in mixtures of amyloid with different chain lengths.

PubMed Central

Snyder, S W; Ladror, U S; Wade, W S; Wang, G T; Barrett, L W; Matayoshi, E D; Huffaker, H J; Krafft, G A; Holzman, T F

1994-01-01

One of the clinical manifestations of Alzheimer's disease is the deposition of the 39-43 residue amyloid-beta (A beta) peptide in aggregated fibrils in senile plaques. Characterization of the aggregation behavior of A beta is one of the critical issues in understanding the role of A beta in the disease process. Using solution hydrodynamics, A beta was observed to form three types of species in phosphate-buffered saline: insoluble aggregates with sedimentation coefficients of approximately 50,000 S and molecular masses of approximately 10(9) Da, "soluble aggregates" with sedimentation coefficients of approximately 30 S and masses of approximately 10(6) Da, and monomer. When starting from monomer, the aggregation kinetics of A beta 1-40 (A beta 40) and A beta 1-42 (A beta 42), alone and in combination, reveal large differences in the tendency of these peptides to aggregate as a function of pH and other solution conditions. At pH 4.1 and 7.0-7.4, aggregation is significantly slower than at pH 5 and 6. Under all conditions, aggregation of the longer A beta 42 was more rapid than A beta 40. Oxidation of Met-35 to the sulfoxide in A beta 40 enhances the aggregation rate over that of the nonoxidized peptide. Aggregation was found to be dependent upon temperature and to be strongly dependent on peptide concentration and ionic strength, indicating that aggregation is driven by a hydrophobic effect. When A beta 40 and A beta 42 are mixed together, A beta 40 retards the aggregation of A beta 42 in a concentration-dependent manner. Shorter fragments have a decreasing ability to interfere with A beta 42 aggregation. Conversely, the rate of aggregation of A beta 40 can be significantly enhanced by seeding slow aggregating solutions with preformed aggregates of A beta 42. Taken together, the inhibition of A beta 42 aggregation by A beta 40, the seeding of A beta 40 aggregation by A beta 42 aggregates, and the chemical oxidation of A beta 40 suggest that the relative abundance and

Evaluating load transfer restoration, districts 1 and 3

DOT National Transportation Integrated Search

2002-07-01

Since 1950, concrete pavements in California have been constructed without dowel bars in the transverse joints, Consequently, aggregate interlock has been the primary mechanism for load transfer across adjacent slabs. As the pavements age, the aggreg...

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.

Transitioning Transfer Students: Interactive Factors that Influence First-Year Retention

ERIC Educational Resources Information Center

Luo, Mingchu; Williams, James E.; Vieweg, Bruce

2007-01-01

This study examined the diverse patterns of interactive factors that influence transfer students' first-year retention at a midsize four-year university. The population for this study consisted of five cohorts totaling 1,713 full-time, degree-seeking transfer students. Sequential sets of logistic regression analyses on blocks of variables were…

45 CFR 2530.60 - What is the impact of transferring or receiving a transferred education award on an individual's...

Code of Federal Regulations, 2010 CFR

2010-10-01

... does not reduce the aggregate value of education awards the transferring individual is considered to... individual revokes, in whole or in part, a transfer, the value of the education award considered to have been... transferred education award on an individual's eligibility to receive additional education awards? 2530.60...

Optimal policies for aggregate recycling from decommissioned forest roads.

PubMed

Thompson, Matthew; Sessions, John

2008-08-01

To mitigate the adverse environmental impact of forest roads, especially degradation of endangered salmonid habitat, many public and private land managers in the western United States are actively decommissioning roads where practical and affordable. Road decommissioning is associated with reduced long-term environmental impact. When decommissioning a road, it may be possible to recover some aggregate (crushed rock) from the road surface. Aggregate is used on many low volume forest roads to reduce wheel stresses transferred to the subgrade, reduce erosion, reduce maintenance costs, and improve driver comfort. Previous studies have demonstrated the potential for aggregate to be recovered and used elsewhere on the road network, at a reduced cost compared to purchasing aggregate from a quarry. This article investigates the potential for aggregate recycling to provide an economic incentive to decommission additional roads by reducing transport distance and aggregate procurement costs for other actively used roads. Decommissioning additional roads may, in turn, result in improved aquatic habitat. We present real-world examples of aggregate recycling and discuss the advantages of doing so. Further, we present mixed integer formulations to determine optimal levels of aggregate recycling under economic and environmental objectives. Tested on an example road network, incorporation of aggregate recycling demonstrates substantial cost-savings relative to a baseline scenario without recycling, increasing the likelihood of road decommissioning and reduced habitat degradation. We find that aggregate recycling can result in up to 24% in cost savings (economic objective) and up to 890% in additional length of roads decommissioned (environmental objective).

Aggregate complexes of HIV-1 induced by multimeric antibodies.

PubMed

Stieh, Daniel J; King, Deborah F; Klein, Katja; Liu, Pinghuang; Shen, Xiaoying; Hwang, Kwan Ki; Ferrari, Guido; Montefiori, David C; Haynes, Barton; Pitisuttithum, Punnee; Kaewkungwal, Jaranit; Nitayaphan, Sorachai; Rerks-Ngarm, Supachai; Michael, Nelson L; Robb, Merlin L; Kim, Jerome H; Denny, Thomas N; Tomaras, Georgia D; Shattock, Robin J

2014-10-02

Antibody mediated viral aggregation may impede viral transfer across mucosal surfaces by hindering viral movement in mucus, preventing transcytosis, or reducing inter-cellular penetration of epithelia thereby limiting access to susceptible mucosal CD4 T cells and dendritic cells. These functions may work together to provide effective immune exclusion of virus from mucosal tissue; however little is known about the antibody characteristics required to induce HIV aggregation. Such knowledge may be critical to the design of successful immunization strategies to facilitate viral immune exclusion at the mucosal portals of entry. The potential of neutralizing and non-neutralizing IgG and IgA monoclonals (mAbs) to induce HIV-1 aggregation was assessed by Dynamic light scattering (DLS). Although neutralizing and non-neutralizing IgG mAbs and polyclonal HIV-Ig efficiently aggregated soluble Env trimers, they were not capable of forming viral aggregates. In contrast, dimeric (but not monomeric) IgA mAbs induced stable viral aggregate populations that could be separated from uncomplexed virions. Epitope specificity influenced both the degree of aggregation and formation of higher order complexes by dIgA. IgA purified from serum of uninfected RV144 vaccine trial responders were able to efficiently opsonize viral particles in the absence of significant aggregation, reflective of monomeric IgA. These results collectively demonstrate that dIgA is capable of forming stable viral aggregates providing a plausible basis for testing the effectiveness of aggregation as a potential protection mechanism at the mucosal portals of viral entry.

Aggregation effects on anhydrobiotic survival in the tardigrade Richtersius coronifer.

PubMed

Ivarsson, Helen; Jönsson, K Ingemar

2004-02-01

For anhydrobiotic metazoans the rate of desiccation is an important factor influencing the probability of survival in a dry anhydrobiotic state. Formation of animal aggregations, in which the exposed body surface area of individual animals is reduced, represents one way to reduce the rate of evaporation. Such aggregations have earlier been documented in e.g., nematodes. We experimentally evaluate the effect of aggregation size (number of animals in a group of desiccating animals) on anhydrobiotic survival in the eutardigrade Richtersius coronifer. The experiment shows that aggregation provides a clear improvement on anhydrobiotic survival. The most likely explanation for this is that aggregated animals were exposed to a lower rate of desiccation. Although the empirical evidence of aggregation in tardigrades is scarce, our study suggests that aggregation could potentially be an important survival factor for tardigrades living in environments characterized by periods of rapid desiccation. Copyright 2004 Wiley-Liss, Inc.

Synthesis of coupled resonator optical waveguides by cavity aggregation.

PubMed

Muñoz, Pascual; Doménech, José David; Capmany, José

2010-01-18

In this paper, the layer aggregation method is applied to coupled resonator optical waveguides. Starting from the frequency transfer function, the method yields the coupling constants between the resonators. The convergence of the algorithm developed is examined and the related parameters discussed.

Relation of pulmonary vessel size to transfer factor in subjects with airflow obstruction

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

Musk, A.W.

In a group of 61 consecutive patients undergoing assessment of airflow obstruction, a significant linear relation was demonstrated between measurements of the diameter of the midzonal pulmonary vessels on the plain chest radiographs and transfer factor (diffusing capacity for carbon monoxide) (r = 0.46, p < 0.001). Since reduction in transfer factor has been shown to relate to structural emphysema, reduction in midzone vessel caliber implies the same. However, in the individual patient neither the transfer factor nor structural emphysema can be reliably predicted from midzone vessel diameters alone.

Misfolded rhodopsin mutants display variable aggregation properties.

PubMed

Gragg, Megan; Park, Paul S-H

2018-06-08

The largest class of rhodopsin mutations causing autosomal dominant retinitis pigmentosa (adRP) is mutations that lead to misfolding and aggregation of the receptor. The misfolding mutants have been characterized biochemically, and categorized as either partial or complete misfolding mutants. This classification is incomplete and does not provide sufficient information to fully understand the disease pathogenesis and evaluate therapeutic strategies. A Förster resonance energy transfer (FRET) method was utilized to directly assess the aggregation properties of misfolding rhodopsin mutants within the cell. Partial (P23H and P267L) and complete (G188R, H211P, and P267R) misfolding mutants were characterized to reveal variability in aggregation properties. The complete misfolding mutants all behaved similarly, forming aggregates when expressed alone, minimally interacting with the wild-type receptor when coexpressed, and were unresponsive to treatment with the pharmacological chaperone 9-cis retinal. In contrast, variability was observed between the partial misfolding mutants. In the opsin form, the P23H mutant behaved similarly as the complete misfolding mutants. In contrast, the opsin form of the P267L mutant existed as both aggregates and oligomers when expressed alone and formed mostly oligomers with the wild-type receptor when coexpressed. The partial misfolding mutants both reacted similarly to the pharmacological chaperone 9-cis retinal, displaying improved folding and oligomerization when expressed alone but aggregating with wild-type receptor when coexpressed. The observed differences in aggregation properties and effect of 9-cis retinal predict different outcomes in disease pathophysiology and suggest that retinoid-based chaperones will be ineffective or even detrimental. Copyright © 2018 Elsevier B.V. All rights reserved.

Diabatization for Time-Dependent Density Functional Theory: Exciton Transfers and Related Conical Intersections.

PubMed

Tamura, Hiroyuki

2016-11-23

Intermolecular exciton transfers and related conical intersections are analyzed by diabatization for time-dependent density functional theory. The diabatic states are expressed as a linear combination of the adiabatic states so as to emulate the well-defined reference states. The singlet exciton coupling calculated by the diabatization scheme includes contributions from the Coulomb (Förster) and electron exchange (Dexter) couplings. For triplet exciton transfers, the Dexter coupling, charge transfer integral, and diabatic potentials of stacked molecules are calculated for analyzing direct and superexchange pathways. We discuss some topologies of molecular aggregates that induce conical intersections on the vanishing points of the exciton coupling, namely boundary of H- and J-aggregates and T-shape aggregates, as well as canceled exciton coupling to the bright state of H-aggregate, i.e., selective exciton transfer to the dark state. The diabatization scheme automatically accounts for the Berry phase by fixing the signs of reference states while scanning the coordinates.

Apple Procyanidins Suppress Amyloid β-Protein Aggregation

PubMed Central

Toda, Toshihiko; Sunagawa, Tadahiro; Kanda, Tomomasa; Tagashira, Motoyuki; Shirasawa, Takuji; Shimizu, Takahiko

2011-01-01

Procyanidins (PCs) are major components of the apple polyphenols (APs). We previously reported that treatment with PC extended the mean lifespan of Caenorhabditis elegans (Sunagawa et al., 2011). In order to estimate the neuroprotective effects of PC, we investigated the antiaggregative activity of PC on amyloid β-protein (Aβ) aggregation, which is a pathological hallmark of Alzheimer's disease. We herein report that PC significantly suppressed Aβ42 aggregation and dissociated Aβ42 aggregates in a dose-dependent manner, indicating that PC is a potent suppressor of Aβ aggregation. Furthermore, PC significantly inhibited Aβ42 neurotoxicity and stimulated proliferation in PC-12 cells. These results suggested that the PC and AP acted as neuroprotective factors against toxic Aβ aggregates. PMID:21826271

On the accuracy of the LSC-IVR approach for excitation energy transfer in molecular aggregates

NASA Astrophysics Data System (ADS)

Teh, Hung-Hsuan; Cheng, Yuan-Chung

2017-04-01

We investigate the applicability of the linearized semiclassical initial value representation (LSC-IVR) method to excitation energy transfer (EET) problems in molecular aggregates by simulating the EET dynamics of a dimer model in a wide range of parameter regime and comparing the results to those obtained from a numerically exact method. It is found that the LSC-IVR approach yields accurate population relaxation rates and decoherence rates in a broad parameter regime. However, the classical approximation imposed by the LSC-IVR method does not satisfy the detailed balance condition, generally leading to incorrect equilibrium populations. Based on this observation, we propose a post-processing algorithm to solve the long time equilibrium problem and demonstrate that this long-time correction method successfully removed the deviations from exact results for the LSC-IVR method in all of the regimes studied in this work. Finally, we apply the LSC-IVR method to simulate EET dynamics in the photosynthetic Fenna-Matthews-Olson complex system, demonstrating that the LSC-IVR method with long-time correction provides excellent description of coherent EET dynamics in this typical photosynthetic pigment-protein complex.

The Rejuvenating Effect in Hot Asphalt Recycling by Mortar Transfer Ratio and Image Analysis

PubMed Central

Wang, Fusong; Wang, Zipeng; Li, Chao; Xiao, Yue; Wu, Shaopeng; Pan, Pan

2017-01-01

Using a rejuvenator to improve the performance of asphalt pavement is an effective and economic way of hot asphalt recycling. This research analyzes the rejuvenating effect on aged asphalt by means of a Mortar Transfer Ratio (MTR) test, which concerns the ratio of asphalt mortar that moves from recycled aggregates (RAP aggregates) to fresh added aggregates when aged asphalt is treated with a regenerating agent and comes into contact with fresh aggregates. The proposed MTR test analyzes the regeneration in terms of the softening degree on aged asphalt when the rejuvenator is applied. The covered area ratio is studied with an image analyzing tool to understand the possibility of mortar transferring from RAP aggregates to fresh aggregates. Additionally, a micro-crack closure test is conducted and observed through a microscope. The repairing ability and diffusion characteristics of micro-cracks can therefore be analyzed. The test results demonstrate that the proposed mortar transfer ratio is a feasible way to evaluate rejuvenator diffusion during hot recycling. The mortar transfer ratio and uncovered area ratio on fresh aggregates are compatible, and can be used to quantify the contribution of the rejuvenator. Within a certain temperature range, the diffusing effect of the rejuvenator is better when the diffusing temperature is higher. The diffusion time of the rejuvenator is optimum when diffusion occurs for 4–8 h. When the rejuvenator is properly applied, the rough and cracking surface can be repaired, resulting in better covered aggregates. The micro-closure analysis visually indicates that rejuvenators can be used to repair the RAP aggregates during hot recycling. PMID:28772935

The Rejuvenating Effect in Hot Asphalt Recycling by Mortar Transfer Ratio and Image Analysis.

PubMed

Wang, Fusong; Wang, Zipeng; Li, Chao; Xiao, Yue; Wu, Shaopeng; Pan, Pan

2017-05-24

Using a rejuvenator to improve the performance of asphalt pavement is an effective and economic way of hot asphalt recycling. This research analyzes the rejuvenating effect on aged asphalt by means of a Mortar Transfer Ratio (MTR) test, which concerns the ratio of asphalt mortar that moves from recycled aggregates (RAP aggregates) to fresh added aggregates when aged asphalt is treated with a regenerating agent and comes into contact with fresh aggregates. The proposed MTR test analyzes the regeneration in terms of the softening degree on aged asphalt when the rejuvenator is applied. The covered area ratio is studied with an image analyzing tool to understand the possibility of mortar transferring from RAP aggregates to fresh aggregates. Additionally, a micro-crack closure test is conducted and observed through a microscope. The repairing ability and diffusion characteristics of micro-cracks can therefore be analyzed. The test results demonstrate that the proposed mortar transfer ratio is a feasible way to evaluate rejuvenator diffusion during hot recycling. The mortar transfer ratio and uncovered area ratio on fresh aggregates are compatible, and can be used to quantify the contribution of the rejuvenator. Within a certain temperature range, the diffusing effect of the rejuvenator is better when the diffusing temperature is higher. The diffusion time of the rejuvenator is optimum when diffusion occurs for 4-8 h. When the rejuvenator is properly applied, the rough and cracking surface can be repaired, resulting in better covered aggregates. The micro-closure analysis visually indicates that rejuvenators can be used to repair the RAP aggregates during hot recycling.

Origin and Evolution of the Sponge Aggregation Factor Gene Family

PubMed Central

Grice, Laura F.; Gauthier, Marie E.A.; Roper, Kathrein E.; Fernàndez-Busquets, Xavier; Degnan, Sandie M.

2017-01-01

Although discriminating self from nonself is a cardinal animal trait, metazoan allorecognition genes do not appear to be homologous. Here, we characterize the Aggregation Factor (AF) gene family, which encodes putative allorecognition factors in the demosponge Amphimedon queenslandica, and trace its evolution across 24 sponge (Porifera) species. The AF locus in Amphimedon is comprised of a cluster of five similar genes that encode Calx-beta and Von Willebrand domains and a newly defined Wreath domain, and are highly polymorphic. Further AF variance appears to be generated through individualistic patterns of RNA editing. The AF gene family varies between poriferans, with protein sequences and domains diagnostic of the AF family being present in Amphimedon and other demosponges, but absent from other sponge classes. Within the demosponges, AFs vary widely with no two species having the same AF repertoire or domain organization. The evolution of AFs suggests that their diversification occurs via high allelism, and the continual and rapid gain, loss and shuffling of domains over evolutionary time. Given the marked differences in metazoan allorecognition genes, we propose the rapid evolution of AFs in sponges provides a model for understanding the extensive diversification of self–nonself recognition systems in the animal kingdom. PMID:28104746

A conceptual framework for transferring research to practice.

PubMed

Simpson, D Dwayne

2002-06-01

Systematic evaluations of efforts to transfer research-based interventions and procedures into general practice at community drug treatment programs have been limited. However, practical experiences as well as results from studies of technology transfer and organizational behavior in related fields provide a basis for proposing a heuristic model of key factors that influence this process. The successful completion of four stages of activity typically involved in program change (exposure, adoption, implementation, and practice of new interventions) appears to be influenced by several organizational considerations (e.g., institutional readiness for change, resources, and climate) as well as staff attributes. Assessment instruments for measuring organizational functioning (based on ratings aggregated for staff and patients in a program) are introduced, along with preliminary evidence for their validity. A better conceptual understanding of the process of program change and common barriers that may be encountered is needed for effectively transferring research to practice.

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.

Two cell-counting factors regulate the aggregate size of the cellular slime mold Dictyostelium discoideum.

PubMed

Okuwa, T; Katayama, T; Takano, A; Kodaira, K; Yasukawa, H

2001-12-01

Countin, a cell-counting factor in Dictyostelium discoideum, is considered to limit the maximum size of the multicellular structure, because a countin null strain forms a huge fruiting body compared to that of the wild-type. A novel gene, countin2, that is highly homologous to countin (40% identity in amino acid sequence) was identified in the D. discoideum genome. The countin2 null strain formed a 1.7-fold higher number of the aggregates, resulting in smaller fruiting bodies compared with those of wild-type cells. Thus, the Countin2 protein is thought to limit the minimum size of the multicellular structure. The size and number of aggregates formed by a mixture of countin null and countin2 null strains were the same as those of the wild-type. These findings demonstrate that a combination of Countin and Countin2 proteins determines the appropriate size of the multicellular structure of D. discoideum.

The "polyenviromic risk score": Aggregating environmental risk factors predicts conversion to psychosis in familial high-risk subjects.

PubMed

Padmanabhan, Jaya L; Shah, Jai L; Tandon, Neeraj; Keshavan, Matcheri S

2017-03-01

Young relatives of individuals with schizophrenia (i.e. youth at familial high-risk, FHR) are at increased risk of developing psychotic disorders, and show higher rates of psychiatric symptoms, cognitive and neurobiological abnormalities than non-relatives. It is not known whether overall exposure to environmental risk factors increases risk of conversion to psychosis in FHR subjects. Subjects consisted of a pilot longitudinal sample of 83 young FHR subjects. As a proof of principle, we examined whether an aggregate score of exposure to environmental risk factors, which we term a 'polyenviromic risk score' (PERS), could predict conversion to psychosis. The PERS combines known environmental risk factors including cannabis use, urbanicity, season of birth, paternal age, obstetric and perinatal complications, and various types of childhood adversity, each weighted by its odds ratio for association with psychosis in the literature. A higher PERS was significantly associated with conversion to psychosis in young, familial high-risk subjects (OR=1.97, p=0.009). A model combining the PERS and clinical predictors had a sensitivity of 27% and specificity of 96%. An aggregate index of environmental risk may help predict conversion to psychosis in FHR subjects. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantitative imaging of aggregated emulsions.

PubMed

Penfold, Robert; Watson, Andrew D; Mackie, Alan R; Hibberd, David J

2006-02-28

Noise reduction, restoration, and segmentation methods are developed for the quantitative structural analysis in three dimensions of aggregated oil-in-water emulsion systems imaged by fluorescence confocal laser scanning microscopy. Mindful of typical industrial formulations, the methods are demonstrated for concentrated (30% volume fraction) and polydisperse emulsions. Following a regularized deconvolution step using an analytic optical transfer function and appropriate binary thresholding, novel application of the Euclidean distance map provides effective discrimination of closely clustered emulsion droplets with size variation over at least 1 order of magnitude. The a priori assumption of spherical nonintersecting objects provides crucial information to combat the ill-posed inverse problem presented by locating individual particles. Position coordinates and size estimates are recovered with sufficient precision to permit quantitative study of static geometrical features. In particular, aggregate morphology is characterized by a novel void distribution measure based on the generalized Apollonius problem. This is also compared with conventional Voronoi/Delauney analysis.

Coherent and incoherent ultrasound backscatter from cell aggregates.

PubMed

de Monchy, Romain; Destrempes, François; Saha, Ratan K; Cloutier, Guy; Franceschini, Emilie

2016-09-01

The effective medium theory (EMT) was recently developed to model the ultrasound backscatter from aggregating red blood cells [Franceschini, Metzger, and Cloutier, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 58, 2668-2679 (2011)]. The EMT assumes that aggregates can be treated as homogeneous effective scatterers, which have effective properties determined by the aggregate compactness and the acoustical characteristics of the cells and the surrounding medium. In this study, the EMT is further developed to decompose the differential backscattering cross section of a single cell aggregate into coherent and incoherent components. The coherent component corresponds to the squared norm of the average scattering amplitude from the effective scatterer, and the incoherent component considers the variance of the scattering amplitude (i.e., the mean squared norm of the fluctuation of the scattering amplitude around its mean) within the effective scatterer. A theoretical expression for the incoherent component based on the structure factor is proposed and compared with another formulation based on the Gaussian direct correlation function. This theoretical improvement is assessed using computer simulations of ultrasound backscatter from aggregating cells. The consideration of the incoherent component based on the structure factor allows us to approximate the simulations satisfactorily for a product of the wavenumber times the aggregate radius kr ag around 2.

Direct factor IXa inhibition with the RNA-aptamer pegnivacogin reduces platelet reactivity in vitro and residual platelet aggregation in patients with acute coronary syndromes.

PubMed

Staudacher, Dawid L; Putz, Vera; Heger, Lukas; Reinöhl, Jochen; Hortmann, Marcus; Zelenkofske, Steven L; Becker, Richard C; Rusconi, Christopher P; Bode, Christoph; Ahrens, Ingo

2017-04-01

Residual platelet reactivity is a predictor of poor prognosis in patients with acute coronary syndromes (ACSs) undergoing percutaneous coronary intervention. Thrombin is a major platelet activator and upon initiation of the coagulation cascade, it is subsequently produced downstream of factor IXa, which itself is known to be increased in ACS. Pegnivacogin is a novel RNA-aptamer based factor IXa inhibitor featuring a reversal agent, anivamersen. We hypothesized that pegnivacogin could reduce platelet reactivity. Whole blood samples from healthy volunteers were incubated in vitro in the presence and absence of pegnivacogin and platelet reactivity was analysed. In addition, platelet aggregometry was performed in blood samples from ACS patients in the RADAR trial featuring the intravenous administration of pegnivacogin as well as reversal by anivamersen. In vitro, pegnivacogin significantly reduced adenosine diphosphate-induced CD62P-expression (100% vs. 89.79±4.04%, p=0.027, n=9) and PAC-1 binding (100% vs. 83.02±4.08%, p=0.010, n=11). Platelet aggregation was reduced (97.71±5.30% vs. 66.53±9.92%, p=0.013, n=10) as evaluated by light transmission aggregometry. In the presence of the RNA-aptamer reversal agent anivamersen, neither CD62P-expression nor platelet aggregation was attenuated. In patients with ACS treated with aspirin and clopidogrel, residual platelet aggregation was significantly reduced 20 min after intravenous bolus of 1 mg/kg pegnivacogin (100% versus 43.21±8.23%, p=0.020). Inhibition of factor IXa by pegnivacogin decreases platelet activation and aggregation in vitro. This effect was negated by anivamersen. In ACS patients, platelet aggregation was significantly reduced after intravenous pegnivacogin. An aptamer-based anticoagulant inhibiting factor IXa therefore might be a promising antithrombotic strategy in ACS patients.

Aggregate Exposure and Cumulative Risk Assessment—Integrating Occupational and Non-occupational Risk Factors

PubMed Central

Lentz, T. J.; Dotson, G. S.; Williams, P. R.D.; Maier, A.; Gadagbui, B.; Pandalai, S. P.; Lamba, A.; Hearl, F.; Mumtaz, M.

2015-01-01

Occupational exposure limits have traditionally focused on preventing morbidity and mortality arising from inhalation exposures to individual chemical stressors in the workplace. While central to occupational risk assessment, occupational exposure limits have limited application as a refined disease prevention tool because they do not account for all of the complexities of the work and non-occupational environments and are based on varying health endpoints. To be of greater utility, occupational exposure limits and other risk management tools could integrate broader consideration of risks from multiple exposure pathways and routes (aggregate risk) as well as the combined risk from exposure to both chemical and non-chemical stressors, within and beyond the workplace, including the possibility that such exposures may cause interactions or modify the toxic effects observed (cumulative risk). Although still at a rudimentary stage in many cases, a variety of methods and tools have been developed or are being used in allied risk assessment fields to incorporate such considerations in the risk assessment process. These approaches, which are collectively referred to as cumulative risk assessment, have potential to be adapted or modified for occupational scenarios and provide a tangible path forward for occupational risk assessment. Accounting for complex exposures in the workplace and the broader risks faced by the individual also requires a more complete consideration of the composite effects of occupational and non-occupational risk factors to fully assess and manage worker health problems. Barriers to integrating these different factors remain, but new and ongoing community-based and worker health-related initiatives may provide mechanisms for identifying and integrating risk from aggregate exposures and cumulative risks from all relevant sources, be they occupational or non-occupational. PMID:26583907

Aggregate Exposure and Cumulative Risk Assessment--Integrating Occupational and Non-occupational Risk Factors.

PubMed

Lentz, T J; Dotson, G S; Williams, P R D; Maier, A; Gadagbui, B; Pandalai, S P; Lamba, A; Hearl, F; Mumtaz, M

2015-01-01

Occupational exposure limits have traditionally focused on preventing morbidity and mortality arising from inhalation exposures to individual chemical stressors in the workplace. While central to occupational risk assessment, occupational exposure limits have limited application as a refined disease prevention tool because they do not account for all of the complexities of the work and non-occupational environments and are based on varying health endpoints. To be of greater utility, occupational exposure limits and other risk management tools could integrate broader consideration of risks from multiple exposure pathways and routes (aggregate risk) as well as the combined risk from exposure to both chemical and non-chemical stressors, within and beyond the workplace, including the possibility that such exposures may cause interactions or modify the toxic effects observed (cumulative risk). Although still at a rudimentary stage in many cases, a variety of methods and tools have been developed or are being used in allied risk assessment fields to incorporate such considerations in the risk assessment process. These approaches, which are collectively referred to as cumulative risk assessment, have potential to be adapted or modified for occupational scenarios and provide a tangible path forward for occupational risk assessment. Accounting for complex exposures in the workplace and the broader risks faced by the individual also requires a more complete consideration of the composite effects of occupational and non-occupational risk factors to fully assess and manage worker health problems. Barriers to integrating these different factors remain, but new and ongoing community-based and worker health-related initiatives may provide mechanisms for identifying and integrating risk from aggregate exposures and cumulative risks from all relevant sources, be they occupational or non-occupational.

Protein aggregation and misfolding: good or evil?

NASA Astrophysics Data System (ADS)

Pastore, Annalisa; Temussi, Pierandrea

2012-06-01

Protein aggregation and misfolding have important implications in an increasing number of fields ranging from medicine to biology to nanotechnology and material science. The interest in understanding this field has accordingly increased steadily over the last two decades. During this time the number of publications that have been dedicated to protein aggregation has increased exponentially, tackling the problem from several different and sometime contradictory perspectives. This review is meant to summarize some of the highlights that come from these studies and introduce this topical issue on the subject. The factors that make a protein aggregate and the cellular strategies that defend from aggregation are discussed together with the perspectives that the accumulated knowledge may open.

Protein aggregation and misfolding: good or evil?

PubMed

Pastore, Annalisa; Temussi, Pierandrea

2012-06-20

Protein aggregation and misfolding have important implications in an increasing number of fields ranging from medicine to biology to nanotechnology and material science. The interest in understanding this field has accordingly increased steadily over the last two decades. During this time the number of publications that have been dedicated to protein aggregation has increased exponentially, tackling the problem from several different and sometime contradictory perspectives. This review is meant to summarize some of the highlights that come from these studies and introduce this topical issue on the subject. The factors that make a protein aggregate and the cellular strategies that defend from aggregation are discussed together with the perspectives that the accumulated knowledge may open.

Interactions between extracellular polymeric substances and clay minerals affect soil aggregation

NASA Astrophysics Data System (ADS)

Vogel, Cordula; Rehschuh, Stephanie; Kemi Olagoke, Folasade; Redmile Gordon, Marc; Kalbiltz, Karsten

2017-04-01

Soil aggregation is crucial for carbon (C) sequestration and microbial processes have been recognised as important control of aggregate turnover (formation, stability, and destruction). However, how microorganisms contribute to these processes is still a matter of debate. An enthralling mechanism determining aggregate turnover and therefore C sequestration may be the excretion of extracellular polymeric substances (EPS) as microbial glue, but effects of EPS on aggregation is largely unknown. Moreover, interdependencies between important aggregation factors like the amount of fine-sized particles (clay content), the decomposability of organic matter and the microbial community (size and composition, as well as the excretion of EPS) are still poorly understood. Therefore, we studied the complex interactions between these factors and their role in aggregate turnover. It was hypothesized that an increase in microbial activity, induced by the input of organic substrates, will stimulate EPS production and therefore the formation and stability of aggregates. To test this hypothesis, an incubation experiment has been conducted across a gradient of clay content (montmorillonite) and substrate decomposability (starch and glucose) as main drivers of the microbial activity. A combination of aggregate separation and stability tests were applied. This results will be examined with respect to the obtained microbial parameters (amount and composition of EPS, CO2 emission, microbial biomass, phospholipid fatty acid), to disentangle the mechanisms and factors controlling aggregate turnover affected by soil microorganisms. This study is expected to provide insights on the role of EPS in the stability of aggregates. Thus, the results of this study will provide an improved understanding of the underlying processes of aggregate turnover in soils, which is necessary to implement strategies for enhanced C sequestration in agricultural soils.

Plasmon enhanced fluorescence with aggregated shell-isolated nanoparticles.

PubMed

Osorio-Román, Igor O; Guerrero, Ariel R; Albella, Pablo; Aroca, Ricardo F

2014-10-21

Shell-isolated nanoparticles (SHINs) nanostructures provide a versatile substrate where the localized surface plasmon resonances (LSPRs) are well-defined. For SHINEF, the silver (or gold) metal core is protected by the SiO2 coating, which is thicker than the critical distance for minimum quenching by the metal. In the present work, it is shown that an increase in the SHINEF enhancement factor may be achieved by inducing SHIN aggregation with electrolytes in solution. The proof of concept is demonstrated using NaCl as aggregating agent, although other inorganic salts will also aggregate SHIN nanoparticles. As much as a 10-fold enhancement in the SHINEF enhancement factor (EF) may be achieved by tuning the electrolyte concentrations in solution. The SHINEF experiments include the study of the aggregation effect controlling gold SHIN's surface concentration via spraying. Au-SHINs are sprayed onto layer-by-layer (LbL) and Langmuir-Blodgett (LB) films, and samples are fabricated using fluorophores with low and also high quantum yield.

Equine cloning: in vitro and in vivo development of aggregated embryos.

PubMed

Gambini, Andrés; Jarazo, Javier; Olivera, Ramiro; Salamone, Daniel F

2012-07-01

The production of cloned equine embryos remains highly inefficient. Embryo aggregation has not yet been tested in the equine, and it might represent an interesting strategy to improve embryo development. This study evaluated the effect of cloned embryo aggregation on in vitro and in vivo equine embryo development. Zona-free reconstructed embryos were individually cultured in microwells (nonaggregated group) or as 2- or 3-embryo aggregates (aggregated groups). For in vitro development, they were cultured until blastocyst stage and then either fixed for Oct-4 immunocytochemical staining or maintained in in vitro culture where blastocyst expansion was measured daily until Day 17 or the day on which they collapsed. For in vivo assays, Day 7-8 blastocysts were transferred to synchronized mares and resultant vesicles, and cloned embryos were measured by ultrasonography. Embryo aggregation improved blastocyst rates on a per well basis, and aggregation did not imply additional oocytes to obtain blastocysts. Embryo aggregation improved embryo quality, nevertheless it did not affect Day 8 and Day 16 blastocyst Oct-4 expression patterns. Equine cloned blastocysts expanded and increased their cell numbers when they were maintained in in vitro culture, describing a particular pattern of embryo growth that was unexpectedly independent of embryo aggregation, as all embryos reached similar size after Day 7. Early pregnancy rates were higher using blastocysts derived from aggregated embryos, and advanced pregnancies as live healthy foals also resulted from aggregated embryos. These results indicate that the strategy of aggregating embryos can improve their development, supporting the establishment of equine cloned pregnancies.

Extracting Spectroscopic Factors of Argon Isotopes from Transfer Reactions

NASA Astrophysics Data System (ADS)

Manfredi, Juan; Lee, J.; Tsang, M. B.; Lynch, W. G.; Barney, J.; Estee, J.; Sweany, S.; Brown, K. W.; Cerizza, G.; Anderson, C.; Setiawan, H.; Loelius, C.; Xu, Z.; Rogers, A. M.; Pruitt, C.; Sobotka, L. G.; Elson, J. M.; Langer, C.; Chajecki, Z.; Chen, G.; Jones, K. L.; Smith, K.; Xiao, Z.; Li, Z.; Winkelbauer, J. R.

2017-01-01

A spectroscopic factor (SF) quantifies the single particle occupancy of a given state in a nucleus. For the argon isotopes, there is a discrepancy of the SF between studies that use transfer reactions and knockout reactions. Understanding the SFs of these isotopes, and in particular how the SF changes across the isotopic chain, is important for understanding how single particle structure changes with neutron number. The transfer reactions 34Ar(p,d) and 46Ar(p,d) were measured at the National Superconducting Cyclotron Laboratory (NSCL) using the same beam energy (70 MeV/u) as from the previous knockout measurement. Spectroscopic factors were extracted from measured angular distributions via ADWA calculations. Preliminary findings will be presented. The National Superconducting Cyclotron Laboratory is supported by the NSF (PHY 1102511), and Juan Manfredi is supported by the DOE NNSA Stewardship Science Graduate Fellowship.

Origin and Evolution of the Sponge Aggregation Factor Gene Family.

PubMed

Grice, Laura F; Gauthier, Marie E A; Roper, Kathrein E; Fernàndez-Busquets, Xavier; Degnan, Sandie M; Degnan, Bernard M

2017-05-01

Although discriminating self from nonself is a cardinal animal trait, metazoan allorecognition genes do not appear to be homologous. Here, we characterize the Aggregation Factor (AF) gene family, which encodes putative allorecognition factors in the demosponge Amphimedon queenslandica, and trace its evolution across 24 sponge (Porifera) species. The AF locus in Amphimedon is comprised of a cluster of five similar genes that encode Calx-beta and Von Willebrand domains and a newly defined Wreath domain, and are highly polymorphic. Further AF variance appears to be generated through individualistic patterns of RNA editing. The AF gene family varies between poriferans, with protein sequences and domains diagnostic of the AF family being present in Amphimedon and other demosponges, but absent from other sponge classes. Within the demosponges, AFs vary widely with no two species having the same AF repertoire or domain organization. The evolution of AFs suggests that their diversification occurs via high allelism, and the continual and rapid gain, loss and shuffling of domains over evolutionary time. Given the marked differences in metazoan allorecognition genes, we propose the rapid evolution of AFs in sponges provides a model for understanding the extensive diversification of self-nonself recognition systems in the animal kingdom. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Exciton-Exciton Annihilation as a Probe of Interchain Interactions in PPV-Oligomer Aggregates.

PubMed

Peteanu, Linda A; Chowdhury, Sanchari; Wildeman, Jurjen; Sfeir, Matthew Y

2017-02-23

One measure of exciton mobility in an aggregate is the efficiency of exciton-exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH-PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed from the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. The wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.

Block-accelerated aggregation multigrid for Markov chains with application to PageRank problems

NASA Astrophysics Data System (ADS)

Shen, Zhao-Li; Huang, Ting-Zhu; Carpentieri, Bruno; Wen, Chun; Gu, Xian-Ming

2018-06-01

Recently, the adaptive algebraic aggregation multigrid method has been proposed for computing stationary distributions of Markov chains. This method updates aggregates on every iterative cycle to keep high accuracies of coarse-level corrections. Accordingly, its fast convergence rate is well guaranteed, but often a large proportion of time is cost by aggregation processes. In this paper, we show that the aggregates on each level in this method can be utilized to transfer the probability equation of that level into a block linear system. Then we propose a Block-Jacobi relaxation that deals with the block system on each level to smooth error. Some theoretical analysis of this technique is presented, meanwhile it is also adapted to solve PageRank problems. The purpose of this technique is to accelerate the adaptive aggregation multigrid method and its variants for solving Markov chains and PageRank problems. It also attempts to shed some light on new solutions for making aggregation processes more cost-effective for aggregation multigrid methods. Numerical experiments are presented to illustrate the effectiveness of this technique.

Modeling the impact of soil aggregate size on selenium immobilization

NASA Astrophysics Data System (ADS)

Kausch, M. F.; Pallud, C. E.

2013-03-01

Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se) mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI), and selenite, Se(IV), can be microbially reduced to solid, elemental Se, Se(0), and anoxic microzones within soil aggregates are thought to promote this process in otherwise well-aerated soils. To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm) made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI) via Se(IV) to Se(0). Aggregates were surrounded by a constant flow providing Se(VI) and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se species. The spatial and temporal dynamics of the model were validated with data from experiments, and predictive simulations were performed covering aggregate sizes 1-2.5 cm in diameter. Simulations predict that selenium retention scales with aggregate size. Depending on O2, Se(VI), and pyruvate concentrations, selenium retention was 4-23 times higher in 2.5 cm aggregates compared to 1 cm aggregates. Under oxic conditions, aggregate size and pyruvate concentrations were found to have a positive synergistic effect on selenium retention. Promoting soil aggregation on

Modeling the impact of soil aggregate size on selenium immobilization

NASA Astrophysics Data System (ADS)

Kausch, M. F.; Pallud, C. E.

2012-09-01

Soil aggregates are mm- to cm-sized microporous structures separated by macropores. Whereas fast advective transport prevails in macropores, advection is inhibited by the low permeability of intra-aggregate micropores. This can lead to mass transfer limitations and the formation of aggregate-scale concentration gradients affecting the distribution and transport of redox sensitive elements. Selenium (Se) mobilized through irrigation of seleniferous soils has emerged as a major aquatic contaminant. In the absence of oxygen, the bioavailable oxyanions selenate, Se(VI), and selenite, Se(IV), can be microbially reduced to solid, elemental Se, Se(0), and anoxic microzones within soil aggregates are thought to promote this process in otherwise well aerated soils. To evaluate the impact of soil aggregate size on selenium retention, we developed a dynamic 2-D reactive transport model of selenium cycling in a single idealized aggregate surrounded by a macropore. The model was developed based on flow-through-reactor experiments involving artificial soil aggregates (diameter: 2.5 cm) made of sand and containing Enterobacter cloacae SLD1a-1 that reduces Se(VI) via Se(IV) to Se(0). Aggregates were surrounded by a constant flow providing Se(VI) and pyruvate under oxic or anoxic conditions. In the model, reactions were implemented with double-Monod rate equations coupled to the transport of pyruvate, O2, and Se-species. The spatial and temporal dynamics of the model were validated with data from experiments and predictive simulations were performed covering aggregate sizes between 1 and 2.5 cm diameter. Simulations predict that selenium retention scales with aggregate size. Depending on O2, Se(VI), and pyruvate concentrations, selenium retention was 4-23 times higher in 2.5-cm-aggregates compared to 1-cm-aggregates. Under oxic conditions, aggregate size and pyruvate-concentrations were found to have a positive synergistic effect on selenium retention. Promoting soil aggregation on

Influence of indoor environmental factors on mass transfer parameters and concentrations of semi-volatile organic compounds.

PubMed

Wei, Wenjuan; Mandin, Corinne; Ramalho, Olivier

2018-03-01

Semi-volatile organic compounds (SVOCs) in indoor environments can partition among the gas phase, airborne particles, settled dust, and available surfaces. The mass transfer parameters of SVOCs, such as the mass transfer coefficient and the partition coefficient, are influenced by indoor environmental factors. Subsequently, indoor SVOC concentrations and thus occupant exposure can vary depending on environmental factors. In this review, the influence of six environmental factors, i.e., indoor temperature, humidity, ventilation, airborne particle concentration, source loading factor, and reactive chemistry, on the mass transfer parameters and indoor concentrations of SVOCs was analyzed and tentatively quantified. The results show that all mass transfer parameters vary depending on environmental factors. These variations are mostly characterized by empirical equations, particularly for humidity. Theoretical calculations of these parameters based on mass transfer mechanisms are available only for the emission of SVOCs from source surfaces when airborne particles are not present. All mass transfer parameters depend on the temperature. Humidity influences the partition of SVOCs among different phases and is associated with phthalate hydrolysis. Ventilation has a combined effect with the airborne particle concentration on SVOC emission and their mass transfer among different phases. Indoor chemical reactions can produce or eliminate SVOCs slowly. To better model the dynamic SVOC concentration indoors, the present review suggests studying the combined effect of environmental factors in real indoor environments. Moreover, interactions between indoor environmental factors and human activities and their influence on SVOC mass transfer processes should be considered. Copyright © 2017 Elsevier Ltd. All rights reserved.

Soils as sediment: does aggregation skew slope scale SOC balances?

NASA Astrophysics Data System (ADS)

Hu, Yaxian; Fister, Wolfgang; Kuhn, Nikolaus

2014-05-01

The net effect of soil erosion as a source or sink of CO2 in global carbon cycling has been the subject of a heated debate. On one hand, erosion exposes the previously encapsulated soil organic carbon (SOC), which may accelerate the mineralization of eroded SOC. On the other hand, deposition limits the decomposition of SOC upon burial, while incorporation of biomass at eroding sites replaces the lost SOC. So far, effects of erosion on CO2 emissions have largely been assessed by comparing SOC stocks at eroding and depositional sites. The underlying assumption for this approach is a non-selective transport of eroded SOC across a landscape. However, several recent publications showed both an at least temporary on-site enrichment of SOC in sediment as well as a preferential deposition of sediment particles with SOC concentrations that differed from the soil SOC. As a consequence, balances between eroding and depositional sites may over- or underestimate mineralization of eroded SOC during transport. Two Luvisols, from the villages of Möhlin and Movelier in northwest Switzerland, were used in this study. They have different mineral grain size distribution, organic carbon concentration and aggregate stability. Based on the concept of Equivalent Quartz Size (EQS), the eroded sediments were fractionated by a settling tube apparatus into six different size classes, according to their settling velocities and likely transport distances. According to the model developed by Starr et al., 2000, the likely transport distances of six EQS classes were grouped into three likely fates: deposited across landscapes, possibly transferred into rivers, and likely transferred into rivers. Respiration rates of the fractionated sediments were measured by gas chromatograph for 50 days. Our results show that 1) due to aggregation, 60% of the Möhlin eroded fractions and 82% of the Movelier fractions would be re-deposited in the terrestrial system, which strongly contrasts with their grain

Factors predisposing nursing home resident to inappropriate transfer to emergency department. The FINE study protocol.

PubMed

Perrin, Amélie; Tavassoli, Neda; Mathieu, Céline; Hermabessière, Sophie; Houles, Mathieu; McCambridge, Cécile; Magre, Elodie; Fernandez, Sophie; Caquelard, Anne; Charpentier, Sandrine; Lauque, Dominique; Azema, Olivier; Bismuth, Serge; Chicoulaa, Bruno; Oustric, Stéphane; Costa, Nadège; Molinier, Laurent; Vellas, Bruno; Bérard, Emilie; Rolland, Yves

2017-09-01

Each year, around one out of two nursing home (NH) residents are hospitalized in France, and about half to the emergency department (ED). These transfers are frequently inappropriate. This paper describes the protocol of the FINE study. The first aim of this study is to identify the factors associated with inappropriate transfers to ED. FINE is a case-control observational study. Sixteen hospitals participate. Inclusion period lasts 7 days per season in each center for a total period of inclusion of one year. All the NH residents admitted in ED during these periods are included. Data are collected in 4 times: before transfer in the NH, at the ED, in hospital wards in case of patient's hospitalization and at the patient's return to NH. The appropriateness of ED transfers (i.e. case versus control NH residents) is determined by a multidisciplinary team of experts. Our primary objective is to determine the factors predisposing NH residents to inappropriate transfer to ED. Our secondary objectives are to assess the cost of the transfers to ED; study the evolution of NH residents' functional status and the psychotropic and inappropriate drugs prescription between before and after the transfer; calculate the prevalence of potentially avoidable transfers to ED; and identify the factors predisposing NH residents to potentially avoidable transfer to ED. A better understanding of the determinant factors of inappropriate transfers to ED of NH residents may lead to proposals of recommendations of better practice in NH and would allow implementing quality improvement programs in the health organization.

Trophic transfer of microplastics in aquatic ecosystems: Identifying critical research needs.

PubMed

Au, Sarah Y; Lee, Cindy M; Weinstein, John E; van den Hurk, Peter; Klaine, Stephen J

2017-05-01

To evaluate the process of trophic transfer of microplastics, it is important to consider various abiotic and biotic factors involved in their ingestion, egestion, bioaccumulation, and biomagnification. Toward this end, a review of the literature on microplastics has been conducted to identify factors influencing their uptake and absorption; their residence times in organisms and bioaccumulation; the physical effects of their aggregation in gastrointestinal tracts; and their potential to act as vectors for the transfer of other contaminants. Limited field evidence from higher trophic level organisms in a variety of habitats suggests that trophic transfer of microplastics may be a common phenomenon and occurs concurrently with direct ingestion. Critical research needs include standardizing methods of field characterization of microplastics, quantifying uptake and depuration rates in organisms at different trophic levels, quantifying the influence that microplastics have on the uptake and/or depuration of environmental contaminants among different trophic levels, and investigating the potential for biomagnification of microplastic-associated chemicals. More integrated approaches involving computational modeling are required to fully assess trophic transfer of microplastics. Integr Environ Assess Manag 2017;13:505-509. © 2017 SETAC. © 2017 SETAC.

Mechanical Dissociation of Platelet Aggregates in Blood Stream

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

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

PubMed

Pérez, I; Pasandín, A R; Gallego, J

2012-01-01

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

Particle Aggregation During Fe(III) Bioreduction in Nontronite

NASA Astrophysics Data System (ADS)

Jaisi, D. P.; Dong, H.; Hi, Z.; Kim, J.

2005-12-01

This study was performed to evaluate the rate and mechanism of particle aggregation during bacterial Fe (III) reduction in different size fractions of nontronite and to investigate the role of different factors contributing to particle aggregation. To achieve this goal, microbial Fe(III) reduction experiments were performed with lactate as an electron donor, Fe(III) in nontronite as an electron acceptor, and AQDS as an electron shuttle in bicarbonate buffer using Shewanella putrefaceins CN32. These experiments were performed with and without Na- pyrophosphate as a dispersant in four size fractions of nontronite (0.12-0.22, 0.41-0.69, 0.73-0.96 and 1.42-1.8 mm). The rate of nontronite aggregation during the Fe(III) bioreduction was measured by analyzing particle size distribution using photon correlation spectroscopy (PCS) and SEM images analysis. Similarly, the changes in particle morphology during particle aggregation were determined by analyses of SEM images. Changes in particle surface charge were measured with electrophoretic mobility analyzer. The protein and carbohydrate fraction of EPS produced by cells during Fe(III) bioreduction was measured using Bradford and phenol-sulfuric acid extraction method, respectively. In the presence of the dispersant, the extent of Fe(III) bioreduction was 11.5-12.2% within the first 56 hours of the experiment. There was no measurable particle aggregation in control experiments. The PCS measurements showed that the increase in the effective diameter (95% percentile) was by a factor of 3.1 and 1.9 for particle size of 0.12-0.22 mm and 1.42-1.80 mm, respectively. The SEM image analyses also gave the similar magnitude of increase in particle size. In the absence of the dispersant, the extent of Fe(III) bioreduction was 13.4-14.5% in 56 hours of the experiment. The rate of aggregation was higher than that in the presence of the dispersant. The increase in the effective diameter (95% percentile) was by a factor of 13.6 and 4.1 for

University Technology Transfer Factors as Predictors of Entrepreneurial Orientation

ERIC Educational Resources Information Center

Kirkman, Dorothy M.

2011-01-01

University technology transfer is a collaborative effort between academia and industry involving knowledge sharing and learning. Working closely with their university partners affords biotechnology firms the opportunity to successfully develop licensed inventions and gain access to novel scientific and technological discoveries. These factors may…

Familial Aggregation of Insomnia.

PubMed

Jarrin, Denise C; Morin, Charles M; Rochefort, Amélie; Ivers, Hans; Dauvilliers, Yves A; Savard, Josée; LeBlanc, Mélanie; Merette, Chantal

2017-02-01

There is little information about familial aggregation of insomnia; however, this type of information is important to (1) improve our understanding of insomnia risk factors and (2) to design more effective treatment and prevention programs. This study aimed to investigate evidence of familial aggregation of insomnia among first-degree relatives of probands with and without insomnia. Cases (n = 134) and controls (n = 145) enrolled in a larger epidemiological study were solicited to invite their first-degree relatives and spouses to complete a standardized sleep/insomnia survey. In total, 371 first-degree relatives (Mage = 51.9 years, SD = 18.0; 34.3% male) and 138 spouses (Mage = 55.5 years, SD = 12.2; 68.1% male) completed the survey assessing the nature, severity, and frequency of sleep disturbances. The dependent variable was insomnia in first-degree relatives and spouses. Familial aggregation was claimed if the risk of insomnia was significantly higher in the exposed (relatives of cases) compared to the unexposed cohort (relatives of controls). The risk of insomnia was also compared between spouses in the exposed (spouses of cases) and unexposed cohort (spouses of controls). The risk of insomnia in exposed and unexposed biological relatives was 18.6% and 10.4%, respectively, yielding a relative risk (RR) of 1.80 (p = .04) after controlling for age and sex. The risk of insomnia in exposed and unexposed spouses was 9.1% and 4.2%, respectively; however, corresponding RR of 2.13 (p = .28) did not differ significantly. Results demonstrate evidence of strong familial aggregation of insomnia. Additional research is warranted to further clarify and disentangle the relative contribution of genetic and environmental factors in insomnia. © Sleep Research Society 2016. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

Identification and characterization of an oocyte factor required for development of porcine nuclear transfer embryos

PubMed Central

Miyamoto, Kei; Nagai, Kouhei; Kitamura, Naoya; Nishikawa, Tomoaki; Ikegami, Haruka; Binh, Nguyen T.; Tsukamoto, Satoshi; Matsumoto, Mai; Tsukiyama, Tomoyuki; Minami, Naojiro; Yamada, Masayasu; Ariga, Hiroyoshi; Miyake, Masashi; Kawarasaki, Tatsuo; Matsumoto, Kazuya; Imai, Hiroshi

2011-01-01

Nuclear reprogramming of differentiated cells can be induced by oocyte factors. Despite numerous attempts, these factors and mechanisms responsible for successful reprogramming remain elusive. Here, we identify one such factor, necessary for the development of nuclear transfer embryos, using porcine oocyte extracts in which some reprogramming events are recapitulated. After incubating somatic nuclei in oocyte extracts from the metaphase II stage, the oocyte proteins that were specifically and abundantly incorporated into the nuclei were identified by mass spectrometry. Among 25 identified proteins, we especially focused on a multifunctional protein, DJ-1. DJ-1 is present at a high concentration in oocytes from the germinal vesicle stage until embryos at the four-cell stage. Inhibition of DJ-1 function compromises the development of nuclear transfer embryos but not that of fertilized embryos. Microarray analysis of nuclear transfer embryos in which DJ-1 function is inhibited shows perturbed expression of P53 pathway components. In addition, embryonic arrest of nuclear transfer embryos injected with anti–DJ-1 antibody is rescued by P53 inhibition. We conclude that DJ-1 is an oocyte factor that is required for development of nuclear transfer embryos. This study presents a means for identifying natural reprogramming factors in mammalian oocytes and a unique insight into the mechanisms underlying reprogramming by nuclear transfer. PMID:21482765

Evaluation of particle shape and texture of mineral aggregates and their blends

DOT National Transportation Integrated Search

1992-05-01

Two important factors for minimizing rutting of hot mix asphalt (HMA) mixtures are: a) the fractured face count of aggregate when gravel is used as coarse aggregate, and b) the use of manufactured sand. Both these factors relate to the shape and text...

DEVELOPMENT AND EVALUATION OF AN AGGREGATE SURFACE SAMPLING METHOD FOR USE IN ASSESSING DERMAL EXPOSURES OF YOUNG CHILDREN

EPA Science Inventory

In the macroactivity approach, dermal exposure is estimated using empirically-derived transfer coefficients to aggregate the mass transfer associated with a series of contacts with a contaminated medium. The macroactivity approach affords the possibility of developing screenin...

Transfer of Patients in a Telestroke Network: What Are the Relevant Factors for Making This Decision?

PubMed

Klingner, Carsten M; Brodoehl, Stefan; Funck, Laura; Klingner, Caroline C; Berrouschot, Jörg; Witte, Otto W; Günther, Albrecht

2018-02-01

Background/Introduction: Current telestroke network consultations are focused on decision-making in the hyperacute stage of stroke management. The two main questions in telestroke consultations are whether thrombolysis should be initiated and whether the patient should be transferred to a hub hospital. Although guidelines exist for initiating intravenous thrombolytic therapy, the question of whether patients should be transferred is far more elusive. In this study, we investigated the factors involved in the decision to transfer stroke patients to a hub hospital. We were particularly interested in identifying factors that promote or impede the transfer of patients. We enrolled 1,615 cases of telestroke consultation of the University Hospital Jena. The two main factors that independently influenced the probability of transferring a patient were the patient's age and the identification of a proximal vessel occlusion. Interestingly, factors such as the severity of symptoms and the time elapsed from symptom onset were not found to have an independent influence on the decision to transfer a patient. The transfer of most patients was justified by the possibility of performing interventional reperfusion therapy. We discuss the effectiveness of the current decision-making process and possible ways to improve decision-making for a more effective selection of patients who would benefit from transfer. The decision-making process to a transfer patient is not standardized and constitutes a trade-off between the intention to treat all possible patients while avoiding the transfer of patients without treatment options.

Quantitative analysis of in situ optical diagnostics for inferring particle/aggregate parameters in flames: Implications for soot surface growth and total emissivity

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

Koeylue, U.O.

1997-05-01

An in situ particulate diagnostic/analysis technique is outlined based on the Rayleigh-Debye-Gans polydisperse fractal aggregate (RDG/PFA) scattering interpretation of absolute angular light scattering and extinction measurements. Using proper particle refractive index, the proposed data analysis method can quantitatively yield all aggregate parameters (particle volume fraction, f{sub v}, fractal dimension, D{sub f}, primary particle diameter, d{sub p}, particle number density, n{sub p}, and aggregate size distribution, pdf(N)) without any prior knowledge about the particle-laden environment. The present optical diagnostic/interpretation technique was applied to two different soot-containing laminar and turbulent ethylene/air nonpremixed flames in order to assess its reliability. The aggregate interpretationmore » of optical measurements yielded D{sub f}, d{sub p}, and pdf(N) that are in excellent agreement with ex situ thermophoretic sampling/transmission electron microscope (TS/TEM) observations within experimental uncertainties. However, volume-equivalent single particle models (Rayleigh/Mie) overestimated d{sub p} by about a factor of 3, causing an order of magnitude underestimation in n{sub p}. Consequently, soot surface areas and growth rates were in error by a factor of 3, emphasizing that aggregation effects need to be taken into account when using optical diagnostics for a reliable understanding of soot formation/evolution mechanism in flames. The results also indicated that total soot emissivities were generally underestimated using Rayleigh analysis (up to 50%), mainly due to the uncertainties in soot refractive indices at infrared wavelengths. This suggests that aggregate considerations may not be essential for reasonable radiation heat transfer predictions from luminous flames because of fortuitous error cancellation, resulting in typically a 10 to 30% net effect.« less

Biological framework for soil aggregation: Implications for ecological functions.

NASA Astrophysics Data System (ADS)

Ghezzehei, Teamrat; Or, Dani

2016-04-01

Soil aggregation is heuristically understood as agglomeration of primary particles bound together by biotic and abiotic cementing agents. The organization of aggregates is believed to be hierarchical in nature; whereby primary particles bond together to form secondary particles and subsequently merge to form larger aggregates. Soil aggregates are not permanent structures, they continuously change in response to internal and external forces and other drivers, including moisture, capillary pressure, temperature, biological activity, and human disturbances. Soil aggregation processes and the resulting functionality span multiple spatial and temporal scales. The intertwined biological and physical nature of soil aggregation, and the time scales involved precluded a universally applicable and quantifiable framework for characterizing the nature and function of soil aggregation. We introduce a biophysical framework of soil aggregation that considers the various modes and factors of the genesis, maturation and degradation of soil aggregates including wetting/drying cycles, soil mechanical processes, biological activity and the nature of primary soil particles. The framework attempts to disentangle mechanical (compaction and soil fragmentation) from in-situ biophysical aggregation and provides a consistent description of aggregate size, hierarchical organization, and life time. It also enables quantitative description of biotic and abiotic functions of soil aggregates including diffusion and storage of mass and energy as well as role of aggregates as hot spots of nutrient accumulation, biodiversity, and biogeochemical cycles.

Aggregate nanostructures of organic molecular materials.

PubMed

Liu, Huibiao; Xu, Jialiang; Li, Yongjun; Li, Yuliang

2010-12-21

Conjugated organic molecules are interesting materials because of their structures and their electronic, electrical, magnetic, optical, biological, and chemical properties. However, researchers continue to face great challenges in the construction of well-defined organic compounds that aggregate into larger molecular materials such as nanowires, tubes, rods, particles, walls, films, and other structural arrays. Such nanoscale materials could serve as direct device components. In this Account, we describe our recent progress in the construction of nanostructures formed through the aggregation of organic conjugated molecules and in the investigation of the optical, electrical, and electronic properties that depend on the size or morphology of these nanostructures. We have designed and synthesized functional conjugated organic molecules with structural features that favor assembly into aggregate nanostructures via weak intermolecular interactions. These large-area ordered molecular aggregate nanostructures are based on a variety of simpler structures such as fullerenes, perylenes, anthracenes, porphyrins, polydiacetylenes, and their derivatives. We have developed new methods to construct these larger structures including organic vapor-solid phase reaction, natural growth, association via self-polymerization and self-organization, and a combination of self-assembly and electrochemical growth. These methods are both facile and reliable, allowing us to produce ordered and aligned aggregate nanostructures, such as large-area arrays of nanowires, nanorods, and nanotubes. In addition, we can synthesize nanoscale materials with controlled properties. Large-area ordered aggregate nanostructures exhibit interesting electrical, optical, and optoelectronic properties. We also describe the preparation of large-area aggregate nanostructures of charge transfer (CT) complexes using an organic solid-phase reaction technique. By this process, we can finely control the morphologies and

Chemical elements in pearl oysters (Paxyodon ponderosus), phytoplankton and estuarine sediments from eastern Amazon (Northern Brazil): Bioaccumulation factors and trophic transfer factors

NASA Astrophysics Data System (ADS)

Vilhena, Maria P. S. P.; Costa, Marcondes L.; Berrêdo, José F.; Paiva, Rosildo S.; Souza, Crisvaldo C. S.

2016-04-01

The current study was conducted near Barcarena County, which is a mid-sized urban center where aluminum ore processing industries (bauxite) and Vila do Conde cargo terminal are located. It aims to discuss the bioaccumulation factors as well as factors related to the trophic transfer of chemical elements in water, oyster, phytoplankton and bottom sediments from an estuary in the Brazilian Northern coast. The bioaccumulation factor (BAF), trophic transfer factor (TTF) and biota-sediment-water were used to correlate the contents of chemical elements found in organisms. The sediment, surface water, phytoplankton and pearl oysters chemical composition was analyzed by ICP-OES and ICP-MS. Pearl oysters showed K, Ca, Mg, P, Mn, Fe, Zn, Al, Ba and Pb accumulation, which concentration increase is associated with their diet (phytoplankton). Al concentrations are 14 times higher in pearl oysters (Paxyodon ponderosus), assuming that they are associated with wastewater emissions and with industrialization processes in the area. BAF and BSAF values are 1000 times higher than the metal concentrations in water and bioavailable fraction concentrations. The oyster-phytoplankton trophic transfer factor indicates that P, Ba, Ca, Na, Cd and Zn showed the largest transfers (from 5 to 19). These trophic transfers may be sufficient to cause significant ecotoxicological effects on the region biota.

Aggregation of recombinant human botulinum protein antigen serotype C in varying solution conditions: implications of conformational stability for aggregation kinetics.

PubMed

Bai, Shujun; Manning, Mark Cornell; Randolph, Theodore W; Carpenter, John F

2011-03-01

Solution conditions greatly affect the aggregation rate of a protein. Elucidating these influences provides insight into the critical factors governing aggregation. In this study, recombinant human botulinum protein antigen serotype C [rBoNTC (H(c))] was employed as a model protein. rBoNTC (H(c)) aggregated irreversibly during incubation at 42°C. The aggregation rate was studied as a function of solution conditions, including varying the pH from 3.5 to 8.0 and with or without 150 mM NaCl, 7.5% (w/v) trehalose, and 0.5 M urea. Some solution conditions retarded rBoNTC (H(c)) aggregation, whereas others accelerated aggregation, particularly acidic pH and addition of NaCl or urea. To better understand the mechanism by which these solution conditions influenced aggregation rates, the structure of rBoNTC (H(c)) was characterized using circular dichroism, fluorescence, and ultraviolet absorbance spectroscopies. Conformational stability was assessed from equilibrium urea-induced unfolding studies and by using differential scanning calorimetry (DSC). The activation energy of the aggregation reaction (E(a)) was estimated from an analysis of the heating-rate dependence of the thermal transition observed during DSC heating scans. Overall, for rBoNTC (H(c)), an inverse correlation was found between conformational stability and aggregation rate, as well as between the kinetic barrier to unfolding (i.e., E(a)) and aggregation rate. Copyright © 2010 Wiley-Liss, Inc.

Scale-model charge-transfer technique for measuring enhancement factors

NASA Technical Reports Server (NTRS)

Kositsky, J.; Nanevicz, J. E.

1991-01-01

Determination of aircraft electric field enhancement factors is crucial when using airborne field mill (ABFM) systems to accurately measure electric fields aloft. SRI used the scale model charge transfer technique to determine enhancement factors of several canonical shapes and a scale model Learjet 36A. The measured values for the canonical shapes agreed with known analytic solutions within about 6 percent. The laboratory determined enhancement factors for the aircraft were compared with those derived from in-flight data gathered by a Learjet 36A outfitted with eight field mills. The values agreed to within experimental error (approx. 15 percent).

Exciton–exciton annihilation as a probe of interchain interactions in PPV–oligomer aggregates

DOE PAGES

Peteanu, Linda A.; Chowdhury, Sanchari; Wildeman, Jurjen; ...

2017-01-20

One measure of exciton mobility in an aggregate is the efficiency of exciton–exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH–PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed frommore » the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. Furthermore, the wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.« less

Extracting Spectroscopic Factors of Argon Isotopes from Transfer Reactions

NASA Astrophysics Data System (ADS)

Manfredi, Juan; Tsang, M. B.; Lynch, W. G.; Brown, K. W.; Cerizza, G.; Barney, J.; Estee, J.; Loelius, C.; Sweany, S.; Anderson, C.; Setiawan, H.; Winkelbauer, J.; Smith, K.; Lee, J.; Xu, Z.; Rogers, A.; Pruitt, C.; Chajecki, Z.; Chen, G.; Langer, C.; Xiao, Z.; Li, Z.; Niu, C.

2017-09-01

A spectroscopic factor (SF) quantifies the single particle structure of a given state in a nucleus. There is a discrepancy in extracted SF's between studies that use transfer reactions and those that use knockout reactions. Resolving this discrepancy is important both for understanding reaction probes as well as constraining nuclear structure theory. Kinematically complete measurements of the transfer reactions 34Ar(p,d) and 46Ar(p,d) were performed at the National Superconducting Cyclotron Laboratory. The same beam energy (70 MeV/u) was used as in a previous knockout measurement to account for energy dependence in the relevant optical potentials. Preliminary results will be presented. In addition, findings from measurement of the two-neutron transfer reactions 34Ar(p,t) and 4 6 Ar(p,t) will be discussed. This work was supported by the NSF (PHY 1565546) and the DOE NNSA Stewardship Science Graduate Fellowship.

First-principles calculation of the optical properties of an amphiphilic cyanine dye aggregate.

PubMed

Haverkort, Frank; Stradomska, Anna; de Vries, Alex H; Knoester, Jasper

2014-02-13

Using a first-principles approach, we calculate electronic and optical properties of molecular aggregates of the dye amphi-pseudoisocyanine, whose structures we obtained from molecular dynamics (MD) simulations of the self-aggregation process. Using quantum chemistry methods, we translate the structural information into an effective time-dependent Frenkel exciton Hamiltonian for the dominant optical transitions in the aggregate. This Hamiltonian is used to calculate the absorption spectrum. Detailed analysis of the dynamic fluctuations in the molecular transition energies and intermolecular excitation transfer interactions in this Hamiltonian allows us to elucidate the origin of the relevant time scales; short time scales, on the order of up to a few hundreds of femtoseconds, result from internal motions of the dye molecules, while the longer (a few picosecond) time scales we ascribe to environmental motions. The absorption spectra of the aggregate structures obtained from MD feature a blue-shifted peak compared to that of the monomer; thus, our aggregates can be classified as H-aggregates, although considerable oscillator strength is carried by states along the entire exciton band. Comparison to the experimental absorption spectrum of amphi-PIC aggregates shows that the simulated line shape is too wide, pointing to too much disorder in the internal structure of the simulated aggregates.

Development and validation of a questionnaire to evaluate the factors influencing training transfer among nursing professionals.

PubMed

Bai, Yangjing; Li, Jiping; Bai, Yangjuan; Ma, Weiguang; Yang, Xiangyu; Ma, Fang

2018-02-13

Most organizations invest in people for training to improve human capital and maximize profitability. Yet it is reported in industry and nursing as well that training effectiveness is constrained because of inadequate transfer of training and the underlying reasons for the transfer problem remain unknown. And there is lack of tool to measure transfer problem. The purpose of this study was to develop and validate a questionnaire to evaluate the scores of factors influencing training transfer (FITT) among nursing professionals. The questionnaire was developed by item generation through interview with nurses and literature review. The FITT was validated in terms of content validity through expert reviews. Psychometric properties of the final instrument were assessed in a sample of 960 nurses with training experiences. The content validity of the instrument were as follows: the IR was 0.8095. 51 items on the 63-item scale had I-CVIs of 1.0 and the remaining 12 items had I-CVIs of 0.88. The S-CVI/UA was 0.976 and the S-CVI/Ave was 0.977. For the exploratory step, principal axis factoring (PAF) was selected for this study. Parallel analysis was used to decide the number of factors to extract and oblimin rotation method was used. Exploratory factor analysis identified a five-factor solution including 53 items, accounting for 68.23% of the total variance. The confirmatory factor analysis showed some support for this five-factor model. The findings demonstrate high internal consistency (Cronbach's alpha = .965). This study indicates that the FITT is a valid and reliable instrument for assessing the factors influencing training transfer among nursing professionals. The FITT can be used to assess individual perceptions of catalysts and barriers to the transfer of training among nursing professionals, which can help promote training transfer and training effectiveness in the workplace.

Factors predicting training transfer in health professionals participating in quality improvement educational interventions.

PubMed

Eid, Ahmed; Quinn, Doris

2017-01-31

Predictors of quality improvement (QI) training transfer are needed. This study aimed to identify these predictors among health professionals who participated in a QI training program held at a large hospital in the United States between 2005 and 2014. It also aimed to determine how these predictive factors facilitated or impeded QI training transfer. Following the Success Case Method, we used a screening survey to identify trainees with high and low levels of training transfer. We then conducted semistructured interviews with a sample of the survey respondents to document how training transfer was achieved and how lack of training transfer could be explained. The survey's response rate was 43%, with a Cronbach alpha of 0.89. We then conducted a thematic analysis of the interview transcripts of 16 physicians. The analysis revealed 3 categories of factors influencing the transfer of QI training: trainee characteristics, training course, and work environment. Relevant trainee characteristics included attitude toward change, motivation, mental processing skills, interpersonal skills, and the personality characteristics curiosity, humility, conscientiousness, resilience, wisdom, and positivity. The training project, team-based learning, and lectures were identified as relevant aspects of the training course. Work culture, work relationships, and resources were subthemes of the work environment category. We identified several QI training transfer predictors in our cohort of physicians. We hypothesize that some of these predictors may be more relevant to QI training transfer. Our results will help organizational leaders select trainees who are most likely to transfer QI training and to ensure that their work environments are conducive to QI training transfer.

Factors in the Transfer of Governance-Facilitation Skills within Farmers' Marketing Organizations in Uganda

ERIC Educational Resources Information Center

Miiro, Richard F.; Mazur, Robert E.; Matsiko, Frank B.

2012-01-01

Purpose: Training transfer has been examined for formal industrial and service organizations in developed countries but rarely for rural organizations in sub-Saharan Africa. This study sought to identify transfer system factors that best explain the transfer of governance-facilitation skills provided to leaders of farmers' marketing organizations…

Repeated measurements of transfer factor in rabbits: an animal model suitable for evaluation of short-term exposure.

PubMed

Dahlqvist, M; Lagerstrand, L; Nilsen, A

1994-01-01

Acute temporary changes in lung function may be of use as a biological exposure indicator. However, studies of humans occupationally exposed to complex airborne irritants are often expensive and time demanding. Therefore, an animal model could be a valuable complement. A rabbit model has been evaluated where transfer factor was measured twice during the same day, and with the rabbit awake and available for exposure, in between. Anaesthesia and intubation in 22 rabbits (2.6 [0.2] kg [Mean (SD)]) were immediately followed by two measurements of transfer factor and alveolar volume. Transfer factor was estimated by the single breath CO-technique used in humans. The samples were analysed for CO and He on a gas chromatograph. After one pair of measurements the rabbit was allowed to wake up and after 5 h the duplicate measurements were repeated. The mean values of transfer factor, alveolar volume and transfer constant were 0.50 (0.09) mmol min-1 kPa-1, 127 (8) ml and 3.9 (0.6) mmol min-1 kPa-1 l-1, respectively. The intraindividual coefficients of variation were 7.3%, 5.3% and 6.7%, respectively. Five hours later when the duplicate measurements were repeated, transfer factor, alveolar volume and transfer constant were unchanged still. The results suggest that relatively small changes in transfer factor may be detected without losing power, and thus that this model could be used as a biological exposure indicator.

Training transfer: a systematic review of the impact of inner setting factors.

PubMed

Jackson, Carrie B; Brabson, Laurel A; Quetsch, Lauren B; Herschell, Amy D

2018-06-19

Consistent with Baldwin and Ford's model (Pers Psychol 41(1):63-105, 1988), training transfer is defined as the generalization of learning from a training to everyday practice in the workplace. The purpose of this review was to examine the influence of work-environment factors, one component of the model hypothesized to influence training transfer within behavioral health. An electronic literature search guided by the Consolidated Framework for Implementation Research's inner setting domain was conducted was conducted on Medline OVID, Medline EMBASE, and PsycINFO databases. Of 9184 unique articles, 169 full-text versions of articles were screened for eligibility, yielding 26 articles meeting inclusion criteria. Results from the 26 studies revealed that overall, having more positive networks and communication, culture, implementation climate, and readiness for implementation can facilitate training transfer. Although few studies have examined the impact of inner setting factors on training transfer, these results suggest organizational context is important to consider with training efforts. These findings have important implications for individuals in the broader health professions educational field.

Melanosome transfer to and translocation in the keratinocyte.

PubMed

Boissy, Raymond E

2003-01-01

Complexion coloration in humans is primarily regulated by the amount and type of melanin synthesized by the epidermal melanocyte. However, additional and equally contributing factors consist of (1) efficient transfer of melanin from the melanocytes to the neighboring keratinocytes and (2) distribution and degradation of the transferred melanosomes by the recipient keratinocytes. Once synthesized in the cell body of the epidermal melanocyte, pigmented melanosomes are translocated down the dendrites and captured at the dendritic tips via various cytoskeletal elements. Molecules recently identified that participate in this process consist of Rab27a, myosin-Va and melanophilin. Eventually, these peripherally localized melanosomes are transferred to keratinocytes by a presently undefined mechanism. The protease-activated receptor-2 (PAR-2) and unidentified surface lectins and glycoproteins facilitate this transfer process. Once incorporated into the keratinocytes, melanosomes are distributed individually or as clusters, aggregated towards the apical pole of the nucleus, and degraded as the keratinocytes undergo terminal differentiation and desquamation. Ultraviolet irradiation (UVR) can modulate the process of melanosome transfer from the melanocytes to the keratinocytes. UVR can upregulate expression of PAR-2 and lectin-binding receptors and increase phagocytic activity of cultured keratinocytes. Therefore, many cellular and molecular events that occur after melanogenesis contribute to skin color.

How important are dual economy effects for aggregate productivity?

PubMed Central

Vollrath, Dietrich

2013-01-01

This paper brings together development accounting techniques and the dual economy model to address the role that factor markets have in creating variation in aggregate total factor productivity (TFP). Development accounting research has shown that much of the variation in income across countries can be attributed to differences in TFP. The dual economy model suggests that aggregate productivity is depressed by having too many factors allocated to low productivity work in agriculture. Data show large differences in marginal products of similar factors within many developing countries, offering prima facie evidence of this misallocation. Using a simple two-sector decomposition of the economy, this article estimates the role of these misallocations in accounting for the cross-country income distribution. A key contribution is the ability to bring sector-specific data on human and physical capital stocks to the analysis. Variation across countries in the degree of misallocation is shown to account for 30–40% of the variation in income per capita, and up to 80% of the variation in aggregate TFP. PMID:23946553

Smart-aggregate-based damage detection of fiber-reinforced-polymer-strengthened columns under reversed cyclic loading

NASA Astrophysics Data System (ADS)

Howser, Rachel; Moslehy, Yashar; Gu, Haichang; Dhonde, Hemant; Mo, Y. L.; Ayoub, Ashraf; Song, Gangbing

2011-07-01

Structural health monitoring is an important aspect of the maintenance of large civil infrastructures, especially for bridge columns in areas of high seismic activity. In this project, recently developed innovative piezoceramic-based sensors were utilized to perform the health monitoring of a shear-critical reinforced concrete (RC) bridge column subjected to reversed cyclic loading. After the column failed, it was wrapped with fiber reinforced polymer (FRP) sheets, commonly used to retrofit seismically damaged structures. The FRP-strengthened column was retested under the same reversed cyclic loading pattern. Innovative piezoceramic-based sensors, called 'smart aggregates', were utilized as transducers for health monitoring purposes. On the basis of the smart aggregates developed, an active-sensing approach and an impact-hammer-based approach were used to evaluate the health status of the RC column during the loading procedure. Wave transmission energy is attenuated by the existence of cracks during the loading procedure, and this attenuation phenomenon alters the curve of the transfer function between the actuator and sensor. To detect the damage occurrence and evaluate the damage severity, transfer function curves were compared with those obtained during the period of healthy status. A transfer-function-based damage index matrix was developed to demonstrate the damage severity at different locations. Experimental results verified the effectiveness of the smart aggregates in health monitoring of the FRP-strengthened column as well as the unstrengthened column. The experimental results show that the proposed smart-aggregate-based approach can successfully detect damage occurrence and evaluate its severity.

Lawrence Transfer Factor: Transference of Specific Immune Memory by Dialyzable Leukocyte Extract from a CD8+ T Cell Line.

PubMed

Wang, Jason F; Park, Andrew J; Rendini, Tina; Levis, William R

2017-12-01

Lawrence transfer factor (TF) is defined as dialyzable leukocyte extract (DLE) that can transfer antigen-specific cell-mediated immunity from a person testing positive for the antigen in a delayed type hypersensitivity skin test manner to a person negative for the same antigen. A recent article by Myles et al1 has identified a DLE isolated from an established CD8+ T cell line capable of transferring antigen-specific immunity. The DLE contains a portion of the beta chain of the T cell receptor and additional nucleotide and protein factors that are being subjected to further modern biochemical analysis. After months of study that included interviews of TF physician-scientists, we conclude that an antigen-specific TF exists for most, if not all, antigens. By working from a CD8+ T cell line with modern biochemical technology, it should be possible to identify and patent products capable of treating infectious diseases, antigen-responsive cancers, and autoimmune disorders.

Chaperones in Polyglutamine Aggregation: Beyond the Q-Stretch

PubMed Central

Kuiper, E. F. E.; de Mattos, Eduardo P.; Jardim, Laura B.; Kampinga, Harm H.; Bergink, Steven

2017-01-01

Expanded polyglutamine (polyQ) stretches in at least nine unrelated proteins lead to inherited neuronal dysfunction and degeneration. The expansion size in all diseases correlates with age at onset (AO) of disease and with polyQ protein aggregation, indicating that the expanded polyQ stretch is the main driving force for the disease onset. Interestingly, there is marked interpatient variability in expansion thresholds for a given disease. Between different polyQ diseases the repeat length vs. AO also indicates the existence of modulatory effects on aggregation of the upstream and downstream amino acid sequences flanking the Q expansion. This can be either due to intrinsic modulation of aggregation by the flanking regions, or due to differential interaction with other proteins, such as the components of the cellular protein quality control network. Indeed, several lines of evidence suggest that molecular chaperones have impact on the handling of different polyQ proteins. Here, we review factors differentially influencing polyQ aggregation: the Q-stretch itself, modulatory flanking sequences, interaction partners, cleavage of polyQ-containing proteins, and post-translational modifications, with a special focus on the role of molecular chaperones. By discussing typical examples of how these factors influence aggregation, we provide more insight on the variability of AO between different diseases as well as within the same polyQ disorder, on the molecular level. PMID:28386214

Calcium oxalate monohydrate aggregation induced by aggregation of desialylated Tamm-Horsfall protein

PubMed Central

Viswanathan, Pragasam; Rimer, Jeffrey D.; Kolbach, Ann M.; Kleinman, Jack G.

2011-01-01

Tamm-Horsfall protein (THP) is thought to protect against calcium oxalate monohydrate (COM) stone formation by inhibiting COM aggregation. Several studies reported that stone formers produce THP with reduced levels of glycosylation, particularly sialic acid levels, which leads to reduced negative charge. In this study, normal THP was treated with neuraminidase to remove sialic acid residues, confirmed by an isoelectric point shift to higher pH. COM aggregation assays revealed that desialylated THP (ds-THP) promoted COM aggregation, while normal THP inhibited aggregation. The appearance of protein aggregates in solutions at ds-THP concentrations ≥1 µg/mL in 150 mM NaCl correlated with COM aggregation promotion, implying that ds-THP aggregation induced COM aggregation. The aggregation-promoting effect of the ds-THP was independent of pH above its isoelectric point, but was substantially reduced at low ionic strength, where protein aggregation was much reduced. COM aggregation promotion was maximized at a ds-THP to COM mass ratio of ~0.025, which can be explained by a model wherein partial COM surface coverage by ds-THP aggregates promotes crystal aggregation by bridging opposing COM surfaces, whereas higher surface coverage leads to repulsion between adsorbed ds-THP aggregates. Thus, desialylation of THP apparently abrogates a normal defensive action of THP by inducing protein aggregation, and subsequently COM aggregation, a condition that favors kidney stone formation. PMID:21229239

Rydberg aggregates

NASA Astrophysics Data System (ADS)

Wüster, S.; Rost, J.-M.

2018-02-01

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

Does bathymetry drive coastal whale shark (Rhincodon typus) aggregations?

PubMed Central

Stewart, Bryce D.; McClean, Colin J.; Hancock, James; Rees, Richard

2018-01-01

Background The whale shark (Rhincodon typus) is known to aggregate in a number of coastal locations globally, however what causes these aggregations to form where they do is largely unknown. This study examines whether bathymetry is an important driver of coastal aggregation locations for R. typus through bathymetry’s effect on primary productivity and prey availability. This is a global study taking into account all coastal areas within R. typus’ range. Methods R. typus aggregation locations were identified through an extensive literature review. Global bathymetric data were compared at R. typus aggregation locations and a large random selection of non-aggregation areas. Generalised linear models were used to assess which bathymetric characteristic had the biggest influence on aggregation presence. Results Aggregation sites were significantly shallower than non-aggregation sites and in closer proximity to deep water (the mesopelagic zone) by two orders of magnitude. Slope at aggregation sites was significantly steeper than non-aggregation sites. These three bathymetric variables were shown to have the biggest association with aggregation sites, with up to 88% of deviation explained by the GLMs. Discussion The three key bathymetric characteristics similar at the aggregation sites are known to induce upwelling events, increase primary productivity and consequently attract numerous other filter feeding species. The location of aggregation sites in these key areas can be attributed to this increased prey availability, thought to be the main reason R. typus aggregations occur, extensively outlined in the literature. The proximity of aggregations to shallow areas such as reefs could also be an important factor why whale sharks thermoregulate after deep dives to feed. These findings increase our understanding of whale shark behaviour and may help guide the identification and conservation of further aggregation sites.

AAV5-Factor VIII Gene Transfer in Severe Hemophilia A.

PubMed

Rangarajan, Savita; Walsh, Liron; Lester, Will; Perry, David; Madan, Bella; Laffan, Michael; Yu, Hua; Vettermann, Christian; Pierce, Glenn F; Wong, Wing Y; Pasi, K John

2017-12-28

Patients with hemophilia A rely on exogenous factor VIII to prevent bleeding in joints, soft tissue, and the central nervous system. Although successful gene transfer has been reported in patients with hemophilia B, the large size of the factor VIII coding region has precluded improved outcomes with gene therapy in patients with hemophilia A. We infused a single intravenous dose of a codon-optimized adeno-associated virus serotype 5 (AAV5) vector encoding a B-domain-deleted human factor VIII (AAV5-hFVIII-SQ) in nine men with severe hemophilia A. Participants were enrolled sequentially into one of three dose cohorts (low dose [one participant], intermediate dose [one participant], and high dose [seven participants]) and were followed through 52 weeks. Factor VIII activity levels remained at 3 IU or less per deciliter in the recipients of the low or intermediate dose. In the high-dose cohort, the factor VIII activity level was more than 5 IU per deciliter between weeks 2 and 9 after gene transfer in all seven participants, and the level in six participants increased to a normal value (>50 IU per deciliter) that was maintained at 1 year after receipt of the dose. In the high-dose cohort, the median annualized bleeding rate among participants who had previously received prophylactic therapy decreased from 16 events before the study to 1 event after gene transfer, and factor VIII use for participant-reported bleeding ceased in all the participants in this cohort by week 22. The primary adverse event was an elevation in the serum alanine aminotransferase level to 1.5 times the upper limit of the normal range or less. Progression of preexisting chronic arthropathy in one participant was the only serious adverse event. No neutralizing antibodies to factor VIII were detected. The infusion of AAV5-hFVIII-SQ was associated with the sustained normalization of factor VIII activity level over a period of 1 year in six of seven participants who received a high dose, with

Synthesis and studies of axial chiral bisbenzocoumarins: Aggregation-induced emission enhancement properties and aggregation-annihilation circular dichroism effects

NASA Astrophysics Data System (ADS)

Chen, Shaojin; Liu, Wei; Ge, Zhaohai; Zhang, Wenxuan; Wang, Kunpeng; Hu, Zhiqiang

2018-03-01

Axial chiral bisbenzocoumarins were synthesized for the first time by converting naphthanol units in 1,1‧-binaphthol (BINOL) molecule to the benzocoumarin rings. The substitute groups on 3,3‧-positions of bisbenzocoumarins showed significant influence on their aggregation-induced emission enhancement (AEE) properties. It was also found that BBzC1 with ester groups on 3,3‧-positions exhibit an abnormal aggregation-annihilation circular dichroism (AACD) phenomenon, which could be caused by the decrease of the dihedral angle between adjacent benzocoumarin rings in the aggregation state. The single crystal structure of BBzC1 showed that the large dihedral angle in molecule prohibited the strong π-π stacking interactions, which could be main factors for its AEE properties.

Transportation and utilization of aggregates for road construction

NASA Astrophysics Data System (ADS)

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

2017-04-01

, and aggregate sizes for unbound materials varies from 19 mm to 600 mm. These results imply great differences in the amount of aggregate transport to road construction sites. Another important factor is the distances between the construction sites and the aggregate sources. For many projects, especially in countries in need of importing aggregates, aggregate transport will have considerable impact on sustainability assessment of the construction projects. If pavement design can be altered with the goal of achieving better utilization of local aggregates through adaption to the quality of local aggregates, aggregate transportation can be reduced. Reduced transport will alter the economical balance of a project, allowing reallocation of costs from transport to e.g. improved aggregate production. The overall result can be more profitable construction projects and a more sustainable development of road structures.

Interrelationships of metal transfer factor under wastewater reuse and soil pollution.

PubMed

Papaioannou, D; Kalavrouziotis, I K; Koukoulakis, P H; Papadopoulos, F; Psoma, P

2018-06-15

The transfer of heavy metals under soil pollution wastewater reuse was studied in a Greenhouse experiment using a randomized block design, including 6 treatments of heavy metals mixtures composed of Zn, Mn, Cd, Co, Cu, Cr, Ni, and Pb, where each metal was taking part in the mixture with 0, 10, 20, 30, 40, 50 mg/kg respectively, in four replications. The Beta vulgaris L (beet) was used as a test plant. It was found that the metal transfer factors were statistically significantly related to the: (i) DTPA extractable soil metals, (ii) the soil pollution level as assessed by the pollution indices, (iii) the soil pH, (iv) the beet dry matter yield and (v) the interactions between the heavy metals in the soil. It was concluded that the Transfer Factor is subjected to multifactor effects and its real nature is complex, and there is a strong need for further study for the understanding of its role in metal-plant relationships. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of the LHCII pigment-protein complex aggregation on photovoltaic properties of sensitized TiO2 solar cells.

PubMed

Yang, Yiqun; Jankowiak, Ryszard; Lin, Chen; Pawlak, Krzysztof; Reus, Michael; Holzwarth, Alfred R; Li, Jun

2014-10-14

A modified dye-sensitized solar cell consisting of a thin TiO2 barrier layer sensitized with natural trimeric light-harvesting complex II (LHCII) from spinach was used as a biomimetic model to study the effects of LHCII aggregation on the photovoltaic properties. The aggregation of individual trimers induced molecular reorganization, which dramatically increased the photocurrent. The morphology of small- and large-size LHCII aggregates deposited on a surface was confirmed by atomic force microscopy. Enhanced LHCII immobilization was accomplished via electrostatic interaction with amine-functionalized photoanodes. The photocurrent responses of the assembled solar cells under illumination at three characteristic wavelength bands in the UV-Vis absorption spectra of LHCII solutions confirmed that a significant photocurrent was generated by LHCII photosensitizers. The enhanced photocurrent by large aggregated LHCII is shown to correlate with the quenching in the far-red fluorescence deriving from chlorophyll-chlorophyll charge transfer states that are effectively coupled with the TiO2 surface and thus inject electrons into the TiO2 conduction band. The large aggregated LHCII with more chlorophyll-chlorophyll charge transfer states is a much better sensitizer since it injects electrons more efficiently into the conduction band of TiO2 than the small aggregated LHCII mostly consisting of unquenched chlorophyll excited state. The assembled solar cells demonstrated remarkable stability in both aqueous buffer and acetonitrile electrolytes over 30 days.

HESI EXPOSURE FACTORS DATABASE FOR AGGREGATE AND CUMULATIVE RISK ASSESSMENT

EPA Science Inventory

In recent years, the risk analysis community has broadened its use of complex aggregate and cumulative residential exposure models (e.g., to meet the requirements of the 1996 Food Quality Protection Act). The value of these models is their ability to incorporate a range of inp...

Time-fixed rendezvous by impulse factoring with an intermediate timing constraint. [for transfer orbits

NASA Technical Reports Server (NTRS)

Green, R. N.; Kibler, J. F.; Young, G. R.

1974-01-01

A method is presented for factoring a two-impulse orbital transfer into a three- or four-impulse transfer which solves the rendezvous problem and satisfies an intermediate timing constraint. Both the time of rendezvous and the intermediate time of a alinement are formulated as any element of a finite sequence of times. These times are integer multiples of a constant plus an additive constant. The rendezvous condition is an equality constraint, whereas the intermediate alinement is an inequality constraint. The two timing constraints are satisfied by factoring the impulses into collinear parts that vectorially sum to the original impulse and by varying the resultant period differences and the number of revolutions in each orbit. Five different types of solutions arise by considering factoring either or both of the two impulses into two or three parts with a limit for four total impulses. The impulse-factoring technique may be applied to any two-impulse transfer which has distinct orbital periods.

Influence of plankton community structure on the sinking velocity of marine aggregates

NASA Astrophysics Data System (ADS)

Bach, L. T.; Boxhammer, T.; Larsen, A.; Hildebrandt, N.; Schulz, K. G.; Riebesell, U.

2016-08-01

About 50 Gt of carbon is fixed photosynthetically by surface ocean phytoplankton communities every year. Part of this organic matter is reprocessed within the plankton community to form aggregates which eventually sink and export carbon into the deep ocean. The fraction of organic matter leaving the surface ocean is partly dependent on aggregate sinking velocity which accelerates with increasing aggregate size and density, where the latter is controlled by ballast load and aggregate porosity. In May 2011, we moored nine 25 m deep mesocosms in a Norwegian fjord to assess on a daily basis how plankton community structure affects material properties and sinking velocities of aggregates (Ø 80-400 µm) collected in the mesocosms' sediment traps. We noted that sinking velocity was not necessarily accelerated by opal ballast during diatom blooms, which could be due to relatively high porosity of these rather fresh aggregates. Furthermore, estimated aggregate porosity (Pestimated) decreased as the picoautotroph (0.2-2 µm) fraction of the phytoplankton biomass increased. Thus, picoautotroph-dominated communities may be indicative for food webs promoting a high degree of aggregate repackaging with potential for accelerated sinking. Blooms of the coccolithophore Emiliania huxleyi revealed that cell concentrations of 1500 cells/mL accelerate sinking by about 35-40%, which we estimate (by one-dimensional modeling) to elevate organic matter transfer efficiency through the mesopelagic from 14 to 24%. Our results indicate that sinking velocities are influenced by the complex interplay between the availability of ballast minerals and aggregate packaging; both of which are controlled by plankton community structure.

Nature of the narrow optical band in H*-aggregates: Dozy-chaos–exciton coupling

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

Egorov, Vladimir V., E-mail: egorov@photonics.ru

2014-07-15

Dozy chaos emerges as a combined effect of the collective chaotic motion of electrons and nuclei, and their chaotic electromagnetic interactions in the transient state of molecules experiencing quantum transitions. Following earlier discussions of the well-known Brönsted relations for proton-transfer reactions; the temperature-dependent electron transfer in Langmuir–Blodgett films; the shape of the optical bands of polymethine dye monomers, their dimers, and J-aggregates, this paper reports one more application of the dozy-chaos theory of molecular quantum transitions. The qualitative and quantitative explanations for shape of a narrow and blue-shifted optical absorption band in H{sup *}-aggregates is given on the basis ofmore » the dozy-chaos theory by taking into account the dozy-chaos–exciton coupling effect. It is emphasized that in the H{sup *}-aggregate chromophore (dimer of cyclic bis-thiacarbocyanines) there is a competition between two Frenkel exciton transitions through the chaotic reorganization motion of nuclear environment. As a result, the highly organized quantum transition to the upper exciton state becomes an exciton-induced source of dozy chaos for the low organized transition to the lower exciton state. This manifests itself in appearing the narrow peak and broad wing in the optical spectrum pattern of H{sup *}-aggregates. A similar enhancement in the H{sup *}-effect caused by the strengthening of the exciton coupling in H{sup *}-dimers, which could be achieved by synthesizing tertiary and quarternary thiacarbocyanine monomers, is predicted.« less

45 CFR 2530.50 - Is there a limit on the amount of transferred awards a designated individual may receive?

Code of Federal Regulations, 2010 CFR

2010-10-01

... education awards. If the sum of the value of the requested transfer plus the aggregate value of education... received the aggregate value of two full-time education awards, the individual may not receive a... to Public Welfare (Continued) CORPORATION FOR NATIONAL AND COMMUNITY SERVICE TRANSFER OF EDUCATION...

Trust-aware recommendation for improving aggregate diversity

NASA Astrophysics Data System (ADS)

Liu, Haifeng; Bai, Xiaomei; Yang, Zhuo; Tolba, Amr; Xia, Feng

2015-10-01

Recommender systems are becoming increasingly important and prevalent because of the ability of solving information overload. In recent years, researchers are paying increasing attention to aggregate diversity as a key metric beyond accuracy, because improving aggregate recommendation diversity may increase long tails and sales diversity. Trust is often used to improve recommendation accuracy. However, how to utilize trust to improve aggregate recommendation diversity is unexplored. In this paper, we focus on solving this problem and propose a novel trust-aware recommendation method by incorporating time factor into similarity computation. The rationale underlying the proposed method is that, trustees with later creation time of trust relation can bring more diverse items to recommend to their trustors than other trustees with earlier creation time of trust relation. Through relevant experiments on publicly available dataset, we demonstrate that the proposed method outperforms the baseline method in terms of aggregate diversity while maintaining almost the same recall.

Decisions to Transfer Nursing Home Residents to Emergency Departments: A Scoping Review of Contributing Factors and Staff Perspectives.

PubMed

Trahan, Lisa M; Spiers, Jude A; Cummings, Greta G

2016-11-01

Nursing home (NH) residents are a frail and vulnerable population often faced with iatrogenic effects of hospital stays when transferred to emergency departments for acute changes in health status. Avoidable or unnecessary transfers of care need to be identified and defined to prevent unintended harm. The aim of this scoping review was to identify characteristics of avoidable or unnecessary transitions of NH residents to emergency departments, and examine factors influencing decision-making by NH staff, residents, and their family members to transfer nursing home residents to emergency departments. The search strategy began with 5 electronic databases, and a hand search of gray literature. Published qualitative and quantitative studies were included that examined the definition of avoidable or unnecessary transfers, and/or reported factors associated with decision-making to transfer NH residents to emergency departments. Methods included quality assessments, data extraction, and synthesis using content analysis. A total of 783 titles and abstracts were retrieved and screened resulting in 19 included studies. Results describing "avoidable" or "unnecessary" transfers were grouped into 3 dimensions of factors: management of early-acute or low-acuity symptoms and chronic disease management in NHs, ambulatory care-sensitive indicators, and use of post hoc assessments. Five categories of factors contributing to decision-making to transfer were identified: nursing factors, physician factors, facility/resource factors, NH resident/family factors, and health system factors. A consensus on the definition of "avoidable" or "unnecessary" transfers was not found. Findings suggest that transfers of NH residents to emergency departments may be avoided with increased care capacity within NHs. The decision-making process involved in the transfer is influenced by many factors, with intentions of both improving clinical outcomes and maintaining quality of life for the NH resident

Automatic analysis of microscopic images of red blood cell aggregates

NASA Astrophysics Data System (ADS)

Menichini, Pablo A.; Larese, Mónica G.; Riquelme, Bibiana D.

2015-06-01

Red blood cell aggregation is one of the most important factors in blood viscosity at stasis or at very low rates of flow. The basic structure of aggregates is a linear array of cell commonly termed as rouleaux. Enhanced or abnormal aggregation is seen in clinical conditions, such as diabetes and hypertension, producing alterations in the microcirculation, some of which can be analyzed through the characterization of aggregated cells. Frequently, image processing and analysis for the characterization of RBC aggregation were done manually or semi-automatically using interactive tools. We propose a system that processes images of RBC aggregation and automatically obtains the characterization and quantification of the different types of RBC aggregates. Present technique could be interesting to perform the adaptation as a routine used in hemorheological and Clinical Biochemistry Laboratories because this automatic method is rapid, efficient and economical, and at the same time independent of the user performing the analysis (repeatability of the analysis).

Influence of the valine zipper region on the structure and aggregation of the basic leucine zipper (bZIP) domain of activating transcription factor 5 (ATF5).

PubMed

Ciaccio, Natalie A; Reynolds, T Steele; Middaugh, C Russell; Laurence, Jennifer S

2012-11-05

Protein aggregation is a major problem for biopharmaceuticals. While the control of aggregation is critically important for the future of protein pharmaceuticals, mechanisms of aggregate assembly, particularly the role that structure plays, are still poorly understood. Increasing evidence indicates that partially folded intermediates critically influence the aggregation pathway. We have previously reported the use of the basic leucine zipper (bZIP) domain of activating transcription factor 5 (ATF5) as a partially folded model system to investigate protein aggregation. This domain contains three regions with differing structural propensity: a N-terminal polybasic region, a central helical leucine zipper region, and a C-terminal extended valine zipper region. Additionally, a centrally positioned cysteine residue readily forms an intermolecular disulfide bond that reduces aggregation. Computational analysis of ATF5 predicts that the valine zipper region facilitates self-association. Here we test this hypothesis using a truncated mutant lacking the C-terminal valine zipper region. We compare the structure and aggregation of this mutant to the wild-type (WT) form under both reducing and nonreducing conditions. Our data indicate that removal of this region results in a loss of α-helical structure in the leucine zipper and a change in the mechanism of self-association. The mutant form displays increased association at low temperature but improved resistance to thermally induced aggregation.

Increased Zinc Availability Enhances Initial Aggregation and Biofilm Formation of Streptococcus pneumoniae

PubMed Central

Brown, Lindsey R.; Caulkins, Rachel C.; Schartel, Tyler E.; Rosch, Jason W.; Honsa, Erin S.; Schultz-Cherry, Stacey; Meliopoulos, Victoria A.; Cherry, Sean; Thornton, Justin A.

2017-01-01

Bacteria growing within biofilms are protected from antibiotics and the immune system. Within these structures, horizontal transfer of genes encoding virulence factors, and promoting antibiotic resistance occurs, making biofilms an extremely important aspect of pneumococcal colonization and persistence. Identifying environmental cues that contribute to the formation of biofilms is critical to understanding pneumococcal colonization and infection. Iron has been shown to be essential for the formation of pneumococcal biofilms; however, the role of other physiologically important metals such as copper, zinc, and manganese has been largely neglected. In this study, we investigated the effect of metals on pneumococcal aggregation and early biofilm formation. Our results show that biofilms increase as zinc concentrations increase. The effect was found to be zinc-specific, as altering copper and manganese concentrations did not affect biofilm formation. Scanning electron microscopy analysis revealed structural differences between biofilms grown in varying concentrations of zinc. Analysis of biofilm formation in a mutant strain lacking the peroxide-generating enzyme pyruvate oxidase, SpxB, revealed that zinc does not protect against pneumococcal H2O2. Further, analysis of a mutant strain lacking the major autolysin, LytA, indicated the role of zinc as a negative regulator of LytA-dependent autolysis, which could affect biofilm formation. Additionally, analysis of cell-cell aggregation via plating and microscopy revealed that high concentrations of zinc contribute to intercellular interaction of pneumococci. The findings from this study demonstrate that metal availability contributes to the ability of pneumococci to form aggregates and subsequently, biofilms. PMID:28638805

Increased Zinc Availability Enhances Initial Aggregation and Biofilm Formation of Streptococcus pneumoniae.

PubMed

Brown, Lindsey R; Caulkins, Rachel C; Schartel, Tyler E; Rosch, Jason W; Honsa, Erin S; Schultz-Cherry, Stacey; Meliopoulos, Victoria A; Cherry, Sean; Thornton, Justin A

2017-01-01

Bacteria growing within biofilms are protected from antibiotics and the immune system. Within these structures, horizontal transfer of genes encoding virulence factors, and promoting antibiotic resistance occurs, making biofilms an extremely important aspect of pneumococcal colonization and persistence. Identifying environmental cues that contribute to the formation of biofilms is critical to understanding pneumococcal colonization and infection. Iron has been shown to be essential for the formation of pneumococcal biofilms; however, the role of other physiologically important metals such as copper, zinc, and manganese has been largely neglected. In this study, we investigated the effect of metals on pneumococcal aggregation and early biofilm formation. Our results show that biofilms increase as zinc concentrations increase. The effect was found to be zinc-specific, as altering copper and manganese concentrations did not affect biofilm formation. Scanning electron microscopy analysis revealed structural differences between biofilms grown in varying concentrations of zinc. Analysis of biofilm formation in a mutant strain lacking the peroxide-generating enzyme pyruvate oxidase, SpxB, revealed that zinc does not protect against pneumococcal H 2 O 2 . Further, analysis of a mutant strain lacking the major autolysin, LytA, indicated the role of zinc as a negative regulator of LytA-dependent autolysis, which could affect biofilm formation. Additionally, analysis of cell-cell aggregation via plating and microscopy revealed that high concentrations of zinc contribute to intercellular interaction of pneumococci. The findings from this study demonstrate that metal availability contributes to the ability of pneumococci to form aggregates and subsequently, biofilms.

Effects of aggregation on the excitation dynamics of LH2 from Thermochromatium tepidum in aqueous phase and in chromatophores.

PubMed

Yang, Fan; Yu, Long-Jiang; Wang, Peng; Ai, Xi-Cheng; Wang, Zheng-Yu; Zhang, Jian-Ping

2011-06-23

We carried out femtosecond magic-angle and polarized pump-probe spectroscopies for the light-harvesting complex 2 (LH2) from Thermochromatium (Tch.) tepidum in aqueous phase and in chromatophores. To examine the effects of LH2 aggregation on the dynamics of excitation energy transfer, dominant monodispersed and aggregated LH2s were prepared by controlling the surfactant concentrations. The aqueous preparations solubilized with different concentrations of n-dodecyl-β-D-maltoside (DDM) show similar visible-to-near-infrared absorption spectra, but distinctively different aggregation states, as revealed by using dynamic light scattering. The B800 → B850 intra-LH2 energy transfer time was determined to be 1.3 ps for isolated LH2, which, upon aggregation in aqueous phase or clustering in chromatophores, shortened to 1.1 or 0.9 ps, respectively. The light-harvesting complex 1 (LH1) of this thermophilic purple sulfur bacterium contains bacteriochlorophyll a absorbing at 915 nm (B915), and the LH2(B850) → LH1(B915) intercomplex transfer time in chromatophores was found to be 6.6 ps. For chromatophores, a depolarization time of 21 ps was derived from the anisotropy kinetics of B850*, which is attributed to the migration of B850* excitation before being trapped by LH1. In addition, the B850* annihilation is accelerated upon LH2 aggregation in aqueous phase, but it is much less severe upon LH2 clustering in the intracytoplasmic membrane. These results are helpful in understanding the light-harvesting function of a bacterial photosynthetic membrane incorporating different types of antenna complexes.

Efficiency of porcine somatic cell nuclear transfer – a retrospective study of factors related to embryo recipient and embryos transferred

PubMed Central

Huang, Yongye; Ouyang, Hongsheng; Yu, Hao; Lai, Liangxue; Pang, Daxin; Li, Zhanjun

2013-01-01

Summary The successful generation of pigs via somatic cell nuclear transfer depends on reducing risk factors in several aspects. To provide an overview of some influencing factors related to embryo transfer, the follow-up data related to cloned pig production collected in our laboratory was examined. (i) Spring showed a higher full-term pregnancy rate compared with winter (33.6% vs 18.6%, P = 0.006). Furthermore, a regression equation can be drawn between full-term pregnancy numbers and pregnancy numbers in different months (y = 0.692x−3.326). (ii) There were no significant differences detected in the number of transferred embryos between surrogate sows exhibiting full-term development compared to those that did not. (iii) Non-ovulating surrogate sows presented a higher percentage of full-term pregnancies compared with ovulating sows (32.0% vs 17.5%, P = 0.004; respectively). (iv) Abortion was most likely to take place between Day 27 to Day 34. (v) Based on Life Table Survival Analysis, delivery in normally fertilized and surrogate sows is expected to be completed before Day 117 or Day 125, respectively. Additionally, the length of pregnancy in surrogate sows was negatively correlated with the average litter size, which was not found for normally fertilized sows. In conclusion, performing embryo transfer in appropriate seasons, improving the quality of embryos transferred, optimizing the timing of embryo transfer, limiting the occurrence of abortion, combined with ameliorating the management of delivery, is expected to result in the harvest of a great number of surviving cloned piglets. PMID:24244859

Acceleration of tropical cyclogenesis by self-aggregation feedbacks

NASA Astrophysics Data System (ADS)

Muller, Caroline J.; Romps, David M.

2018-03-01

Idealized simulations of tropical moist convection have revealed that clouds can spontaneously clump together in a process called self-aggregation. This results in a state where a moist cloudy region with intense deep convection is surrounded by extremely dry subsiding air devoid of deep convection. Because of the idealized settings of the simulations where it was discovered, the relevance of self-aggregation to the real world is still debated. Here, we show that self-aggregation feedbacks play a leading-order role in the spontaneous genesis of tropical cyclones in cloud-resolving simulations. Those feedbacks accelerate the cyclogenesis process by a factor of 2, and the feedbacks contributing to the cyclone formation show qualitative and quantitative agreement with the self-aggregation process. Once the cyclone is formed, wind-induced surface heat exchange (WISHE) effects dominate, although we find that self-aggregation feedbacks have a small but nonnegligible contribution to the maintenance of the mature cyclone. Our results suggest that self-aggregation, and the framework developed for its study, can help shed more light into the physical processes leading to cyclogenesis and cyclone intensification. In particular, our results point out the importance of the longwave radiative cooling outside the cyclone.

Perception of Transfer Climate Factors in the Macro and Micro Organizational Work Environment

ERIC Educational Resources Information Center

Diggs, Byron Kenneth

2011-01-01

This qualitative study was designed to provide insight on the perceived transfer climate factors in the macro and micro organizational work environment that may influence an employee's willingness to transfer what was learned in a training program to the job. More specifically, the purpose of the study was to delineate descriptive patterns and…

Minimal Model of Quantum Kinetic Clusters for the Energy-Transfer Network of a Light-Harvesting Protein Complex.

PubMed

Wu, Jianlan; Tang, Zhoufei; Gong, Zhihao; Cao, Jianshu; Mukamel, Shaul

2015-04-02

The energy absorbed in a light-harvesting protein complex is often transferred collectively through aggregated chromophore clusters. For population evolution of chromophores, the time-integrated effective rate matrix allows us to construct quantum kinetic clusters quantitatively and determine the reduced cluster-cluster transfer rates systematically, thus defining a minimal model of energy-transfer kinetics. For Fenna-Matthews-Olson (FMO) and light-havrvesting complex II (LCHII) monomers, quantum Markovian kinetics of clusters can accurately reproduce the overall energy-transfer process in the long-time scale. The dominant energy-transfer pathways are identified in the picture of aggregated clusters. The chromophores distributed extensively in various clusters can assist a fast and long-range energy transfer.

Light Scattering by Fractal Dust Aggregates. II. Opacity and Asymmetry Parameter

NASA Astrophysics Data System (ADS)

Tazaki, Ryo; Tanaka, Hidekazu

2018-06-01

Optical properties of dust aggregates are important at various astrophysical environments. To find a reliable approximation method for optical properties of dust aggregates, we calculate the opacity and the asymmetry parameter of dust aggregates by using a rigorous numerical method, the T-Matrix Method, and then the results are compared to those obtained by approximate methods: the Rayleigh–Gans–Debye (RGD) theory, the effective medium theory (EMT), and the distribution of hollow spheres method (DHS). First of all, we confirm that the RGD theory breaks down when multiple scattering is important. In addition, we find that both EMT and DHS fail to reproduce the optical properties of dust aggregates with fractal dimensions of 2 when the incident wavelength is shorter than the aggregate radius. In order to solve these problems, we test the mean field theory (MFT), where multiple scattering can be taken into account. We show that the extinction opacity of dust aggregates can be well reproduced by MFT. However, it is also shown that MFT is not able to reproduce the scattering and absorption opacities when multiple scattering is important. We successfully resolve this weak point of MFT, by newly developing a modified mean field theory (MMF). Hence, we conclude that MMF can be a useful tool to investigate radiative transfer properties of various astrophysical environments. We also point out an enhancement of the absorption opacity of dust aggregates in the Rayleigh domain, which would be important to explain the large millimeter-wave opacity inferred from observations of protoplanetary disks.

THE REBOUND CONDITION OF DUST AGGREGATES REVEALED BY NUMERICAL SIMULATION OF THEIR COLLISIONS

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

Wada, Koji; Tanaka, Hidekazu; Yamamoto, Tetsuo

2011-08-10

Collisional growth of dust aggregates is a plausible root of planetesimals forming in protoplanetary disks. However, a rebound of colliding dust aggregates prevents dust from growing into planetesimals. In fact, rebounding aggregates are observed in laboratory experiments but not in previous numerical simulations. Therefore, the condition of rebound between dust aggregates should be clarified to better understand the processes of dust growth and planetesimal formation. We have carried out numerical simulations of aggregate collisions for various types of aggregates and succeeded in reproducing a rebound of colliding aggregates under specific conditions. Our finding is that in the rebound process, themore » key factor of the aggregate structure is the coordination number, namely, the number of particles in contact with a particle. A rebound is governed by the energy dissipation along with restructuring of the aggregates and a large coordination number inhibits the restructuring at collisions. Results of our numerical simulation for various aggregates indicate that they stick to each other when the mean coordination number is less than 6, regardless of their materials and structures, as long as their collision velocity is less than the critical velocity for fragmentation. This criterion of the coordination number would correspond to a filling factor of {approx}0.3, which is somewhat larger than that reported in laboratory experiments. In protoplanetary disks, dust aggregates are expected to have low bulk densities (<0.1 g cm{sup -3}) during their growth, which would prevent dust aggregates from rebounding. This result supports the formation of planetesimals with direct dust growth in protoplanetary disks.« less

Enhanced Luminescent Stability through Particle Interactions in Silicon Nanocrystal Aggregates

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

Miller, Joseph B.; Dandu, Naveen; Velizhanin, Kirill A.

2015-10-27

Close-packed assemblies of ligand-passivated colloidal nanocrystals can exhibit enhanced photoluminescent stability, but the origin of this effect is unclear. Here, we use experiment, simulation, and ab initio computation to examine the influence of interparticle interactions on the photoluminescent stability of silicon nanocrystal aggregates. The time-dependent photoluminescence emitted by structures ranging in size from a single quantum dot to agglomerates of more than a thousand is compared with Monte Carlo simulations of noninteracting ensembles using measured single-particle blinking data as input. In contrast to the behavior typically exhibited by the metal chalcogenides, the measured photoluminescent stability shows an enhancement with respectmore » to the noninteracting scenario with increasing aggregate size. We model this behavior using time-dependent density functional theory calculations of energy transfer between neighboring nanocrystals as a function of nanocrystal size, separation, and the presence of charge and/or surface-passivation defects. Our results suggest that rapid exciton transfer from “bright” nanocrystals to surface trap states in nearest-neighbors can efficiently fill such traps and enhance the stability of emission by promoting the radiative recombination of slowly diffusing excited electrons.« less

Fabrication of Polymeric Micelles with Aggregation-Induced Emission and Forster Resonance Energy Transfer for Anticancer Drug Delivery.

PubMed

Hao, Na; Sun, Changzhen; Wu, Zhengfei; Xu, Long; Gao, Wenxia; Cao, Jun; Li, Li; He, Bin

2017-07-19

With the aim of obtaining effective cancer therapy with simultaneous cellular imaging, dynamic drug-release monitoring, and chemotherapeutic treatment, a polymeric micelle with aggregation-induced emission (AIE) imaging and a Forster resonance energy transfer (FRET) effect was fabricated as the drug carrier. An amphiphilic conjugate of 1H-pyrrole-1-propanoicacid (MAL)-poly(ethylene glycol) (PEG)-Tripp-bearing AIE molecules were synthesized and self-assembled into micelles to load the anticancer drug doxorubicin (DOX). Spherical DOX-loaded micelles with the mean size of 106 nm were obtained with good physiological stability (CMC, 12.5 μg/mL), high drug-loading capacity (10.4%), and encapsulation efficiency (86%). The cellular uptake behavior of DOX-loaded MAL-PEG-Tripp micelles was visible for high-quality intracellular imaging due to the AIE property. The delivery of DOX from the drug-loaded micelles was dynamic monitored by the FRET effect between the DOX and MAL-PEG-Tripp. Both in vitro (IC50, 2.36 μg/mL) and in vivo anticancer activity tests revealed that the DOX-loaded MAL-PEG-Tripp micelles exhibited promising therapeutic efficacy to cancer with low systematic toxicity. In summary, this micelle provided an effective way to fabricate novel nanoplatform for intracellular imaging, drug-delivery tracing, and chemotherapy.

Azaphilones inhibit tau aggregation and dissolve tau aggregates in vitro.

PubMed

Paranjape, Smita R; Riley, Andrew P; Somoza, Amber D; Oakley, C Elizabeth; Wang, Clay C C; Prisinzano, Thomas E; Oakley, Berl R; Gamblin, T Chris

2015-05-20

The aggregation of the microtubule-associated protein tau is a seminal event in many neurodegenerative diseases, including Alzheimer's disease. The inhibition or reversal of tau aggregation is therefore a potential therapeutic strategy for these diseases. Fungal natural products have proven to be a rich source of useful compounds having wide varieties of biological activities. We have previously screened Aspergillus nidulans secondary metabolites for their ability to inhibit tau aggregation in vitro using an arachidonic acid polymerization protocol. One aggregation inhibitor identified was asperbenzaldehyde, an intermediate in azaphilone biosynthesis. We therefore tested 11 azaphilone derivatives to determine their tau assembly inhibition properties in vitro. All compounds tested inhibited tau filament assembly to some extent, and four of the 11 compounds had the advantageous property of disassembling preformed tau aggregates in a dose-dependent fashion. The addition of these compounds to the tau aggregates reduced both the total length and number of tau polymers. The most potent compounds were tested in in vitro reactions to determine whether they interfere with tau's normal function of stabilizing microtubules (MTs). We found that they did not completely inhibit MT assembly in the presence of tau. These derivatives are very promising lead compounds for tau aggregation inhibitors and, more excitingly, for compounds that can disassemble pre-existing tau filaments. They also represent a new class of anti-tau aggregation compounds with a novel structural scaffold.

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.

The Reverse Transfer Student: A Growing Factor in Higher Education

ERIC Educational Resources Information Center

Brimm, Jack; Achilles, C. M.

1976-01-01

A study of 195 reverse transfer students showed that following a poor academic performance at the university, the students achieved satisfactorily at the two-year college. Students who later returned to the university improved their grades with each quarter's course work. Factors associated with academic performance at the two institutions are…

Factors Associated with Transfer of Training in Workplace E-Learning

ERIC Educational Resources Information Center

Park, Ji-Hye; Wentling, Tim

2007-01-01

Purpose--The purpose of this study is to investigate the effect of factors associated with e-learning, particularly computer attitudes and usability, on transfer of training in workplace e-learning courses. Design/methodology/approach--This study relied on quantitative data obtained from four online survey questionnaires. The sample of this study…

The effect of nanoparticles aggregation on the thermal conductivity of nanofluids at very low concentrations: Experimental and theoretical evaluations

NASA Astrophysics Data System (ADS)

Motevasel, Mohsen; Nazar, Ali Reza Solaimany; Jamialahmadi, Mohammad

2018-01-01

Nanoparticles suspended in a base fluid yield increased thermal conductivity, which in turn increases convection heat transfer rate. Prediction of suitable relations for determination of thermal conductivity results in heightened accuracy in the calculation of convection heat transfer coefficient and reduced costs. In the majority of studies performed on the prediction of thermal conductivity, some relations and models were used in which the effect of aggregation of particles, especially at low concentrations was ignored. In this research, the thermal conductivity of the nanofluid is measured experimentally at low volumetric concentrations, within the range of 0.02-0.2% for the nanoparticles of Al2O3, MgO, CuO, and SiC in the base fluid of distilled water. The results obtained from the models are compared by the available models considering and neglecting the effect of aggregation of particles. Within the range of the applied concentrations, the relative absolute average deviation ratio of the thermal conductivity models without considering the aggregation effect in relation with the models considering the aggregate, is observed to be between 2 and 6 times. Therefore, it is recommended that even at low concentrations, the effect of aggregation should be considered in the prediction of thermal conductivity.

Uncoupling of Protein Aggregation and Neurodegeneration in a Mouse Amyotrophic Lateral Sclerosis Model.

PubMed

Lee, Joo-Yong; Kawaguchi, Yoshiharu; Li, Ming; Kapur, Meghan; Choi, Su Jin; Kim, Hak-June; Park, Song-Yi; Zhu, Haining; Yao, Tso-Pang

2015-01-01

Aberrant accumulation of protein aggregates is a pathological hallmark of many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Although a buildup of protein aggregates frequently leads to cell death, whether it is the key pathogenic factor in driving neurodegenerative disease remains controversial. HDAC6, a cytosolic ubiquitin-binding deacetylase, has emerged as an important regulator of ubiquitin-dependent quality control autophagy, a lysosome-dependent degradative system responsible for the disposal of misfolded protein aggregates and damaged organelles. Here, we show that in cell models HDAC6 plays a protective role against multiple disease-associated and aggregation-prone cytosolic proteins by facilitating their degradation. We further show that HDAC6 is required for efficient localization of lysosomes to protein aggregates, indicating that lysosome targeting to autophagic substrates is regulated. Supporting a critical role of HDAC6 in protein aggregate disposal in vivo, genetic ablation of HDAC6 in a transgenic SOD1G93A mouse, a model of ALS, leads to dramatic accumulation of ubiquitinated SOD1G93A protein aggregates. Surprisingly, despite a robust buildup of SOD1G93A aggregates, deletion of HDAC6 only moderately modified the motor phenotypes. These findings indicate that SOD1G93A aggregation is not the only determining factor to drive neurodegeneration in ALS, and that HDAC6 likely modulates neurodegeneration through additional mechanisms beyond protein aggregate clearance. © 2015 S. Karger AG, Basel.

Soil-to-crop transfer factors of tellurium.

PubMed

Yang, Guosheng; Zheng, Jian; Tagami, Keiko; Uchida, Shigeo

2014-09-01

Stable tellurium (Te) concentrations in 148 sets of agricultural soil and associated crop samples were measured in this study to obtain soil-to-crop transfer factor (TF) of Te. We used a recently developed simple method that applies digestion of samples with aqua regia and sector field inductively coupled plasma mass spectrometry to measure low Te levels in these samples. Geometric mean (GM) concentrations of Te in soil and crops were 75μgkg(-1)-dry (range: 15-850μgkg(-1)-dry) and 1.8μgkg(-1)-dry (range: 0.1-120μgkg(-1)-dry), respectively; the Te concentration range was significantly wider in crops than in soil. Using these data, we calculated TFs and obtained their range from 1.3×10(-3) to 1.1×10(-1). The GM of TF for upland field crops was calculated to be 2.0×10(-2) and for brown rice was 3.1×10(-2); all crop types had the similar GMs of their TF values. Data comparison for TF of Te was carried out with six elements, which are present in anionic forms in soil environment like Te is, i.e. P, Br, As, Se, Mo, and I. TFs of Te and I showed the highest correlation factor for upland field crops by t-test (r=0.577, p<0.001), but no correlation was found for brown rice. We considered it likely that different water management practices in upland fields and paddy fields affected the Te transfer from soil to crops. Copyright © 2014 Elsevier Ltd. All rights reserved.

Familial aggregation of attention-deficit/hyperactivity disorder.

PubMed

Chen, Qi; Brikell, Isabell; Lichtenstein, Paul; Serlachius, Eva; Kuja-Halkola, Ralf; Sandin, Sven; Larsson, Henrik

2017-03-01

Attention-deficit/hyperactivity disorder (ADHD) aggregates in families. To date, the strength, pattern, and characteristics of the familial aggregation have not been thoroughly assessed in a population-based family sample. In this cohort study, we identified relative pairs of twins, full and half-siblings, and full and half cousins from 1,656,943 unique individuals born in Sweden between 1985 and 2006. The relatives of index persons were followed from their third birthday to 31 December 2009 for ADHD diagnosis. Birth year adjusted hazard ratio (HR), that is, the rate of ADHD in relatives of ADHD-affected index persons compared with the rate of ADHD in relatives of unaffected index persons, was estimated in the different types of relatives using Cox proportional hazards model. During the follow-up, 31,865 individuals were diagnosed with ADHD (male to female ratio was 3.7). The birth year adjusted HRs were as follows: 70.45 for monozygotic twins; 8.44 for dizygotic twins; 8.27 for full siblings; 2.86 for maternal half-siblings; 2.31 for paternal half-siblings; 2.24 for full cousins; 1.47 for half cousins. Maternal half-siblings had significantly higher HR than in paternal half-siblings. The HR did not seem to be affected by index person's sex. Full siblings of index persons with ADHD diagnosis present at age 18 or older had a higher rate of ADHD (HR: 11.49) than full siblings of index persons with ADHD diagnosis only before age 18 (HR: 4.68). Familial aggregation of ADHD increases with increasing genetic relatedness. The familial aggregation is driven by not only genetic factors but also a small amount of shared environmental factors. Persistence of ADHD into adulthood indexes stronger familial aggregation of ADHD. © 2016 Association for Child and Adolescent Mental Health.

Marine Synechococcus Aggregation

NASA Astrophysics Data System (ADS)

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

2016-02-01

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

Exploring the early steps of amyloid peptide aggregation by computers.

PubMed

Mousseau, Normand; Derreumaux, Philippe

2005-11-01

The assembly of normally soluble proteins into amyloid fibrils is a hallmark of neurodegenerative diseases. Because protein aggregation is very complex, involving a variety of oligomeric metastable intermediates, the detailed aggregation paths and structural characterization of the intermediates remain to be determined. Yet, there is strong evidence that these oligomers, which form early in the process of fibrillogenesis, are cytotoxic. In this paper, we review our current understanding of the underlying factors that promote the aggregation of peptides into amyloid fibrils. We focus here on the structural and dynamic aspects of the aggregation as observed in state-of-the-art computer simulations of amyloid-forming peptides with an emphasis on the activation-relaxation technique.

Inferring Aggregated Functional Traits from Metagenomic Data Using Constrained Non-negative Matrix Factorization: Application to Fiber Degradation in the Human Gut Microbiota.

PubMed

Raguideau, Sébastien; Plancade, Sandra; Pons, Nicolas; Leclerc, Marion; Laroche, Béatrice

2016-12-01

Whole Genome Shotgun (WGS) metagenomics is increasingly used to study the structure and functions of complex microbial ecosystems, both from the taxonomic and functional point of view. Gene inventories of otherwise uncultured microbial communities make the direct functional profiling of microbial communities possible. The concept of community aggregated trait has been adapted from environmental and plant functional ecology to the framework of microbial ecology. Community aggregated traits are quantified from WGS data by computing the abundance of relevant marker genes. They can be used to study key processes at the ecosystem level and correlate environmental factors and ecosystem functions. In this paper we propose a novel model based approach to infer combinations of aggregated traits characterizing specific ecosystemic metabolic processes. We formulate a model of these Combined Aggregated Functional Traits (CAFTs) accounting for a hierarchical structure of genes, which are associated on microbial genomes, further linked at the ecosystem level by complex co-occurrences or interactions. The model is completed with constraints specifically designed to exploit available genomic information, in order to favor biologically relevant CAFTs. The CAFTs structure, as well as their intensity in the ecosystem, is obtained by solving a constrained Non-negative Matrix Factorization (NMF) problem. We developed a multicriteria selection procedure for the number of CAFTs. We illustrated our method on the modelling of ecosystemic functional traits of fiber degradation by the human gut microbiota. We used 1408 samples of gene abundances from several high-throughput sequencing projects and found that four CAFTs only were needed to represent the fiber degradation potential. This data reduction highlighted biologically consistent functional patterns while providing a high quality preservation of the original data. Our method is generic and can be applied to other metabolic processes in

An Aß concatemer with altered aggregation propensities.

PubMed

Giehm, L; Dal Degan, F; Fraser, P; Klysner, S; Otzen, Daniel E

2010-10-01

We present an analysis of the conformational and aggregative properties of an Aß concatemer (Con-Alz) of interest for vaccine development against Alzheimer's disease. Con-Alz consists of 3 copies of the 43 residues of the Aß peptide separated by the P2 and P30 T-cell epitopes from the tetanus toxin. Even in the presence of high concentrations of denaturants or fluorinated alcohols, Con-Alz has a very high propensity to form aggregates which slowly coalesce over time with changes in secondary, tertiary and quaternary structure. Only micellar concentrations of SDS were able to inhibit aggregation. The increase in the ability to bind the fibril-binding dye ThT increases without lag time, which is characteristic of relatively amorphous aggregates. Confirming this, electron microscopy reveals that Con-Alz adopts a morphology resembling truncated protofibrils after prolonged incubation, but it is unable to assemble into classical amyloid fibrils. Despite its high propensity to aggregate, Con-Alz does not show any significant ability to permeabilize vesicles, which for fibrillating proteins is taken to be a key factor in aggregate cytotoxicity and is attributed to oligomers formed at an early stage in the fibrillation process. Physically linking multiple copies of the Aß-peptide may thus sterically restrict Con-Alz against forming cytotoxic oligomers, forcing it instead to adopt a less well-organized assembly of intermeshed polypeptide chains. Copyright © 2010 Elsevier B.V. All rights reserved.

The ultrasonic-enhanced factor of mass-transfer coefficient in the supercritical carbon dioxide extraction

NASA Astrophysics Data System (ADS)

Luo, Benyi; Lu, Yigang

2008-10-01

Based on several hypotheses about the process of supercritical carbon dioxide extraction, the onflow around the solute granule is figured out by the Navier-Stocks equation. In combination with the Higbie’s solute infiltration model, the link between the mass-transfer coefficient and the velocity of flow is found. The mass-transfer coefficient with the ultrasonical effect is compared with that without the ultrasonical effect, and then a new parameter named the ultrasonic-enhanced factor of mass-transfer coefficient is brought forward, which describes the mathematical model of the supercritical carbon dioxide extraction process enhanced by ultrasonic. The model gives out the relationships among the ultrasonical power, the ultrasonical frequency, the radius of solute granule and the ultrasonic-enhanced factor of mass-transfer coefficient. The results calculated by this model fit well with the experimental data, including the extraction of Coix Lacryma-jobi Seed Oil (CLSO) and Coix Lacryma-jobi Seed Ester (CLSE) from coix seeds and the extraction of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) from the alga by means of the ultrasonic-enhanced supercritical carbon dioxide extraction (USFE) and the supercritical carbon dioxide extraction (SFE) respectively. This proves the rationality of the ultrasonic-enhanced factor model. The model provides a theoretical basis for the application of ultrasonic-enhanced supercritical fluid extraction technique.

Microbial Ecology of Soil Aggregation in Agroecosystems

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Energy transfer between a nanosystem and its host fluid: A multiscale factorization approach

NASA Astrophysics Data System (ADS)

Sereda, Yuriy V.; Espinosa-Duran, John M.; Ortoleva, Peter J.

2014-02-01

Energy transfer between a macromolecule or supramolecular assembly and a host medium is considered from the perspective of Newton's equations and Lie-Trotter factorization. The development starts by demonstrating that the energy of the molecule evolves slowly relative to the time scale of atomic collisions-vibrations. The energy is envisioned to be a coarse-grained variable that coevolves with the rapidly fluctuating atomistic degrees of freedom. Lie-Trotter factorization is shown to be a natural framework for expressing this coevolution. A mathematical formalism and workflow for efficient multiscale simulation of energy transfer is presented. Lactoferrin and human papilloma virus capsid-like structure are used for validation.

Environmental factors influencing gene transfer agent (GTA) mediated transduction in the subtropical ocean.

PubMed

McDaniel, Lauren D; Young, Elizabeth C; Ritchie, Kimberly B; Paul, John H

2012-01-01

Microbial genomic sequence analyses have indicated widespread horizontal gene transfer (HGT). However, an adequate mechanism accounting for the ubiquity of HGT has been lacking. Recently, high frequencies of interspecific gene transfer have been documented, catalyzed by Gene Transfer Agents (GTAs) of marine α-Proteobacteria. It has been proposed that the presence of bacterial genes in highly purified viral metagenomes may be due to GTAs. However, factors influencing GTA-mediated gene transfer in the environment have not yet been determined. Several genomically sequenced strains containing complete GTA sequences similar to Rhodobacter capsulatus (RcGTA, type strain) were screened to ascertain if they produced putative GTAs, and at what abundance. Five of nine marine strains screened to date spontaneously produced virus-like particles (VLP's) in stationary phase. Three of these strains have demonstrated gene transfer activity, two of which were documented by this lab. These two strains Roseovarius nubinhibens ISM and Nitratireductor 44B9s, were utilized to produce GTAs designated RnGTA and NrGTA and gene transfer activity was verified in culture. Cell-free preparations of purified RnGTA and NrGTA particles from marked donor strains were incubated with natural microbial assemblages to determine the level of GTA-mediated gene transfer. In conjunction, several ambient environmental parameters were measured including lysogeny indicated by prophage induction. GTA production in culture systems indicated that approximately half of the strains produced GTA-like particles and maximal GTA counts ranged from 10-30% of host abundance. Modeling of GTA-mediated gene transfer frequencies in natural samples, along with other measured environmental variables, indicated a strong relationship between GTA mediated gene transfer and the combined factors of salinity, multiplicity of infection (MOI) and ambient bacterial abundance. These results indicate that GTA-mediated HGT in the

Environmental Factors Influencing Gene Transfer Agent (GTA) Mediated Transduction in the Subtropical Ocean

PubMed Central

McDaniel, Lauren D.; Young, Elizabeth C.; Ritchie, Kimberly B.; Paul, John H.

2012-01-01

Microbial genomic sequence analyses have indicated widespread horizontal gene transfer (HGT). However, an adequate mechanism accounting for the ubiquity of HGT has been lacking. Recently, high frequencies of interspecific gene transfer have been documented, catalyzed by Gene Transfer Agents (GTAs) of marine α-Proteobacteria. It has been proposed that the presence of bacterial genes in highly purified viral metagenomes may be due to GTAs. However, factors influencing GTA-mediated gene transfer in the environment have not yet been determined. Several genomically sequenced strains containing complete GTA sequences similar to Rhodobacter capsulatus (RcGTA, type strain) were screened to ascertain if they produced putative GTAs, and at what abundance. Five of nine marine strains screened to date spontaneously produced virus-like particles (VLP's) in stationary phase. Three of these strains have demonstrated gene transfer activity, two of which were documented by this lab. These two strains Roseovarius nubinhibens ISM and Nitratireductor 44B9s, were utilized to produce GTAs designated RnGTA and NrGTA and gene transfer activity was verified in culture. Cell-free preparations of purified RnGTA and NrGTA particles from marked donor strains were incubated with natural microbial assemblages to determine the level of GTA-mediated gene transfer. In conjunction, several ambient environmental parameters were measured including lysogeny indicated by prophage induction. GTA production in culture systems indicated that approximately half of the strains produced GTA-like particles and maximal GTA counts ranged from 10–30% of host abundance. Modeling of GTA-mediated gene transfer frequencies in natural samples, along with other measured environmental variables, indicated a strong relationship between GTA mediated gene transfer and the combined factors of salinity, multiplicity of infection (MOI) and ambient bacterial abundance. These results indicate that GTA-mediated HGT in the

GEOMETRIC CROSS SECTIONS OF DUST AGGREGATES AND A COMPRESSION MODEL FOR AGGREGATE COLLISIONS

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

Suyama, Toru; Wada, Koji; Tanaka, Hidekazu

2012-07-10

Geometric cross sections of dust aggregates determine their coupling with disk gas, which governs their motions in protoplanetary disks. Collisional outcomes also depend on geometric cross sections of initial aggregates. In a previous paper, we performed three-dimensional N-body simulations of sequential collisions of aggregates composed of a number of sub-micron-sized icy particles and examined radii of gyration (and bulk densities) of the obtained aggregates. We showed that collisional compression of aggregates is not efficient and that aggregates remain fluffy. In the present study, we examine geometric cross sections of the aggregates. Their cross sections decrease due to compression as wellmore » as to their gyration radii. It is found that a relation between the cross section and the gyration radius proposed by Okuzumi et al. is valid for the compressed aggregates. We also refine the compression model proposed in our previous paper. The refined model enables us to calculate the evolution of both gyration radii and cross sections of growing aggregates and reproduces well our numerical results of sequential aggregate collisions. The refined model can describe non-equal-mass collisions as well as equal-mass cases. Although we do not take into account oblique collisions in the present study, oblique collisions would further hinder compression of aggregates.« less

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

NASA Astrophysics Data System (ADS)

Chaiyarit, Sakdithep; Thongboonkerd, Visith

2017-12-01

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

A new efficient method for calculation of Frenkel exciton parameters in molecular aggregates

NASA Astrophysics Data System (ADS)

Plötz, Per-Arno; Niehaus, Thomas; Kühn, Oliver

2014-05-01

The Frenkel exciton Hamiltonian is at the heart of many simulations of excitation energy transfer in molecular aggregates. It separates the aggregate into Coulomb-coupled monomers. Here it is shown that the respective parameters, i.e., monomeric excitation energies and Coulomb couplings between transition densities can be efficiently calculated using time-dependent tight-binding-based density functional theory (TD-DFTB). Specifically, Coulomb couplings are expressed in terms of self-consistently determined Mulliken transition charges. The approach is applied to two dimer systems. First, formaldehyde oxime for which a detailed comparison with standard DFT using the B3LYP and the PBE functionals as well as with SCS-CC2 is provided. Second, the Coulomb coupling is explored in dependence on the intermolecular coordinates for a perylene bisimide dimer. This provides structural evidence for the previously observed biphasic aggregation behavior of this dye.

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

DOT National Transportation Integrated Search

2015-06-01

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

Conformational stability as a design target to control protein aggregation.

PubMed

Costanzo, Joseph A; O'Brien, Christopher J; Tiller, Kathryn; Tamargo, Erin; Robinson, Anne Skaja; Roberts, Christopher J; Fernandez, Erik J

2014-05-01

Non-native protein aggregation is a prevalent problem occurring in many biotechnological manufacturing processes and can compromise the biological activity of the target molecule or induce an undesired immune response. Additionally, some non-native aggregation mechanisms lead to amyloid fibril formation, which can be associated with debilitating diseases. For natively folded proteins, partial or complete unfolding is often required to populate aggregation-prone conformational states, and therefore one proposed strategy to mitigate aggregation is to increase the free energy for unfolding (ΔGunf) prior to aggregation. A computational design approach was tested using human γD crystallin (γD-crys) as a model multi-domain protein. Two mutational strategies were tested for their ability to reduce/increase aggregation rates by increasing/decreasing ΔGunf: stabilizing the less stable domain and stabilizing the domain-domain interface. The computational protein design algorithm, RosettaDesign, was implemented to identify point variants. The results showed that although the predicted free energies were only weakly correlated with the experimental ΔGunf values, increased/decreased aggregation rates for γD-crys correlated reasonably well with decreases/increases in experimental ΔGunf, illustrating improved conformational stability as a possible design target to mitigate aggregation. However, the results also illustrate that conformational stability is not the sole design factor controlling aggregation rates of natively folded proteins.

Factors affecting the efficiency of foal production in a commercial oocyte transfer program.

PubMed

Riera, Fernando L; Roldán, Jaime E; Gomez, José; Hinrichs, Katrin

2016-04-01

Transfer of donor oocytes to the oviducts of inseminated recipient mares (oocyte transfer, OT) presents a valuable method for production of foals from otherwise infertile mares. Little information is available, however, on factors affecting success of OT in a clinical setting. We report the findings over three breeding seasons in a commercial OT program developed at an equine embryo transfer center in Argentina. Overall, 25 mares were enrolled, and 197 follicle aspiration procedures were performed. The average mare age was 23 years. Follicle aspiration was performed with a needle placed through the flank; the oocyte recovery rate per follicle aspirated was 149 of 227 (66%). Induction of donor ovulation with deslorelin + hCG resulted in a significantly higher oocyte recovery rate than did induction with deslorelin alone (75% vs. 58%). There was no significant effect of mare age (17-20, 21-24, or 25-27 years) on oocyte recovery rate. Twelve oocytes were degenerating or lost during handling; transfer of the remaining 137 oocytes resulted in 42 pregnancies (31%) at 14 days. Of these, 32 (23% per transfer) went on to produce a foal or ongoing pregnancy. Transfer of oocytes recovered with a compact cumulus, without donor follicle induction, or less than 20 hours after induction was associated with a significantly reduced pregnancy rate (1/16, 6%), as was use of noncycling, hormone-treated recipients (2/22, 9%). To evaluate management factors affecting pregnancy rate, noncycling, hormone-treated recipients were disregarded, and only procedures using mature (expanded cumulus) oocytes recovered and transferred on the standard schedule (n = 99) were included. Mare age did not significantly affect rates of pregnancy or pregnancy loss. Similar pregnancy rates were obtained using recipients inseminated from 1 to 27 hours before transfer. Counterintuitively, insemination of recipients immediately (1-2 hours) after aspiration of the recipient follicle was associated with a high

Self-organization of intertidal snails facilitates evolution of aggregation behavior.

PubMed

Stafford, Richard; Davies, Mark S; Williams, Gray A

2008-01-01

Many intertidal snails form aggregations during emersion to minimize desiccation stress. Here we investigate possible mechanisms for the evolution of such behavior. Two behavioral traits (following of mucus trails, and crevice occupation), which both provide selective advantages to individuals that possess the traits over individuals that do not, result in self-organization of aggregations in crevices in the rock surface. We suggest that the existence of self-organizing aggregations provides a mechanism by which aggregation behavior can evolve. The inclusion of an explicitly coded third behavior, aggregation, in a simulated population produces patterns statistically similar to those found on real rocky shores. Allowing these three behaviors to evolve using an evolutionary algorithm, however, results in aggregation behavior being selected against on shores with high crevice density. The inclusion of broadcast spawning dispersal mechanisms in the simulation, however, results in aggregation behavior evolving as predicted on shores with both high crevice density and low crevice density (evolving in crevices first, and then both in crevices and on flat rock), indicating the importance of environmental interactions in understanding evolutionary processes. We propose that self-organization can be an important factor in the evolution of group behaviors.

Transfer factor - hypotheses for its structure and function.

PubMed

Shifrine, M; Scibienski, R

1975-01-01

Transfer factor (TF) is a dialyzable extract from primed lymphocytes that is able to transfer specific delayed hypersensitivity from one animal to another. On the basis of available data we suggest that TF is a polypeptide with a molecular weight below 15,000 daltons. We hypothesize that TF is the variable light or heavy chain domain of immunoglobulin: such a molecule conforms with the accepted properties of TF and also has the necessary specificity requirements. We also hypothesize that TF is part of a receptor site. beta-2-microglobulin, a molecule that is an integral part of cell surfaces, could be the anchor for TF. beta-2-microglobulin has homologies with the constant portion of immunoglobulin light or heavy chain and thus would combine with the variable domain (TF) to form a complete receptor site for a specific antigen. The properties of TF suggest its mode of action, which is discussed in detail in the text. The biologic advantages of TF is its ability to confer immediate (immunologie specific) protection while the 'normal' immune response develops.

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.

Exciton Level Structure and Dynamics in Tubular Porphyrin Aggregates

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

Wan, Yan; Stradomska, Anna; Fong, Sarah

2014-10-30

We present an account of the optical properties of the Frenkel excitons in self-assembled porphyrin tubular aggregates that represent an analog to natural photosynthetic antennae. Using a combination of ultrafast optical spectroscopy and stochastic exciton modeling, we address both linear and nonlinear exciton absorption, relaxation pathways, and the role of disorder. The static disorder-dominated absorption and fluorescence line widths show little temperature dependence for the lowest excitons (Q band), which we successfully simulate using a model of exciton scattering on acoustic phonons in the host matrix. Temperature-dependent transient absorption of and fluorescence from the excitons in the tubular aggregates aremore » marked by nonexponential decays with time scales ranging from a few picoseconds to a few nanoseconds, reflecting complex relaxation mechanisms. Combined experimental and theoretical investigations indicate that nonradiative pathways induced by traps and defects dominate the relaxation of excitons in the tubular aggregates. We model the pumpprobe spectra and ascribe the excited-state absorption to transitions from one-exciton states to a manifold of mixed one- and two-exciton states. Our results demonstrate that while the delocalized Frenkel excitons (over 208 (1036) molecules for the optically dominant excitons in the Q (B) band) resulting from strong intermolecular coupling in these aggregates could potentially facilitate efficient energy transfer, fast relaxation due to defects and disorder probably present a major limitation for exciton transport over large distances.« less

On cooperative effects and aggregation of GNNQQNY and NNQQNY peptides

NASA Astrophysics Data System (ADS)

Nochebuena, Jorge; Ireta, Joel

2015-10-01

Some health disturbances like neurodegenerative diseases are associated to the presence of amyloids. GNNQQNY and NNQQNY peptides are considered as prototypical examples for studying the formation of amyloids. These exhibit quite different aggregation behaviors despite they solely differ in size by one residue. To get insight into the reasons for such difference, we have examined association energies of aggregates (parallel β-sheets, fibril-spines, and crystal structures) from GNNQQNY and NNQQY using density functional theory. As we found that GNNQQNY tends to form a zwitterion in the crystal structure, we have investigated the energetics of parallel β-sheets and fibril-spines in the canonical and zwitterionic states. We found that the formation of GNNQQNY aggregates is energetically more favored than the formation of the NNQQNY ones. We show that the latter is connected to the network of hydrogen bonds formed by each aggregate. Moreover, we found that the formation of some NNQQNY aggregates is anticooperative, whereas cooperative with GNNQQNY. These results have interesting implications for deciphering the factors determining peptide aggregation propensities.

Assessment and validation of the community radiative transfer model for ice cloud conditions

NASA Astrophysics Data System (ADS)

Yi, Bingqi; Yang, Ping; Weng, Fuzhong; Liu, Quanhua

2014-11-01

The performance of the Community Radiative Transfer Model (CRTM) under ice cloud conditions is evaluated and improved with the implementation of MODIS collection 6 ice cloud optical property model based on the use of severely roughened solid column aggregates and a modified Gamma particle size distribution. New ice cloud bulk scattering properties (namely, the extinction efficiency, single-scattering albedo, asymmetry factor, and scattering phase function) suitable for application to the CRTM are calculated by using the most up-to-date ice particle optical property library. CRTM-based simulations illustrate reasonable accuracy in comparison with the counterparts derived from a combination of the Discrete Ordinate Radiative Transfer (DISORT) model and the Line-by-line Radiative Transfer Model (LBLRTM). Furthermore, simulations of the top of the atmosphere brightness temperature with CRTM for the Crosstrack Infrared Sounder (CrIS) are carried out to further evaluate the updated CRTM ice cloud optical property look-up table.

Neuroforecasting Aggregate Choice

PubMed Central

Knutson, Brian; Genevsky, Alexander

2018-01-01

Advances in brain-imaging design and analysis have allowed investigators to use neural activity to predict individual choice, while emerging Internet markets have opened up new opportunities for forecasting aggregate choice. Here, we review emerging research that bridges these levels of analysis by attempting to use group neural activity to forecast aggregate choice. A survey of initial findings suggests that components of group neural activity might forecast aggregate choice, in some cases even beyond traditional behavioral measures. In addition to demonstrating the plausibility of neuroforecasting, these findings raise the possibility that not all neural processes that predict individual choice forecast aggregate choice to the same degree. We propose that although integrative choice components may confer more consistency within individuals, affective choice components may generalize more broadly across individuals to forecast aggregate choice. PMID:29706726

Natural convection during heat accumulation by substances with change of aggregate state

NASA Astrophysics Data System (ADS)

Chukayev, A. G.; Kuks, A. M.

1985-03-01

Heat transfer calculations are presented for a heat accumulator using the melting heat of a substance which changes its state of aggregation. It is shown that the approach adopted here makes it possible to evaluate the efficiency of using heat-storage materials in the pipe-tank system. The calculations, which allow for the effect of free convection in the liquid phase, have been made using the Boussinesq approximation. Results of a numerical experiment for NaNO3 salt show that the effect of natural convection on heat transfer is significant and that the heat flux to the material decreases as heat accumulates.

Protein aggregates as depots for the release of biologically active compounds.

PubMed

Artemova, Natalya V; Kasakov, Alexei S; Bumagina, Zoya M; Lyutova, Elena M; Gurvits, Bella Ya

2008-12-12

Protein misfolding and aggregation is one of the most serious problems in cell biology, molecular medicine, and biotechnology. Misfolded proteins interact with each other or with other proteins in non-productive or damaging ways. However, a new paradigm arises that protein aggregation may be exploited by nature to perform specific functions in different biological contexts. From this consideration, acceleration of stress-induced protein aggregation triggered by any factor resulting in the formation of soluble aggregates may have paradoxical positive consequences. Here, we suggest that amorphous aggregates can act as a source for the release of biologically active proteins after removal of stress conditions. To address this concept, we investigated the kinetics of thermal aggregation in vitro of yeast alcohol dehydrogenase (ADH) as a model substrate in the presence of two amphiphilic peptides: Arg-Phe or Ala-Phe-Lys. Using dynamic light scattering (DLS) and turbidimetry, we have demonstrated that under mild stress conditions the concentration-dependent acceleration of ADH aggregation by these peptides results in formation of large but soluble complexes of proteins prone to refolding.

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

Aggregate stability is an important factor in soil resistance against erosion, and, by influencing the extent of sediment transport associated with surface runoff, it is thus also one of the key factors which determine on- and off-site effects of water erosion. As it strongly depends on soil organic matter, many studies have explored how aggregate stability can be improved by organic matter inputs into the soil. However, the focus of these studies has been on the relationship between aggregate stability and soil organic matter dynamics. How the effects of organic matter inputs on aggregate stability translate into soil erodibility under rainfall impacts has received much less attention. In this study, we performed field plot experiments to examine how organic matter inputs affect aggregate breakdown and surface sediment transport under field conditions in artificial rainfall events. Three pairs of plots were prepared by adding a mixture of grass and wheat straw to one of plots in each pair but not to the other, while all plots were treated in the same way otherwise. The rainfall events were applied some weeks later so that the applied organic residues had sufficient time for decomposition and incorporation into the soil. Surface runoff rate and sediment concentration showed substantial differences between the treatments with and without organic matter inputs. The plots with organic inputs had coarser and more stable aggregates and a rougher surface than the control plots without organic inputs, resulting in a higher infiltration rate and lower transport capacity of the surface runoff. Consequently, sediments exported from the amended plots were less concentrated but more enriched in suspended particles (<20 µm) than from the un-amended plots, indicating a more size-selective sediment transport. In contrast to the amended plots, there was an increase in the coarse particle fraction (> 250 µm) in the runoff from the plots with no organic matter inputs towards the

Regulation of aggregate size and pattern by adenosine and caffeine in cellular slime molds

PubMed Central

2012-01-01

Background Multicellularity in cellular slime molds is achieved by aggregation of several hundreds to thousands of cells. In the model slime mold Dictyostelium discoideum, adenosine is known to increase the aggregate size and its antagonist caffeine reduces the aggregate size. However, it is not clear if the actions of adenosine and caffeine are evolutionarily conserved among other slime molds known to use structurally unrelated chemoattractants. We have examined how the known factors affecting aggregate size are modulated by adenosine and caffeine. Result Adenosine and caffeine induced the formation of large and small aggregates respectively, in evolutionarily distinct slime molds known to use diverse chemoattractants for their aggregation. Due to its genetic tractability, we chose D. discoideum to further investigate the factors affecting aggregate size. The changes in aggregate size are caused by the effect of the compounds on several parameters such as cell number and size, cell-cell adhesion, cAMP signal relay and cell counting mechanisms. While some of the effects of these two compounds are opposite to each other, interestingly, both compounds increase the intracellular glucose level and strengthen cell-cell adhesion. These compounds also inhibit the synthesis of cAMP phosphodiesterase (PdsA), weakening the relay of extracellular cAMP signal. Adenosine as well as caffeine rescue mutants impaired in stream formation (pde4- and pdiA-) and colony size (smlA- and ctnA-) and restore their parental aggregate size. Conclusion Adenosine increased the cell division timings thereby making large number of cells available for aggregation and also it marginally increased the cell size contributing to large aggregate size. Reduced cell division rates and decreased cell size in the presence of caffeine makes the aggregates smaller than controls. Both the compounds altered the speed of the chemotactic amoebae causing a variation in aggregate size. Our data strongly suggests

Regulation of aggregate size and pattern by adenosine and caffeine in cellular slime molds.

PubMed

Jaiswal, Pundrik; Soldati, Thierry; Thewes, Sascha; Baskar, Ramamurthy

2012-01-23

Multicellularity in cellular slime molds is achieved by aggregation of several hundreds to thousands of cells. In the model slime mold Dictyostelium discoideum, adenosine is known to increase the aggregate size and its antagonist caffeine reduces the aggregate size. However, it is not clear if the actions of adenosine and caffeine are evolutionarily conserved among other slime molds known to use structurally unrelated chemoattractants. We have examined how the known factors affecting aggregate size are modulated by adenosine and caffeine. Adenosine and caffeine induced the formation of large and small aggregates respectively, in evolutionarily distinct slime molds known to use diverse chemoattractants for their aggregation. Due to its genetic tractability, we chose D. discoideum to further investigate the factors affecting aggregate size. The changes in aggregate size are caused by the effect of the compounds on several parameters such as cell number and size, cell-cell adhesion, cAMP signal relay and cell counting mechanisms. While some of the effects of these two compounds are opposite to each other, interestingly, both compounds increase the intracellular glucose level and strengthen cell-cell adhesion. These compounds also inhibit the synthesis of cAMP phosphodiesterase (PdsA), weakening the relay of extracellular cAMP signal. Adenosine as well as caffeine rescue mutants impaired in stream formation (pde4- and pdiA-) and colony size (smlA- and ctnA-) and restore their parental aggregate size. Adenosine increased the cell division timings thereby making large number of cells available for aggregation and also it marginally increased the cell size contributing to large aggregate size. Reduced cell division rates and decreased cell size in the presence of caffeine makes the aggregates smaller than controls. Both the compounds altered the speed of the chemotactic amoebae causing a variation in aggregate size. Our data strongly suggests that cytosolic glucose and

Controlled Dual Growth Factor Delivery From Microparticles Incorporated Within Human Bone Marrow-Derived Mesenchymal Stem Cell Aggregates for Enhanced Bone Tissue Engineering via Endochondral Ossification.

PubMed

Dang, Phuong N; Dwivedi, Neha; Phillips, Lauren M; Yu, Xiaohua; Herberg, Samuel; Bowerman, Caitlin; Solorio, Loran D; Murphy, William L; Alsberg, Eben

2016-02-01

Bone tissue engineering via endochondral ossification has been explored by chondrogenically priming cells using soluble mediators for at least 3 weeks to produce a hypertrophic cartilage template. Although recapitulation of endochondral ossification has been achieved, long-term in vitro culture is required for priming cells through repeated supplementation of inductive factors in the media. To address this challenge, a microparticle-based growth factor delivery system was engineered to drive endochondral ossification within human bone marrow-derived mesenchymal stem cell (hMSC) aggregates. Sequential exogenous presentation of soluble transforming growth factor-β1 (TGF-β1) and bone morphogenetic protein-2 (BMP-2) at various defined time courses resulted in varying degrees of chondrogenesis and osteogenesis as demonstrated by glycosaminoglycan and calcium content. The time course that best induced endochondral ossification was used to guide the development of the microparticle-based controlled delivery system for TGF-β1 and BMP-2. Gelatin microparticles capable of relatively rapid release of TGF-β1 and mineral-coated hydroxyapatite microparticles permitting more sustained release of BMP-2 were then incorporated within hMSC aggregates and cultured for 5 weeks following the predetermined time course for sequential presentation of bioactive signals. Compared with cell-only aggregates treated with exogenous growth factors, aggregates with incorporated TGF-β1- and BMP-2-loaded microparticles exhibited enhanced chondrogenesis and alkaline phosphatase activity at week 2 and a greater degree of mineralization by week 5. Staining for types I and II collagen, osteopontin, and osteocalcin revealed the presence of cartilage and bone. This microparticle-incorporated system has potential as a readily implantable therapy for healing bone defects without the need for long-term in vitro chondrogenic priming. Significance: This study demonstrates the regulation of chondrogenesis

The effect of desmopressin on platelet aggregation defect in systemic amyloidosis: a preliminary report.

PubMed

Demiroğlu, H; Barişta, I; Gürsoy, M; Oymak, O; Dündar, S

1996-05-01

Systemic amyloidosis may often be complicated with haemorrhagic tendency. The causes of this manifestation are factor deficiencies, hyperfibrinolysis and vasculopathy. In order to investigate the role of platelets, if any, we performed platelet aggregation tests with different aggregants in 10 patients with systemic amyloidosis due to familial Mediterranean fever and 10 healthy controls. Platelet aggregation was defective with different aggregants (ADP, epinephrine, collagen) in patients compared with controls. Platelet aggregation tests repeated after desmopressin (DDAVP) administration were normalized. These findings may suggest a role of a platelet aggregation defect in haemorrhagic diathesis complicating systemic amyloidosis. DDAVP may benefit patients with this disease in case of bleeding and before surgical interventions.

Activated stress response pathways within multicellular aggregates utilize an autocrine component.

PubMed

Jack, Graham D; Cabrera, M Carla; Manning, Michael L; Slaughter, Stephen M; Potts, Malcolm; Helm, Richard F

2007-04-01

Multicellular aggregates (spheroids) of primary human foreskin fibroblasts (HFF-2) and a glioblastoma cell line (T98G) entered and exited from long term (2 weeks) metabolic arrest utilizing an autocrine response. Cytokine production (specifically IFN-gamma) activated a Gadd45alpha/p38 pathway that led to increased AP-1 (c-jun and ATF3) transcription factor levels, augmenting cytokine production in an autocrine fashion. Whereas HFF-2 aggregates were capable of surviving long term arrest and recovery during NF-kappaB inhibition independent of JNK activation, T98G aggregates were not. Such endogenous processes are not easily observed with adherent monolayer cell culturing systems, strongly suggesting that more emphasis needs to be placed on determining the operational signal transduction cascades within multicellular aggregates. Extracellular inputs such as spheroid formation, arrest, and regrowth as monolayers invoke intracellular signaling responses converging at the AP-1 transcription factor level. Variations in responses are both cell type and transformation state dependent and require an autocrine cytokine component. The data are discussed in relation to the wounding response and avascular tumor growth mechanisms.

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

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

Milton Wu; Paul Yuran

2006-12-31

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

Transfer factors of natural radionuclides and (137)Cs from soil to plants used in traditional medicine in central Serbia.

PubMed

Djelic, Gorica; Krstic, Dragana; Stajic, Jelena M; Milenkovic, Biljana; Topuzovic, Marina; Nikezic, Dragoslav; Vucic, Dusica; Zeremski, Tijana; Stankovic, Milan; Kostic, Dragana

2016-07-01

Transfer factors of natural radionuclides and (137)Cs from soil to plants used in traditional medicine were determined. The transfer factors (TF) were calculated as Bq kg(-1) of dry plant per Bq kg(-1) of dry soil. Mass activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in soil and plant samples were measured with high purity germanium detector (HPGe). The concentrations of As, Co, Cr, Cu, Mn, Ni, Pb and Zn were determined, as well as the cation exchange capacity (CEC) and the content of exchangeable cations (Ca, Mg, K, Na). Wide ranges of values were obtained for all the metals, especially for Cr and Ni. The Absalom model was used for determination of the amount of (137)Cs transferred from soil to plant based on soil characteristics such as pH, exchangeable potassium, humus and clay contents. The estimated transfer factors were in the range from 0.011 to 0.307 with an arithmetic mean of 0.071, median of 0.050, geometric mean of 0.053 and geometric standard deviation (GSD) of 2.08. This value agreed well with that calculated from the measurements of 0.069, geometric mean 0.040 and GSD 3.19. Correlations between radionuclides, metals, physicochemical properties and transfer factors were determined by Spearman correlation coefficient. There was a strong positive correlation between (137)Cs transfer factor and the ratio of transfer factor for K and (137)Cs. Principal Component Analysis (PCA) was performed in order to identify some pattern of data. Copyright © 2016. Published by Elsevier Ltd.

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

PubMed Central

Tyedmers, Jens

2012-01-01

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

Förster Resonance Energy Transfer Evidence for Lysozyme Oligomerization in Lipid Environment

PubMed Central

Trusova, Valeriya M.; Gorbenko, Galyna P.; Sarkar, Pabak; Luchowski, Rafal; Akopova, Irina; Patsenker, Leonid D.; Klochko, Oleksii; Tatarets, Anatoliy L.; Kudriavtseva, Yuliia O.; Terpetschnig, Ewald A.; Gryczynski, Ignacy; Gryczynski, Zygmunt

2012-01-01

Intermolecular time-resolved and single-molecule Förster resonance energy transfer (FRET) have been applied to detect quantitatively the aggregation of polycationic protein lysozyme (Lz) in the presence of lipid vesicles composed of phosphatidylcholine (PC) and its mixture with 5, 10, 20, or 40 mol % of phosphatidylglycerol (PG) (PG5, PG10, PG20, or PG40, respectively). Upon binding to PC, PG5, or PG10 model membranes, Lz was found to retain its native monomeric conformation, while increasing content of anionic lipid up to 20 or 40 mol % resulted in the formation of Lz aggregates. The structural parameters of protein self-association (the degree of oligomerization, the distance between the monomers in protein assembly, and the fraction of donors present in oligomers) have been derived. The crucial role of the factors such as lateral density of the adsorbed protein and electrostatic and hydrophobic Lz–lipid interactions in controlling the protein self-association behavior has been proposed. PMID:21126034

Non-Arrhenius protein aggregation.

PubMed

Wang, Wei; Roberts, Christopher J

2013-07-01

Protein aggregation presents one of the key challenges in the development of protein biotherapeutics. It affects not only product quality but also potentially impacts safety, as protein aggregates have been shown to be linked with cytotoxicity and patient immunogenicity. Therefore, investigations of protein aggregation remain a major focus in pharmaceutical companies and academic institutions. Due to the complexity of the aggregation process and temperature-dependent conformational stability, temperature-induced protein aggregation is often non-Arrhenius over even relatively small temperature windows relevant for product development, and this makes low-temperature extrapolation difficult based simply on accelerated stability studies at high temperatures. This review discusses the non-Arrhenius nature of the temperature dependence of protein aggregation, explores possible causes, and considers inherent hurdles for accurately extrapolating aggregation rates from conventional industrial approaches for selecting accelerated conditions and from conventional or more advanced methods of analyzing the resulting rate data.

Morphology-Variable Aggregates Prepared from Cholesterol-Containing Amphiphilic Glycopolymers: Their Protein Recognition/Adsorption and Drug Delivery Applications

PubMed Central

Wang, Zhao; Luo, Ting; Cao, Amin; Sun, Jingjing; Jia, Lin

2018-01-01

In this study, a series of diblock glycopolymers, poly(6-O-methacryloyl-d-galactopyranose)-b-poly(6-cholesteryloxyhexyl methacrylate) (PMAgala-b-PMAChols), with cholesterol/galactose grafts were prepared through a sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and deprotection process. The glycopolymers could self-assemble into aggregates with various morphologies depending on cholesterol/galactose-containing block weight ratios, as determined by transmission electronic microscopy (TEM) and dynamic laser light scattering (DLS). In addition, the lectin (Ricinus communis agglutinin II, RCA120) recognition and bovine serum albumin (BSA) adsorption of the PMAgala-b-PMAChol aggregates were evaluated. The SK-Hep-1 tumor cell inhibition properties of the PMAgala-b-PMAChol/doxorubicin (DOX) complex aggregates were further examined in vitro. Results indicate that the PMAgala-b-PMAChol aggregates with various morphologies showed different interaction/recognition features with RCA120 and BSA. Spherical aggregates (d ≈ 92 nm) possessed the highest RCA120 recognition ability and lowest BSA protein adsorption. In addition, the DOX-loaded spherical complex aggregates exhibited a better tumor cell inhibition property than those of nanofibrous complex aggregates. The morphology-variable aggregates derived from the amphiphilic glycopolymers may serve as multifunctional biomaterials with biomolecular recognition and drug delivery features. PMID:29495614

Effects of garlic extract on platelet aggregation: a randomized placebo-controlled double-blind study.

PubMed

Morris, J; Burke, V; Mori, T A; Vandongen, R; Beilin, L J

1995-01-01

1. Studies of the effects of garlic on platelet aggregation have produced inconsistent results possibly related to variations in study design and in the garlic preparations used. 2. The present study examined the effects on platelet aggregation and serum thromboxane and lyso-platelet activating factor, of feeding garlic extract to healthy men using a placebo-controlled, double-blind design. The effects of the same garlic preparation on platelet aggregation in vitro were also investigated. 3. There were no significant differences in platelet aggregation with adenosine diphosphate, platelet activating factor (PAF) or collagen according to treatment group. Serum thromboxane and lysoPAF also showed no change related to garlic supplements. 4. In vitro aggregation with collagen decreased linearly with increasing amounts of garlic extract, but concentrations were higher than those attainable in vivo. Gastrointestinal side effects prevented the use of higher doses of garlic which must be considered to be pharmacological as they exceed changes achievable by dietary modification.

GRAY: a program to calculate gray-body radiation heat-transfer view factors from black-body view factors

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

Wong, R. L.

1976-06-14

Program GRAY is written to perform the matrix manipulations necessary to convert black-body radiation heat-transfer view factors to gray-body view factors as required by thermal analyzer codes. The black-body view factors contain only geometric relationships. Program GRAY allows the effects of multiple gray-body reflections to be included. The resulting effective gray-body factors can then be used with the corresponding fourth-power temperature differences to obtain the net radiative heat flux. The program is written to accept a matrix input or the card image output generated by the black-body view factor program CNVUFAC. The resulting card image output generated by GRAY ismore » in a form usable by the TRUMP thermal analyzer.« less

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

NASA Astrophysics Data System (ADS)

Wasilewska, Marta; Gardziejczyk, Wladysław; Gierasimiuk, Pawel

2018-05-01

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

Graphene quantum dots for the inhibition of β amyloid aggregation

NASA Astrophysics Data System (ADS)

Liu, Yibiao; Xu, Li-Ping; Dai, Wenhao; Dong, Haifeng; Wen, Yongqiang; Zhang, Xueji

2015-11-01

The aggregation of Aβ peptides is a crucial factor leading to Alzheimer's disease (AD). Inhibiting the Aβ peptide aggregation has become one of the most essential strategies to treat AD. In this work, efficient and low-cytotoxicity inhibitors, graphene quantum dots (GQDs) are reported for their application in inhibiting the aggregation of Aβ peptides. Compared to other carbon materials, the low cytotoxicity and great biocompatibility of GQDs give an advantage to the clinical research for AD. In addition, the GQDs may cross the blood-brain barrier (BBB) because of the small size. It is believed that GQDs may be therapeutic agents against AD. This work provides a novel insight into the development of Alzheimer's drugs.The aggregation of Aβ peptides is a crucial factor leading to Alzheimer's disease (AD). Inhibiting the Aβ peptide aggregation has become one of the most essential strategies to treat AD. In this work, efficient and low-cytotoxicity inhibitors, graphene quantum dots (GQDs) are reported for their application in inhibiting the aggregation of Aβ peptides. Compared to other carbon materials, the low cytotoxicity and great biocompatibility of GQDs give an advantage to the clinical research for AD. In addition, the GQDs may cross the blood-brain barrier (BBB) because of the small size. It is believed that GQDs may be therapeutic agents against AD. This work provides a novel insight into the development of Alzheimer's drugs. Electronic supplementary information (ESI) available: Dose-dependent inhibition of Aβ1-42 fibrillization by GQDs; the photoluminescence spectra of all five GQDs with different charges in water/ethanol; TEM images of other four GQDs with different charges. See DOI: 10.1039/c5nr06282a

Evaluation of Canadian unconfined aggregate freeze-thaw tests for identifying nondurable aggregates.

DOT National Transportation Integrated Search

2012-06-01

Concrete is the most widely used material in construction. Aggregates contribute 60% to 75% of the total volume : of concrete. The aggregates play a key role in concrete durability. The U.S. Midwest has many aggregates that can : show distress in the...

Crushed aggregates for roads and their properties for frost protection

NASA Astrophysics Data System (ADS)

Kuznetsova, Elena; Willy Danielsen, Svein

2015-04-01

of the road system. According to new specification; the size of large stones for this layer should be maximum 0.5 m (longest edge) or ½ layer thickness. And minimum 30% of stones should be less than 90 mm. Fines content (<0.063 mm) should be maximum 15% of the material less than 22.4 mm. Analysing these new requirements, several questions are arising. First of all how this materials size will affect heat exchange in the layer, secondly - if the allowable fines content will make the materials frost susceptible. For calculations of frost protection layer thickness the knowledge of thermal conductivity of the aggregate layers is required. Handbook for geotechnical investigations of the soils provides this data for natural gravel which is limited by 0.7 - 1.3 W/mK. But when it comes to the crushed rocks, it can be significantly increased due to the higher conductivity of minerals (especially if they contain high amount of quartz), as well as due to higher effective conductivity. In rock-fill materials, i.e. materials with large particles and low degree of saturation, convection and radiation are the predominant heat transfer mechanisms. Convection and radiation can increase the effective conductivity by factor 2-10. Lebeau and Konrad (2007) showed that convection heat transfer could lead to the formation of undesirable permafrost conditions in toe drains of embankment dams located in Northern Quebec, i.e. in areas where there are no naturally occurring permafrost soils. In a frost design method the required parameter values of crushed rock aggregates are thermal conductivity, density and water content. The heat transfer during the freezing of natural soils is assumed proportional to thermal conductivity of the material. In a coarse-grained material with abundant pore space, convective heat transfer and radiation may be a considerable factor, sometimes even more significant than conduction. Specifications used by pavement engineers in most countries are solely based on

Pheromone-Regulated Expression of Sex Pheromone Plasmid pAD1-Encoded Aggregation Substance Depends on at Least Six Upstream Genes and a cis-Acting, Orientation-Dependent Factor

PubMed Central

Muscholl-Silberhorn, Albrecht B.

2000-01-01

Conjugative transfer of Enterococcus faecalis-specific sex pheromone plasmids relies on an adhesin, called aggregation substance, to confer a tight cell-to-cell contact between the mating partners. To analyze the dependence of pAD1-encoded aggregation substance, Asa1, on pheromone induction, a variety of upstream fragments were fused to an α-amylase reporter gene, amyL, by use of a novel promoter probe vector, pAMY-em1. For pheromone-regulated α-amylase activity, a total of at least six genes, traB, traC, traA, traE1, orfY, and orf1, are required: TraB efficiently represses asa1 (by a mechanism unrelated to its presumptive function in pheromone shutdown, since a complete shutdown is observed exclusively in the presence of traC); only traC can relieve traB-mediated repression in a pheromone-dependent manner. In addition to traB, traA is required but not sufficient for negative control. Mutational inactivation of traE1, orfY, or orf1, respectively, results in a total loss of α-amylase activity for constructs normally mediating constitutive expression. Inversion of a fragment covering traA, P0, and traE1 without disrupting any gene or control element switches off amyL or asa1 expression, indicating the involvement of a cis-acting, orientation-dependent factor (as had been shown for plasmid pCF10). Unexpectedly, pAD1 represses all pAMY-em1 derivatives in trans, while its own pheromone-dependent functions are unaffected. The discrepancy between the new data and those of former studies defining TraE1 as a trans-acting positive regulator is discussed. PMID:10850999

Factors Affecting the Transfer of Basic Combat Skills Training in the Air Force

DTIC Science & Technology

2006-03-01

Kaiser - Meyer - Olkin Measure of Sampling Adequacy (KMO) and Bartlett’s test of Sphericity. The items reported a KMO=.87 and χ2 = 5,158.57, p < .01...Results Factor Analysis Table E1 Kaiser - Meyer - Olkin (KMO) and Bartlett’s Test of Sphericity for Perceived Training Transfer and Transfer Enhancing...Activities KMO Χ2 df Sig. Kaiser - Meyer - Olkin Measure of Sampling Adequacy .87 Bartletts Test of Sphericity 5,158.57 66 .000 100

Structural Change of Aerosol Particle Aggregates with Exposure to Elevated Relative Humidity.

PubMed

Montgomery, James F; Rogak, Steven N; Green, Sheldon I; You, Yuan; Bertram, Allan K

2015-10-20

Structural changes of aggregates composed of inorganic salts exposed to relative humidity (RH) between 0 and 80% after formation at selected RH between 0 and 60% were investigated using a tandem differential mobility analyzer (TDMA) and fluorescence microscopy. The TDMA was used to measure a shift in peak mobility diameter for 100-700 nm aggregates of hygroscopic aerosol particles composed of NaCl, Na2SO4, (NH4)2SO4, and nonhygroscopic Al2O3 as the RH was increased. Aggregates of hygroscopic particles were found to shrink when exposed to RH greater than that during the aggregation process. The degree of aggregate restructuring is greater for larger aggregates and greater increases in RH. Growth factors (GF) calculated from mobility diameter measurements as low as 0.77 were seen for NaCl before deliquescence. The GF subsequently increased to 1.23 at 80% RH, indicating growth after deliquescence. Exposure to RH lower than that experienced during aggregation did not result in structural changes. Fluorescent microscopy confirmed that aggregates formed on wire surfaces undergo an irreversible change in structure when exposed to elevated RH. Analysis of 2D movement of aggregates shows a displacement of 5-13% compared to projected length of initial aggregate from a wire surface. Surface tension due to water adsorption within the aggregate structure is a potential cause of the structural changes.

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

USGS Publications Warehouse

Wilburn, David R.; Goonan, Thomas G.

1998-01-01

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

[Platelet function in acute myeloid leukemia. II. Aggregation of isolated platelets].

PubMed

Zawilska, K; Komarnicki, M; Mańka, B

1978-01-01

In 22 patients with acute myeloid leukaemia (17 cases of myeloblastic leukaemia, 4 cases of myelomonocytic leukaemia and 1 case of undifferentiated-cell leukaemia) platelets were isolated from the plasma by the method of Nicholls and Hampton as modified by Levy-Toledano by centrifugation in albumin gradient. The aim of platelet isolation was their "concentration" in cases of thrombocytopenia to values making possible aggregation tests, and platelet separation from the influence of plasma factors. Then aggregation of isolated platelets caused by ADP was studied. In 16 out of 22 patients a fall of aggregation was observed, with the mean values of aggregation rate and intensity were significantly lower. Parallelly done determinations of aggregating activity released from the platelets by thrombin showed lower values as compared with platelets from healthy subjects. In might be thought, in this connection, that the demonstrated reduction of isolated platelets is associated with a diminution of the nucleotide pool or disturbances of the platelet release reaction. The disturbances of the platelet release reaction. The disturbances of aggregation of isolated platelets and reduction of the aggregating activity were most pronounced in acute myelomonocytic leukaemia.

Strategic factors in the development of the National Technology Transfer Network

NASA Technical Reports Server (NTRS)

Root, Jonathan F.; Stone, Barbara A.

1993-01-01

Broad consensus among industry and government leaders has developed over the last decade on the importance of applying the U.S. leadership in research and development (R&D) to strengthen competitiveness in the global marketplace, and thus enhance national prosperity. This consensus has emerged against the backdrop of increasing economic competition, and the dramatic reduction of military threats to national security with the end of the Cold War. This paper reviews the key factors and considerations that shaped - and continue to influence - the development of the Regional Technoloty Transfer Centers (RTTC) and the National Technology Transfer Center (NTTC). Also, the future role of the national network in support of emerging technology policy initiatives will be explored.

Impact of Cavitation, High Shear Stress and Air/Liquid Interfaces on Protein Aggregation.

PubMed

Duerkop, Mark; Berger, Eva; Dürauer, Astrid; Jungbauer, Alois

2018-03-25

The reported impact of shear stress on protein aggregation has been contradictory. At high shear rates, the occurrence of cavitation or entrapment of air is reasonable and their effects possibly misattributed to shear stress. Nine different proteins (α-lactalbumin, two antibodies, fibroblast growth factor 2, granulocyte colony stimulating factor [GCSF], green fluorescence protein [GFP], hemoglobin, human serum albumin, and lysozyme) are tested for their aggregation behavior on vapor/liquid interfaces generated by cavitation and compared it to the isolated effects of high shear stress and air/liquid interfaces generated by foaming. Cavitation induced the aggregation of GCSF by +68.9%, hemoglobin +4%, and human serum albumin +2.9%, compared to a control, whereas the other proteins do not aggregate. The protein aggregation behaviors of the different proteins at air/liquid interfaces are similar to cavitation, but the effect is more pronounced. Air-liquid interface induced the aggregation of GCSF by +94.5%, hemoglobin +35.5%, and human serum albumin (HSA) +31.1%. The results indicate that the sensitivity of a certain protein toward cavitation is very similar to air/liquid-induced aggregation. Hence, hydroxyl radicals cannot be seen as the driving force for protein aggregation when cavitation occurs. Further, high shear rates of up to 10 8  s -1 do not affect any of the tested proteins. Therefore, also within this study generated extremely high isolated shear rates cannot be considered to harm structural integrity when processing proteins. © 2018 The Authors. Biotechnology Journal Published by Wiley-VCH Verlag GmbH & Co. KGaA.

The Aggregate Representation of Terrestrial Land Covers Within Global Climate Models (GCM)

NASA Technical Reports Server (NTRS)

Shuttleworth, W. James; Sorooshian, Soroosh

1996-01-01

This project had four initial objectives: (1) to create a realistic coupled surface-atmosphere model to investigate the aggregate description of heterogeneous surfaces; (2) to develop a simple heuristic model of surface-atmosphere interactions; (3) using the above models, to test aggregation rules for a variety of realistic cover and meteorological conditions; and (4) to reconcile biosphere-atmosphere transfer scheme (BATS) land covers with those that can be recognized from space; Our progress in meeting these objectives can be summarized as follows. Objective 1: The first objective was achieved in the first year of the project by coupling the Biosphere-Atmosphere Transfer Scheme (BATS) with a proven two-dimensional model of the atmospheric boundary layer. The resulting model, BATS-ABL, is described in detail in a Masters thesis and reported in a paper in the Journal of Hydrology Objective 2: The potential value of the heuristic model was re-evaluated early in the project and a decision was made to focus subsequent research around modeling studies with the BATS-ABL model. The value of using such coupled surface-atmosphere models in this research area was further confirmed by the success of the Tucson Aggregation Workshop. Objective 3: There was excellent progress in using the BATS-ABL model to test aggregation rules for a variety of realistic covers. The foci of attention have been the site of the First International Satellite Land Surface Climatology Project Field Experiment (FIFE) in Kansas and one of the study sites of the Anglo-Brazilian Amazonian Climate Observational Study (ABRACOS) near the city of Manaus, Amazonas, Brazil. These two sites were selected because of the ready availability of relevant field data to validate and initiate the BATS-ABL model. The results of these tests are given in a Masters thesis, and reported in two papers. Objective 4: Progress far exceeded original expectations not only in reconciling BATS land covers with those that can be

Anti-protein aggregation is a potential target for preventing delayed neuronal death after transient ischemia.

PubMed

Ge, Pengfei; Luo, Yinan; Wang, Haifeng; Ling, Feng

2009-12-01

Brain ischemia has been an important risk factor for human being health, there is no effective medicine can be used to protect delayed neuronal injury or death secondary to blood reperfusion following ischemia. Recent discovery shows protein aggregation is an important factor resulting in ischemia-induced neuron death. Therefore, we propose the hypothesis that inhibiting protein aggregation may be an effective way to prevent delayed neuronal death after transient ischemia. At present, in vitro studies show some chemicals such as 4PBA (sodium 4-phenylbutyrate) and trehalose have the features of antagonizing protein aggregation in vitro. Moreover, polyQ-binding peptide (QBP1), geldanamycin, amino acids and amino acid derivatives have been also used in vitro to decrease aggregation and to increase protein stability. Although in vivo and systematical study should be performed to evaluate their effects of anti-protein aggregation, this enlightening us on using them to protect ischemic-induced neuronal death, and find new potential chemicals or methods which could be effective in keeping protein stable and prevent forming aggregates.

Conformational analysis of misfolded protein aggregation by FRET and live-cell imaging techniques.

PubMed

Kitamura, Akira; Nagata, Kazuhiro; Kinjo, Masataka

2015-03-16

Cellular homeostasis is maintained by several types of protein machinery, including molecular chaperones and proteolysis systems. Dysregulation of the proteome disrupts homeostasis in cells, tissues, and the organism as a whole, and has been hypothesized to cause neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and Huntington's disease (HD). A hallmark of neurodegenerative disorders is formation of ubiquitin-positive inclusion bodies in neurons, suggesting that the aggregation process of misfolded proteins changes during disease progression. Hence, high-throughput determination of soluble oligomers during the aggregation process, as well as the conformation of sequestered proteins in inclusion bodies, is essential for elucidation of physiological regulation mechanism and drug discovery in this field. To elucidate the interaction, accumulation, and conformation of aggregation-prone proteins, in situ spectroscopic imaging techniques, such as Förster/fluorescence resonance energy transfer (FRET), fluorescence correlation spectroscopy (FCS), and bimolecular fluorescence complementation (BiFC) have been employed. Here, we summarize recent reports in which these techniques were applied to the analysis of aggregation-prone proteins (in particular their dimerization, interactions, and conformational changes), and describe several fluorescent indicators used for real-time observation of physiological states related to proteostasis.

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

Electronic coupling in long-range electron transfer

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

Newton, M.D.

1996-12-31

One of the quantities crucial in controlling electron transfer (et) kinetics is the donor/acceptor electronic coupling integral (HDA). Recent theoretical models for HDA will be presented, and the results of ab initio computational implementation will be reported and analyzed for several metal-to-metal ligand charge transfer processes in complex molecular aggregates. New procedures for defining diabatic states, including a generalization of the Mulliken-Hush model, allow applications to optical and excited state as well as ground state et in a many-state framework.

Fireproof impact limiter aggregate packaging inside shipping containers

DOEpatents

Byington, Gerald A.; Oakes, Jr., Raymon Edgar; Feldman, Matthew Rookes

2001-01-01

The invention is a product and a process for making a fireproof, impact limiter, homogeneous aggregate material for casting inside a hazardous material shipping container, or a double-contained Type-B nuclear shipping container. The homogeneous aggregate material is prepared by mixing inorganic compounds with water, pouring the mixture into the void spaces between an inner storage containment vessel and an outer shipping container, vibrating the mixture inside the shipping container, with subsequent curing, baking, and cooling of the mixture to form a solidified material which encapsulates an inner storage containment vessel inside an outer shipping container. The solidified material forms a protective enclosure around an inner storage containment vessel which may store hazardous, toxic, or radioactive material. The solidified material forms a homogeneous fire-resistant material that does not readily transfer heat, and provides general shock and specific point-impact protection, providing protection to the interior storage containment vessel. The material is low cost, may contain neutron absorbing compounds, and is easily formed into a variety of shapes to fill the interior void spaces of shipping containers.

Aggregation-induced chemical reactions: acid dissociation in growing water clusters.

PubMed

Forbert, Harald; Masia, Marco; Kaczmarek-Kedziera, Anna; Nair, Nisanth N; Marx, Dominik

2011-03-23

Understanding chemical reactivity at ultracold conditions, thus enabling molecular syntheses via interstellar and atmospheric processes, is a key issue in cryochemistry. In particular, acid dissociation and proton transfer reactions are ubiquitous in aqueous microsolvation environments. Here, the full dissociation of a HCl molecule upon stepwise solvation by a small number of water molecules at low temperatures, as relevant to helium nanodroplet isolation (HENDI) spectroscopy, is analyzed in mechanistic detail. It is found that upon successive aggregation of HCl with H(2)O molecules, a series of cyclic heteromolecular structures, up to and including HCl(H(2)O)(3), are initially obtained before a precursor state for dissociation, HCl(H(2)O)(3)···H(2)O, is observed upon addition of a fourth water molecule. The latter partially aggregated structure can be viewed as an "activated species", which readily leads to dissociation of HCl and to the formation of a solvent-shared ion pair, H(3)O(+)(H(2)O)(3)Cl(-). Overall, the process is mostly downhill in potential energy, and, in addition, small remaining barriers are overcome by using kinetic energy released as a result of forming hydrogen bonds due to aggregation. The associated barrier is not ruled by thermal equilibrium but is generated by athermal non-equilibrium dynamics. These "aggregation-induced chemical reactions" are expected to be of broad relevance to chemistry at ultralow temperature much beyond HENDI spectroscopy.

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

PubMed

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

2016-01-20

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

Factors affecting the efficiency of embryo transfer in the domestic ferret (Mustela putorius furo).

PubMed

Li, Ziyi; Sun, Xingshen; Chen, Juan; Leno, Gregory H; Engelhardt, John F

2006-07-15

Embryo transfer (ET) to recipient females is a foundational strategy for a number of assisted reproductive technologies, including cloning by somatic cell nuclear transfer. In an attempt to develop efficient ET in domestic ferrets, factors affecting development of transferred embryo were investigated. Unilateral and bilateral transfer of zygotes or blastocysts in the oviduct or uterus was evaluated in recipient nulliparous or primiparous females. Developing fetuses were collected from recipient animals 21 days post-copulation and examined. The percentage of fetal formation was different (P<0.05) for unilateral and bilateral transfer of zygotes (71%) in nulliparous females with bilateral transfer (56%) in primiparous recipients. The percentage (90%) of fetal formation in nulliparous recipients following unilateral transfer of blastocysts was higher (P<0.05) than that observed in primiparous recipients with bilateral ET (73%). Notably, the percentage of fetal formation was higher (P<0.05) when blastocyts were transferred as compared to zygotes (90% versus 71%). Transuterine migration of embryos occurred following all unilateral transfers and also in approximately 50% of bilateral transfers with different number of embryos in each uterine horn. These data will help to facilitate the development of assisted reproductive strategies in the ferret and could lead to the use of this species for modeling human disease and for conservation of the endangered Mustelidae species such as black-footed ferret and European mink.

Factors affecting the efficiency of embryo transfer in the domestic ferret (Mustela putorius furo)

PubMed Central

Li, Ziyi; Sun, Xingshen; Chen, Juan; Leno, Gregory H.; Engelhardt, John F.

2007-01-01

Embryo transfer (ET) to recipient females is a foundational strategy for a number of assisted reproductive technologies, including cloning by somatic cell nuclear transfer. In an attempt to develop efficient ET in domestic ferrets, factors affecting development of transferred embryo were investigated. Unilateral and bilateral transfer of zygotes or blastocysts in the oviduct or uterus was evaluated in recipient nulliparous or primiparous females. Developing fetuses were collected from recipient animals 21 days post-copulation and examined. The percentage of fetal formation was different (P < 0.05) for unilateral and bilateral transfer of zygotes (71%) in nulliparous females with bilateral transfer (56%) in primiparous recipients. The percentage (90%) of fetal formation in nulliparous recipients following unilateral transfer of blastocysts was higher (P < 0.05) than that observed in primiparous recipients with bilateral ET (73%). Notably, the percentage of fetal formation was higher (P < 0.05) when blastocyts were transferred as compared to zygotes (90% versus 71%). Transuterine migration of embryos occurred following all unilateral transfers and also in approximately 50% of bilateral transfers with different number of embryos in each uterine horn. These data will help to facilitate the development of assisted reproductive strategies in the ferret and could lead to the use of this species for modeling human disease and for conservation of the endangered Mustelidae species such as black-footed ferret and European mink. PMID:16330092

The chaperonin CCT promotes the formation of fibrillar aggregates of γ-tubulin.

PubMed

Pouchucq, Luis; Lobos-Ruiz, Pablo; Araya, Gissela; Valpuesta, José María; Monasterio, Octavio

2018-04-01

The type II chaperonin CCT is involved in the prevention of the pathogenesis of numerous human misfolding disorders, as it sequesters misfolded proteins, blocks their aggregation and helps them to achieve their native state. In addition, it has been reported that CCT can prevent the toxicity of non-client amyloidogenic proteins by the induction of non-toxic aggregates, leading to new insight in chaperonin function as an aggregate remodeling factor. Here we add experimental evidence to this alternative mechanism by which CCT actively promotes the formation of conformationally different aggregates of γ-tubulin, a non-amyloidogenic CCT client protein, which are mediated by specific CCT-γ-tubulin interactions. The in vitro-induced aggregates were in some cases long fiber polymers, which compete with the amorphous aggregates. Direct injection of unfolded purified γ-tubulin into single-cell zebra fish embryos allowed us to relate this in vitro activity with the in vivo formation of intracellular aggregates. Injection of a CCT-binding deficient γ-tubulin mutant dramatically diminished the size of the intracellular aggregates, increasing the toxicity of the misfolded protein. These results point to CCT having a role in the remodeling of aggregates, constituting one of its many functions in cellular proteostasis. Copyright © 2018. Published by Elsevier B.V.

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

NASA Astrophysics Data System (ADS)

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

2015-09-01

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

Retention of ferrofluid aggregates at the target site during magnetic drug targeting

NASA Astrophysics Data System (ADS)

Asfer, Mohammed; Saroj, Sunil Kumar; Panigrahi, Pradipta Kumar

2017-08-01

The present study reports the retention dynamics of a ferrofluid aggregate localized at the target site inside a glass capillary (500 × 500 μm2 square cross section) against a bulk flow of DI water (Re = 0.16 and 0.016) during the process of magnetic drug targeting (MDT). The dispersion dynamics of iron oxide nanoparticles (IONPs) into bulk flow for different initial size of aggregate at the target site is reported using the brightfield visualization technique. The flow field around the aggregate during the retention is evaluated using the μPIV technique. IONPs at the outer boundary experience a higher shear force as compared to the magnetic force, resulting in dispersion of IONPs into the bulk flow downstream to the aggregate. The blockage effect and the roughness of the outer boundary of the aggregate resulting from chain like clustering of IONPs contribute to the flow recirculation at the downstream region of the aggregate. The entrapment of seeding particles inside the chain like clusters of IONPs at the outer boundary of the aggregate reduces the degree of roughness resulting in a streamlined aggregate at the target site at later time. The effect of blockage, structure of the aggregate, and disturbed flow such as recirculation around the aggregate are the primary factors, which must be investigated for the effectiveness of the MDT process for in vivo applications.

Folding and Aggregation of Mucin Domains.

NASA Astrophysics Data System (ADS)

Urbanc, Brigita; Bansil, Rama; Turner, Bradley

2007-03-01

Mucin glycoproteins consist of tandem repeating glycosylated regions flanked by non-repetitive protein domains with little glycosylation. These non-repetitive domains are involved in polymerization of mucin via disulfide bonds and play an important role in the pH dependent gelation of gastric mucin, which is essential to protecting the stomach from autodigestion. We have examined the folding and aggregation of the non-repetitive sequence of von Willebrand factor vWF-C1 domain (67 amino acids) and PGM 2X (242 amino acids) using Discrete Molecular Dynamics (four-bead protein model with hydrogen bonding and amino acid-specific hydrophobic/hydrophilic and electrostatic interactions of side chains). Simulations of vWF C1 show 4-6 β-strands separated by turns/loops with more loops at lower pH. A simulation of several vWF C1 proteins at low pH shows aggregates still with a high content of β-strands and enhanced turn/loop regions. For the PGM 2X simulation the contact map shows several salt bridges enclosing hairpin turns. The implications of these simulations for describing the aggregation/gelation of PGM will be discussed.

Convective Aggregation, Climate Sensitivity, and the Importance of Radiation Physics in Weather and Climate

NASA Astrophysics Data System (ADS)

Emanuel, K.

2015-12-01

Since the revolutionary work of Vilhelm Bjerknes, Jule Charney, and Eric Eady, geophysical fluid dynamics has dominated weather research and continues to play an important in climate dynamics. Although the physics of radiative transfer is central to understanding climate, it has played a far smaller role in weather research and is given only rudimentary attention in most educational programs in meteorology. Yet key contemporary problems in atmospheric science, such as the Madden-Julian Oscillation and the self-aggregation of moist convection, do not appear to have been solved by approaches based strictly on fluid dynamics and moist adiabatic thermodynamics. Here I will argue that many outstanding problems in meteorology and climate science involve a nontrivial coupling of circulation and radiation physics. In particular, the phenomenon of self-aggregation of moist convection depends on the interaction of radiation with time-varying water vapor and clouds, with strong implications for such diverse problems as the Madden-Julian Oscillation, tropical cyclones, and the relative insensitivity of tropical climate to radiative forcing. This argues for an augmentation of radiative transfer physics in graduate curricula in atmospheric sciences.

Aggregate stability as an indicator of soil erodibility and soil physical quality: review and perspectives

NASA Astrophysics Data System (ADS)

Le Bissonnais, Yves; Chenu, Claire; Darboux, Frédéric; Duval, Odile; Legout, Cédric; Leguédois, Sophie; Gumiere, Silvio

2010-05-01

Aggregate breakdown due to water and rain action may cause surface crusting, slumping, a reduction of infiltration and interrill erosion. Aggregate stability determines the capacity of aggregates to resist the effects of water and rainfall. In this paper, we evaluated and reviewed the relevance of an aggregate stability measurement to characterize soil physical properties as well as to analyse the processes involved in these properties. Stability measurement assesses the sensitivity of soil aggregates to various basic disaggregation mechanisms such as slaking, differential swelling, dispersion and mechanical breakdown. It has been showed that aggregate size distributions of structural stability tests matched the size distributions of eroded aggregates under rainfall simulations and that erosion amount was well predicted using aggregate stability indexes. It means stability tests could be used to estimate both the erodibility and the size fractions that are available for crust formation and erosion processes. Several studies showed that organic matter was one of the main soil properties affecting soil stability. However, it has also been showed that aggregate stability of a given soil could vary within a year or between years. The factors controlling such changes have still to be specified. Aggregate stability appears therefore as a complex property, depending both on permanent soil characteristics and on dynamic factors such as the crusting stage, the climate and the biological activity. Despite, and may be, because of this complexity, aggregate stability seems an integrative and powerful indicator of soil physical quality. Future research efforts should look at the causes of short-term changes of structural stability, in order to fully understand all its aspects.

[Factors influencing relocation stress syndrome in patients following transfer from intensive care units].

PubMed

Park, Jin-Hee; Yoo, Moon-Sook; Son, Youn-Jung; Bae, Sun Hyoung

2010-06-01

The purpose of this study was to identify the levels of relocation stress syndrome (RSS) and influencing the stress experienced by Intensive Care Unit (ICU) patients just after transfer to general wards. A cross-sectional study was conducted with 257 patients who transferred from the intensive care unit. Data were collected through self-report questionnaires from May to October, 2009. Data were analyzed using the Pearson correlation coefficient, t-test, one-way ANOVA, and stepwise multiple linear regression with SPSS/WIN 12.0. The mean score for RSS was 17.80+/-9.16. The factors predicting relocation stress syndrome were symptom experience, differences in scope and quality of care provided by ICU and ward nursing staffs, satisfaction with transfer process, length of stay in ICU and economic status, and these factors explained 40% of relocation stress syndrome (F=31.61, p<.001). By understanding the stress experienced by ICU patients, nurses are better able to provide psychological support and thus more holistic care to critically ill patients. Further research is needed to consider the impact of relocation stress syndrome on patients' health outcomes in the recovery trajectory.

Technology Transfer Issues and a New Technology Transfer Model

ERIC Educational Resources Information Center

Choi, Hee Jun

2009-01-01

The following are major issues that should be considered for efficient and effective technology transfer: conceptions of technology, technological activity and transfer, communication channels, factors affecting transfer, and models of transfer. In particular, a well-developed model of technology transfer could be used as a framework for…

Precursor Ion–Ion Aggregation in the Brust–Schiffrin Synthesis of Alkanethiol Nanoparticles

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

Graham, Trent R.; Renslow, Ryan; Govind, Niranjan

Tetraoctylammonium bromide is used in the Brust-Schiffrin nanoparticle synthesis to phase-transfer chloroaurate ions from the aqueous phase to the organic phase. While it is established that the quaternary ammonium complex self-associates in the organic phase, the actual self-assembled structure is debated. We have confirmed the presence of ion-ion aggregates through quantitative 1H Nuclear Magnetic Resonance spectroscopy (NMR), pulsed field gradient, diffusion-ordered NMR (DOSY-NMR) and density functional theory (DFT) based NMR shift calculations. Tetraoctylammonium complexes (TOA-X, where X = Br, Cl, AuCl4-xBrx, AuBr4/Br and AuCl4-xBrx/Br) were investigated to measure the extraction of water into the organic phase. 1H NMR and DFTmore » based NMR shielding calculations indicated that deshielding of water is due to hydration of the anion and not the formation of the aqueous core of a reverse micelle. DOSYNMR results were consistent with the formation of small aggregates at typical Brust-Schiffrin synthesis concentrations. The extent of aggregation correlated with the size and electronegativity of the anion and was analyzed with a modified, isodesmic, indefinite aggregation model. The substitution of bromoauric acid for chlororoauric acid at conditions emulating the Brust-Schiffrin synthesis increased the aggregation of the quaternary ammonium complex. The increase in aggregation corresponded with an increase in the size of the produced nanoparticles from 4.3 to 4.6 nm. Understanding the selfassembly and supramolecular structure of precursors in the Brust-Schiffrin synthesis will enable further refinement of models that predict the growth of noble metal nanoparticles.« less

Measurement of the proton form factor ratio at low momentum transfer

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

Friedman, Moshe

Experiment E08-007-II measured the proton elastic form factor ratio μG E=G M in the momentum transfer range of Q 2 ~ 0.02 - 0.08 GeV 2, the lowest ever measured by polarization transfer techniques. The experiment was performed at the Thomas Jefferson National Accelerator Facility in Newport News, Virginia, USA during 2012. A polarized electron beam with energies of 1.1, 1.7, and 2.2 GeV was elastically scattered off a polarized solid NH 3 target. The asymmetries between the cross section of positive and negative helicity states of the beam were determined. These asymmetries can be used to determine the formmore » factor ratio. In this thesis, we present the asymmetry analysis of the experiment, discuss the main challenges and show preliminary results for part of the data. Preliminary asymmetries indicate an increase in the form factor ratio above unity. However, a complete analysis is required before any conclusion can be made. Further analysis is ongoing, and final asymmetry results and form factor extraction is expected during 2017. We also present first results for 14N asymmetries for elastic and quasi-elastic scattering. The measured asymmetries are in agreement with the shell model approximation, within the low accuracy of the measurement. A change in the asymmetry sign between the elastic and the quasi-elastic processes is seen, and should motivate further theoretical studies. These experimental asymmetries will also be useful for systematic studies of other experiments using polarized NH 3 targets.« less

Comparative study of alkylthiols and alkylamines for the phase transfer of gold nanoparticles from an aqueous phase to n-hexane.

PubMed

Li, Lingxiangyu; Leopold, Kerstin; Schuster, Michael

2013-05-01

An efficient ligand-assisted phase transfer method has been developed to transfer gold nanoparticles (Au-NPs, d: 5-25 nm) from an aqueous solution to n-hexane. Four different ligands, namely 1-dodecanethiol (DDT), 1-octadecanethiol (ODT), dodecylamine (DDA), and octadecylamine (ODA) were investigated, and DDT was found to be the most efficient ligand. It appears that the molar ratio of DDT to Au-NPs is a critical factor affecting the transfer efficiency, and 270-310 is found to be the optimum range, under which the transfer efficiency is >96%. Moreover, the DDT-assisted phase transfer can preserve the shape and size of the Au-NPs, which was confirmed by UV-vis spectra and transmission electron microscopy (TEM). Additionally, the transferred Au-NPs still can be well dispersed in the n-hexane phase and remain stable for at least 2 weeks. On the other hand, the ODT-, DDA-, and ODA-assisted phase transfer is fraught with problems either related to transfer efficiency or NPs aggregation. Overall, the DDT-assisted phase transfer of Au-NPs provides a rapid and efficient method to recover Au-NPs from an aqueous solution to n-hexane. Copyright © 2013 Elsevier Inc. All rights reserved.

Effects of maximum aggregate size on UPV of brick aggregate concrete.

PubMed

Mohammed, Tarek Uddin; Mahmood, Aziz Hasan

2016-07-01

Investigation was carried out to study the effects of maximum aggregate size (MAS) (12.5mm, 19.0mm, 25.0mm, 37.5mm, and 50.0mm) on ultrasonic pulse velocity (UPV) of concrete. For investigation, first class bricks were collected and broken to make coarse aggregate. The aggregates were tested for specific gravity, absorption capacity, unit weight, and abrasion resistance. Cylindrical concrete specimens were made with different sand to aggregate volume ratio (s/a) (0.40 and 0.45), W/C ratio (0.45, 0.50, and 0.55), and cement content (375kg/m(3) and 400kg/m(3)). The specimens were tested for compressive strength and Young's modulus. UPV through wet specimen was measured using Portable Ultrasonic Non-destructive Digital Indicating Tester (PUNDIT). Results indicate that the pulse velocity through concrete increases with an increase in MAS. Relationships between UPV and compressive strength; and UPV and Young's modulus of concrete are proposed for different maximum sizes of brick aggregate. Copyright © 2016 Elsevier B.V. All rights reserved.

Memantine inhibits β-amyloid aggregation and disassembles preformed β-amyloid aggregates.

PubMed

Takahashi-Ito, Kaori; Makino, Mitsuhiro; Okado, Keiko; Tomita, Taisuke

2017-11-04

Memantine, an uncompetitive glutamatergic N-methyl-d-aspartate (NMDA) receptor antagonist, is widely used as a medication for the treatment of Alzheimer's disease (AD). We previously reported that chronic treatment of AD with memantine reduces the amount of insoluble β-amyloid (Aβ) and soluble Aβ oligomers in animal models of AD. The mechanisms by which memantine reduces Aβ levels in the brain were evaluated by determining the effect of memantine on Aβ aggregation using thioflavin T and transmission electron microscopy. Memantine inhibited the formation of Aβ(1-42) aggregates in a concentration-dependent manner, whereas amantadine, a structurally similar compound, did not affect Aβ aggregation at the same concentrations. Furthermore, memantine inhibited the formation of different types of Aβ aggregates, including Aβs carrying familial AD mutations, and disaggregated preformed Aβ(1-42) fibrils. These results suggest that the inhibition of Aβ aggregation and induction of Aβ disaggregation may be involved in the mechanisms by which memantine reduces Aβ deposition in the brain. Copyright © 2017 Elsevier Inc. All rights reserved.

Understanding sexual harassment using aggregate construct models.

PubMed

Nye, Christopher D; Brummel, Bradley J; Drasgow, Fritz

2014-11-01

Sexual harassment has received a substantial amount of empirical attention over the past few decades, and this research has consistently shown that experiencing these behaviors has a detrimental effect on employees' well-being, job attitudes, and behaviors at work. However, these findings, and the conclusions that are drawn from them, make the implicit assumption that the empirical models used to examine sexual harassment are properly specified. This article presents evidence that properly specified aggregate construct models are more consistent with theoretical structures and definitions of sexual harassment and can result in different conclusions about the nomological network of harassment. Results from 3 large samples, 2 military and 1 from a civilian population, are used to illustrate the differences between aggregate construct and reflective indicator models of sexual harassment. These analyses suggested that the factor structure and the nomological network of sexual harassment differ when modeling harassment as an aggregate construct. The implications of these results for the continued study of sexual harassment are discussed. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

Nucleon form factors in generalized parton distributions at high momentum transfers

NASA Astrophysics Data System (ADS)

Sattary Nikkhoo, Negin; Shojaei, Mohammad Reza

2018-05-01

This paper aims at calculating the elastic form factors for a nucleon by considering the extended Regge and modified Gaussian ansatzes based on the generalized parton distributions. To reach this goal, we have considered three different parton distribution functions (PDFs) and have compared the obtained results among them for high momentum transfer ranges. Minimum free parameters have been applied in our parametrization. After achieving the form factors, we calculate the electric radius and the transversely unpolarized and polarized densities for the nucleon. Furthermore, we obtain the impact-parameter-dependent PDFs. Finally, we compare our obtained data with the results of previous studies.

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)

Metal concentrations in aggregate interiors, exteriors, whole aggregates, and bulk of Costa Rican soils

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

Wilcke, W.; Kretzschmar, S.; Bundt, M.

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. Allmore » 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.« less

Physical and mechanical properties of mortars containing PET and PC waste aggregates.

PubMed

Hannawi, Kinda; Kamali-Bernard, Siham; Prince, William

2010-11-01

Non-biodegradable plastic aggregates made of polycarbonate (PC) and polyethylene terephthalate (PET) waste are used as partial replacement of natural aggregates in mortar. Various volume fractions of sand 3%, 10%, 20% and 50% are replaced by the same volume of plastic. This paper investigates the physical and mechanical properties of the obtained composites. The main results of this study show the feasibility of the reuse of PC and PET waste aggregates materials as partial volume substitutes for natural aggregates in cementitious materials. Despite of some drawbacks like a decrease in compressive strength, the use of PC and PET waste aggregates presents various advantages. A reduction of the specific weight of the cementitious materials and a significant improvement of their post-peak flexural behaviour are observed. The calculated flexural toughness factors increase significantly with increasing volume fraction of PET and PC-aggregates. Thus, addition of PC and PET plastic aggregates in cementitious materials seems to give good energy absorbing materials which is very interesting for several civil engineering applications like structures subjected to dynamic or impact efforts. The present study has shown quite encouraging results and opened new way for the recycling of PC waste aggregate in cement and concrete composites. Copyright © 2010 Elsevier Ltd. All rights reserved.

Environmental aspects and renewable energy sources in the production of construction aggregate

NASA Astrophysics Data System (ADS)

Skrzypczak, Izabela; Kokoszka, Wanda; Buda-Ożóg, Lidia; Kogut, Janusz; Słowik, Marta

2017-11-01

The main activity of open pit mining of aggregates are aggregates' exploitation of natural mineral deposits and its modification in order to obtain high-quality aggregates. The development of aggregate production is conditioned by a number of factors. The most important are: documented material resources, mining and manufacturing capabilities, the need of environmental protection (environmental aspects), the subordination of the plan of spatial development, formal and legal issues, as well as economic and financial aspects. While identifying and assessing the environmental impacts of manufacturing aggregates one may distinguish those environmental aspects that have or may have the greatest magnitude of the impact on the environment as a result of industrial activities. Manufacturers producing aggregates located in the areas covered by the special environmental protection require extra diligence in the conduct of mining activities for preservation of natural resources. The article discusses some main environmental aspects of the production of construction aggregates on the example of one of the largest producers of this material in Subcarpathian province of Poland. Environmental protection in production of aggregates may refer to four aspects: the use of natural resources, having excluded land from agriculture and forestry, land reclamation after exploitation, and use of energy from renewable energy sources. The economic and environmental impact of production volume of aggregates is evaluated by the index information capacity method and the method of graphs.

[Factors affecting the clinical pregnancy rate in an in vitro fertilization and embryo transfer program].

PubMed

Zhang, L; Wei, Z; Liu, P

1998-12-01

To analyze the various factors in an in vitro fertilization and embryo transfer (IVF-ET) program which may affect the clinical pregnacy rate. A retrospective study was done on 559 IVF-ET cycles from 1992-Nov. 1995. The indication for treatment was bilateral tubal blockage. The chi 2 analysis of single factor variants with SPSS-PC + V3.0 was used for statistics. The overall clinical pregnancy rate in 559 cycles was 21.6%. The cause of tubal blockage due to tuberculoses consisted of 28.4%, and 34.9% of secondary sterility had the history of artificial abortion. The changes of environment, the different causes of tubal blockage, the history of previous intrauterine pregnancy did not affect the clinical pregnancy rate. When the number of embryos transferred increased to 5, the clinical pregnancy rate was highest 32.5%. The cumulative embryo score or embryo quality was related significantly with clinical pregnancy rate. The number and quality of embryos transferred are important factors affecting the clinical pregnancy rate. However, measures to prevent high-order multiple pregnancy and studies on the survival potential of embryos besides their morphology should be emphasized.

Soil aggregation, erodibility, and erosion rates in mountain soils (NW Alps, Italy)

NASA Astrophysics Data System (ADS)

Stanchi, S.; Falsone, G.; Bonifacio, E.

2015-04-01

Erosion is a relevant soil degradation factor in mountain agrosilvopastoral ecosystems that can be enhanced by the abandonment of agricultural land and pastures left to natural evolution. The on-site and off-site consequences of soil erosion at the catchment and landscape scale are particularly relevant and may affect settlements at the interface with mountain ecosystems. RUSLE (Revised Universal Soil Loss Equation) estimates of soil erosion consider, among others, the soil erodibility factor (K), which depends on properties involved in structure and aggregation. A relationship between soil erodibility and aggregation should therefore be expected. However, erosion may limit the development of soil structure; hence aggregates should not only be related to erodibility but also partially mirror soil erosion rates. The aim of the research was to evaluate the agreement between aggregate stability and erosion-related variables and to discuss the possible reasons for discrepancies in the two kinds of land use considered (forest and pasture). Topsoil horizons were sampled in a mountain catchment under two vegetation covers (pasture vs. forest) and analyzed for total organic carbon, total extractable carbon, pH, and texture. Soil erodibility was computed, RUSLE erosion rate was estimated, and aggregate stability was determined by wet sieving. Aggregation and RUSLE-related parameters for the two vegetation covers were investigated through statistical tests such as ANOVA, correlation, and regression. Soil erodibility was in agreement with the aggregate stability parameters; i.e., the most erodible soils in terms of K values also displayed weaker aggregation. Despite this general observation, when estimating K from aggregate losses the ANOVA conducted on the regression residuals showed land-use-dependent trends (negative average residuals for forest soils, positive for pastures). Therefore, soil aggregation seemed to mirror the actual topsoil conditions better than soil

Effect of lightweight aggregates prepared from fly ash on lightweight concrete performances

NASA Astrophysics Data System (ADS)

Punlert, S.; Laoratanakul, P.; Kongdee, R.; Suntako, R.

2017-09-01

Lightweight aggregates were prepared from fly ash of by-products from the paper industry. The influence of the ratio of clay to fly ash and processing conditions on lightweight aggregates properties were investigated. It was found that the amount of fly ash directly affected to porosity of lightweight aggregates. Lightweight aggregates with the ratio of clay to fly ash at 80:20 wt% using the sintering temperature at 1210°C exhibits bulk density of 1.66 g cm-3, compressive strength of 25 MPa and water absorption of 0.55%. The replacement of coarse aggregates with lightweight aggregates at 100 wt% for concrete production showed the ultimate properties of concrete with density of 1780 g cm-3, water absorption of 3.55%, compressive strength of 40.94 MPa and thermal conductivity of 0.77 W m-1K-1. The concrete had more than 25% weight reduction while keeping a similar compressive strength to an ordinary concrete. This is revealed that lightweight aggregates could be applied into structural concrete because it was able to reduce work load and increase safety factor of construction.

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

USGS Publications Warehouse

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

1995-01-01

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

Environment‐Adaptive Coassembly/Self‐Sorting and Stimulus‐Responsiveness Transfer Based on Cholesterol Building Blocks

PubMed Central

Xing, Pengyao; Tham, Huijun Phoebe; Li, Peizhou; Chen, Hongzhong; Xiang, Huijing

2017-01-01

Abstract Manipulating the property transfer in nanosystems is a challenging task since it requires switchable molecular packing such as separate aggregation (self‐sorting) or synergistic aggregation (coassembly). Herein, a unique manipulation of self‐sorting/coassembly aggregation and the observation of switchable stimulus‐responsiveness transfer in a two component self‐assembly system are reported. Two building blocks bearing the same cholesterol group give versatile topological structures in polar and nonpolar solvents. One building block (cholesterol conjugated cynanostilbene, CCS) consists of cholesterol conjugated with a cynanostilbene unit, and the other one (C10CN) is comprised of cholesterol connected with a naphthalimide group having a flexible long alkyl chain. Their assemblies including gel, crystalline plates, and vesicles are obtained. In gel and crystalline plate phases, the self‐sorting behavior dominates, while synergistic coassembly occurs in vesicle phase. Since CCS having the cyanostilbene group can respond to the light irradiation, it undergoes light‐induced chiral amplification. C10CN is thermally responsive, whereby its supramolecular chirality is inversed upon heating. In coassembled vesicles, it is interestingly observed that their responsiveness can be transferred by each other, i.e., the C10CN segment is sensitive to the light irradiation, while CCS is thermoresponsive. This unprecedented behavior of the property transfer may shine a light to the precise fabrication of smart materials. PMID:29375976

Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

NASA Astrophysics Data System (ADS)

Cadena, M. S. Reyes; Chapul, L. Sánchez; Pérez, Javiér; García, M. N. Jiménez; López, M. A. Jiménez; Espíndola, M. E. Sánchez; Perez, R. Paniagua; Hernández, N. A.; Paniagua, G.; Uribe, F.; Nava, J. J. Godina; Segura, M. A. Rodríguez

2008-08-01

We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-β) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animals subjected to ELF together with the transfer factor.

INVESTIGATION OF TRANSFER OF FLUORESCENT TRACERS FROM SURFACES TO SKIN

EPA Science Inventory

Under the provisions of the Food Quality Protection Act (FQPA), aggregate exposure assessments must be conducted for pesticides proposed for registration. Many aspects of dermal exposure assessment remain poorly quantified. For purposes of assessing surface-to-skin transfers ...

Natural convection during heat energy accumulation by substances that change their state of aggregation

NASA Astrophysics Data System (ADS)

Chukaev, A. G.; Kuks, A. M.

Heat transfer calculations are presented for a heat accumulator using the melting heat of a substance which changes its state of aggregation. It is shown that the approach adopted here makes it possible to evaluate the efficiency of using heat-storage materials in the pipe-tank system. The calculations, which allow for the effect of free convection in the liquid phase, have been made using the Boussinesq approximation. Results of a numerical experiment for NaNO3 salt show that the effect of natural convection on heat transfer is significant and that the heat flux to the material decreases as heat accumulates.

Aggregating indices of risk and protection for adolescent behavior problems: the Communities That Care Youth Survey.

PubMed

Feinberg, Mark E; Ridenour, Ty A; Greenberg, Mark T

2007-06-01

To facilitate research on adolescent risk and protection regarding behavior problems, and to facilitate community decision-making regarding resource allocation for intervention programs, by creating a reduced set of coherent aggregate indices of adolescent risk and protection. We examined the 31 risk and protective factor scales in the Communities That Care Youth Survey (CTC-YS). Data came from two waves of the CTC-YS administered to sixth through 12th graders in Pennsylvania (2001 n = 43,842; 2003 n =101,988). Factor analysis and calculation of internal reliability were used to create aggregate indices of risk/protective factor domains. Correlations of aggregate indices with each other and with problem behaviors (antisocial behavior, substance use) were examined. Theory and empirical results led to the creation of seven coherent indices: Community Cohesion, Family Cohesion, Family Risk, School Support for Prosocial Activities, Antisocial Peer Domain, Attitudes toward Risky Behavior, Risky Behavioral Tendencies. Four scales were not included in the aggregate index (Religiosity, Academic Performance, Personal Transitions and Mobility, and Early Initiation of Drug Use and Antisocial Behavior). The indices were related to each other and to adolescent problem behaviors (antisocial behavior and substance use) in expected ways. Results were consistent across waves of data. The construction of theoretically meaningful and empirically defensible aggregate measures of adolescent risk and protective factors is possible, although analyses of other data sets and further discussion are warranted. The use of aggregate indices by researchers and communities is recommended as a way to facilitate research and decision-making.

Free energy landscapes for initiation and branching of protein aggregation.

PubMed

Zheng, Weihua; Schafer, Nicholas P; Wolynes, Peter G

2013-12-17

Experiments on artificial multidomain protein constructs have probed the early stages of aggregation processes, but structural details of the species that initiate aggregation remain elusive. Using the associative-memory, water-mediated, structure and energy model known as AWSEM, a transferable coarse-grained protein model, we performed simulations of fused constructs composed of up to four copies of the Titin I27 domain or its mutant I27* (I59E). Free energy calculations enable us to quantify the conditions under which such multidomain constructs will spontaneously misfold. Consistent with experimental results, the dimer of I27 is found to be the smallest spontaneously misfolding construct. Our results show how structurally distinct misfolded states can be stabilized under different thermodynamic conditions, and this result provides a plausible link between the single-molecule misfolding experiments under native conditions and aggregation experiments under denaturing conditions. The conditions for spontaneous misfolding are determined by the interplay among temperature, effective local protein concentration, and the strength of the interdomain interactions. Above the folding temperature, fusing additional domains to the monomer destabilizes the native state, and the entropically stabilized amyloid-like state is favored. Because it is primarily energetically stabilized, the domain-swapped state is more likely to be important under native conditions. Both protofibril-like and branching structures are found in annealing simulations starting from extended structures, and these structures suggest a possible connection between the existence of multiple amyloidogenic segments in each domain and the formation of branched, amorphous aggregates as opposed to linear fibrillar structures.

A Transfer Learning Approach for Applying Matrix Factorization to Small ITS Datasets

ERIC Educational Resources Information Center

Voß, Lydia; Schatten, Carlotta; Mazziotti, Claudia; Schmidt-Thieme, Lars

2015-01-01

Machine Learning methods for Performance Prediction in Intelligent Tutoring Systems (ITS) have proven their efficacy; specific methods, e.g. Matrix Factorization (MF), however suffer from the lack of available information about new tasks or new students. In this paper we show how this problem could be solved by applying Transfer Learning (TL),…

Aggregation of TiO2-graphene nanocomposites in aqueous environment: Influence of environmental factors and UV irradiation.

PubMed

Hua, Zulin; Zhang, Jianan; Bai, Xue; Ye, Zhengfang; Tang, Zhiqiang; Liang, Lu; Liu, Yuqi

2016-01-01

The aggregation kinetics of TiO2-graphene nanocomposites in aqueous solution affected by solution pH, salt types (NaCl, CaCl2) and concentrations of electrolytes, and stability induced by UV irradiation was investigated in this study. The zeta potentials and hydrodynamic diameter of the nanoparticles were used as bases to assess the aggregation behavior, and stability of nanocomposites exposed to UV irradiation was expressed in terms of supernatant concentration. The aggregation of TiO2-graphene nanoparticles in aqueous media followed the colloidal theory. TiO2-graphene nanoparticles were significantly aggregated in the presence of a diavalent cation compared with monovalent cation because the former was more capable of effective charge screening and neutralization. The calculated Hamaker constant of the TiO2-graphene nanocomposites in aqueous solution prepared in the lab was 2.31×10(-20)J. The stability of this composite nanoparticles was between those of pure TiO2 and graphene. A known intensity of UV irradiation was beneficial in the formation of TiO2-graphene nanoparticle aggregates. However, prolonged UV irradiation may stabilize the nanoparticles. These results provided critical information about the colloidal properties of the new TiO2-graphene nanocomposites and were useful in predicting the fate and transport of TiO2-graphene nanocomposites in natural water environments. Copyright © 2015 Elsevier B.V. All rights reserved.

Investigating the feasibility of scale up and automation of human induced pluripotent stem cells cultured in aggregates in feeder free conditions☆

PubMed Central

Soares, Filipa A.C.; Chandra, Amit; Thomas, Robert J.; Pedersen, Roger A.; Vallier, Ludovic; Williams, David J.

2014-01-01

The transfer of a laboratory process into a manufacturing facility is one of the most critical steps required for the large scale production of cell-based therapy products. This study describes the first published protocol for scalable automated expansion of human induced pluripotent stem cell lines growing in aggregates in feeder-free and chemically defined medium. Cells were successfully transferred between different sites representative of research and manufacturing settings; and passaged manually and using the CompacT SelecT automation platform. Modified protocols were developed for the automated system and the management of cells aggregates (clumps) was identified as the critical step. Cellular morphology, pluripotency gene expression and differentiation into the three germ layers have been used compare the outcomes of manual and automated processes. PMID:24440272

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

PubMed

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

2015-01-01

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

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

PubMed

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

2016-04-01

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

Platelet activation and aggregation by the opportunistic pathogen Cutibacterium (Propionibacterium) acnes

PubMed Central

Petersson, Frida; Kilsgård, Ola; Shannon, Oonagh

2018-01-01

Cutibacterium (Propionibacterium) acnes, considered a part of the skin microbiota, is one of the most commonly isolated anaerobic bacteria from medical implants in contact with plasma. However, the precise interaction of C. acnes with blood cells and plasma proteins has not been fully elucidated. Herein, we have investigated the molecular interaction of C. acnes with platelets and plasma proteins. We report that the ability of C. acnes to aggregate platelets is dependent on phylotype, with a significantly lower ability amongst type IB isolates, and the interaction of specific donor-dependent plasma proteins (or concentrations thereof) with C. acnes. Pretreatment of C. acnes with plasma reduces the lag time before aggregation demonstrating that pre-deposition of plasma proteins on C. acnes is an important step in platelet aggregation. Using mass spectrometry we identified several plasma proteins deposited on C. acnes, including IgG, fibrinogen and complement factors. Inhibition of IgG, fibrinogen or complement decreased C. acnes-mediated platelet aggregation, demonstrating the importance of these plasma proteins for aggregation. The interaction of C. acnes and platelets was visualized using fluorescence microscopy, verifying the presence of IgG and fibrinogen as components of the aggregates, and co-localization of C. acnes and platelets in the aggregates. Here, we have demonstrated the ability of C. acnes to activate and aggregate platelets in a bacterium and donor-specific fashion, as well as added mechanistic insights into this interaction. PMID:29385206

Platelet activation and aggregation by the opportunistic pathogen Cutibacterium (Propionibacterium) acnes.

PubMed

Petersson, Frida; Kilsgård, Ola; Shannon, Oonagh; Lood, Rolf

2018-01-01

Cutibacterium (Propionibacterium) acnes, considered a part of the skin microbiota, is one of the most commonly isolated anaerobic bacteria from medical implants in contact with plasma. However, the precise interaction of C. acnes with blood cells and plasma proteins has not been fully elucidated. Herein, we have investigated the molecular interaction of C. acnes with platelets and plasma proteins. We report that the ability of C. acnes to aggregate platelets is dependent on phylotype, with a significantly lower ability amongst type IB isolates, and the interaction of specific donor-dependent plasma proteins (or concentrations thereof) with C. acnes. Pretreatment of C. acnes with plasma reduces the lag time before aggregation demonstrating that pre-deposition of plasma proteins on C. acnes is an important step in platelet aggregation. Using mass spectrometry we identified several plasma proteins deposited on C. acnes, including IgG, fibrinogen and complement factors. Inhibition of IgG, fibrinogen or complement decreased C. acnes-mediated platelet aggregation, demonstrating the importance of these plasma proteins for aggregation. The interaction of C. acnes and platelets was visualized using fluorescence microscopy, verifying the presence of IgG and fibrinogen as components of the aggregates, and co-localization of C. acnes and platelets in the aggregates. Here, we have demonstrated the ability of C. acnes to activate and aggregate platelets in a bacterium and donor-specific fashion, as well as added mechanistic insights into this interaction.

Assessing the role of aromatic residues in the amyloid aggregation of human muscle acylphosphatase

PubMed Central

Bemporad, Francesco; Taddei, Niccolò; Stefani, Massimo; Chiti, Fabrizio

2006-01-01

Among the many parameters that have been proposed to promote amyloid fibril formation is the π-stacking of aromatic residues. We have studied the amyloid aggregation of several mutants of human muscle acylphosphatase in which an aromatic residue was substituted with a non-aromatic one. The aggregation rate was determined using the Thioflavin T test under conditions in which the variants populated initially an ensemble of partially unfolded conformations. Substitutions in aggregation-promoting fragments of the sequence result in a dramatically decreased aggregation rate of the protein, confirming the propensity of aromatic residues to promote this process. Nevertheless, a statistical analysis shows that the measured decrease of aggregation rate following mutation arises predominantly from a reduction of hydrophobicity and intrinsic β-sheet propensity. This suggests that aromatic residues favor aggregation because of these factors rather than for their aromaticity. PMID:16600970

Estimation of polydispersity in aggregating red blood cells by quantitative ultrasound backscatter analysis.

PubMed

de Monchy, Romain; Rouyer, Julien; Destrempes, François; Chayer, Boris; Cloutier, Guy; Franceschini, Emilie

2018-04-01

Quantitative ultrasound techniques based on the backscatter coefficient (BSC) have been commonly used to characterize red blood cell (RBC) aggregation. Specifically, a scattering model is fitted to measured BSC and estimated parameters can provide a meaningful description of the RBC aggregates' structure (i.e., aggregate size and compactness). In most cases, scattering models assumed monodisperse RBC aggregates. This study proposes the Effective Medium Theory combined with the polydisperse Structure Factor Model (EMTSFM) to incorporate the polydispersity of aggregate size. From the measured BSC, this model allows estimating three structural parameters: the mean radius of the aggregate size distribution, the width of the distribution, and the compactness of the aggregates. Two successive experiments were conducted: a first experiment on blood sheared in a Couette flow device coupled with an ultrasonic probe, and a second experiment, on the same blood sample, sheared in a plane-plane rheometer coupled to a light microscope. Results demonstrated that the polydisperse EMTSFM provided the best fit to the BSC data when compared to the classical monodisperse models for the higher levels of aggregation at hematocrits between 10% and 40%. Fitting the polydisperse model yielded aggregate size distributions that were consistent with direct light microscope observations at low hematocrits.

α-Synuclein propagates from mouse brain to grafted dopaminergic neurons and seeds aggregation in cultured human cells

PubMed Central

Hansen, Christian; Angot, Elodie; Bergström, Ann-Louise; Steiner, Jennifer A.; Pieri, Laura; Paul, Gesine; Outeiro, Tiago F.; Melki, Ronald; Kallunki, Pekka; Fog, Karina; Li, Jia-Yi; Brundin, Patrik

2011-01-01

Post-mortem analyses of brains from patients with Parkinson disease who received fetal mesencephalic transplants show that α-synuclein–containing (α-syn–containing) Lewy bodies gradually appear in grafted neurons. Here, we explored whether intercellular transfer of α-syn from host to graft, followed by seeding of α-syn aggregation in recipient neurons, can contribute to this phenomenon. We assessed α-syn cell-to-cell transfer using microscopy, flow cytometry, and high-content screening in several coculture model systems. Coculturing cells engineered to express either GFP– or DsRed-tagged α-syn resulted in a gradual increase in double-labeled cells. Importantly, α-syn–GFP derived from 1 neuroblastoma cell line localized to red fluorescent aggregates in other cells expressing DsRed–α-syn, suggesting a seeding effect of transmitted α-syn. Extracellular α-syn was taken up by cells through endocytosis and interacted with intracellular α-syn. Next, following intracortical injection of recombinant α-syn in rats, we found neuronal uptake was attenuated by coinjection of an endocytosis inhibitor. Finally, we demonstrated in vivo transfer of α-syn between host cells and grafted dopaminergic neurons in mice overexpressing human α-syn. In summary, intercellularly transferred α-syn interacts with cytoplasmic α-syn and can propagate α-syn pathology. These results suggest that α-syn propagation is a key element in the progression of Parkinson disease pathology. PMID:21245577

Plasmonic properties and enhanced fluorescence of gold and dye-doped silica nanoparticle aggregates

NASA Astrophysics Data System (ADS)

Green, Nathaniel Scott

The development of metal-enhanced fluorescence has prompted a great interest in augmenting the photophysical properties of fluorescent molecules with noble metal nanostructures. Our research efforts, outlined in this dissertation, focus on augmenting properties of fluorophores by conjugation with gold nanostructures. The project goals are split into two separate efforts; the enhancement in brightness of fluorophores and long distance non-radiative energy transfer between fluorophores. We believe that interacting dye-doped silica nanoparticles with gold nanoparticles can facilitate both of these phenomena. Our primary research interest is focused on optimizing brightness, as this goal should open a path to studying the second goal of non-radiative energy transfer. The two major challenges to this are constructing suitable nanomaterials and functionalizing them to promote plasmonically active complexes. The synthesis of dye-doped layered silica nanoparticles allows for control over the discrete location of the dye and a substrate that can be surface functionalized. Controlling the exact location of the dye is important to create a silica spacer, which promotes productive interactions with metal nanostructures. Furthermore, the synthesis of silica nanoparticles allows for various fluorophores to be studied in similar environments (removing solvent and other chemo-sensitive issues). Functionalizing the surface of silica nanoparticles allows control over the degree of silica and gold nanoparticle aggregation in solution. Heteroaggregation in solution is useful for producing well-aggregated clusters of many gold around a single silica nanoparticle. The dye-doped surface functionalized silica nanoparticles can than be mixed efficiently with gold nanomaterials. Aggregating multiple gold nanospheres around a single dye-doped silica nanoparticle can dramatically increase the fluorescent brightness of the sample via metal-enhanced fluorescence due to increase plasmonic

Aggregation and breakup of colloidal particle aggregates in shear flow, studied with video microscopy.

PubMed

Tolpekin, V A; Duits, M H G; van den Ende, D; Mellema, J

2004-03-30

We used video microscopy to study the behavior of aggregating suspensions in shear flow. Suspensions consisted of 920 nm diameter silica spheres, dispersed in a methanol/bromoform solvent, to which poly(ethylene glycol) (M = 35.000 g) was added to effect weak particle aggregation. With our solvent mixture, the refractive index of the particles could be closely matched, to allow microscopic observations up to 80 microm deep into the suspension. Also the mass density is nearly equal to that of the particles, thus allowing long observation times without problems due to aggregate sedimentation. Particles were visualized via fluorescent molecules incorporated into their cores. Using a fast confocal scanning laser microscope made it possible to characterize the (flowing) aggregates via their contour-area distributions as observed in the focal plane. The aggregation process was monitored from the initial state (just after adding the polymer), until a steady state was reached. The particle volume fraction was chosen at 0.001, to obtain a characteristic aggregation time of a few hundred seconds. On variation of polymer concentration, cP (2.2-12.0 g/L), and shear rate, gamma (3-6/s), it was observed that the volume-averaged size, Dv, in the steady state became larger with polymer concentration and smaller with shear rate. This demonstrates that the aggregate size is set by a competition between cohesive forces caused by the polymer and rupture forces caused by the flow. Also aggregate size distributions were be measured (semiquantitatively). Together with a description for the internal aggregate structure they allowed a modeling of the complete aggregation curve, from t = 0 up to the steady state. A satisfactory description could be obtained by describing the aggregates as fractal objects, with Df = 2.0, as measured from CSLM images after stopping the flow. In this modeling, the fitted characteristic breakup time was found to increase with cP.

Organic carbon, water repellency and soil stability to slaking at aggregate and intra-aggregate scales

NASA Astrophysics Data System (ADS)

Jordán López, Antonio; García-Moreno, Jorge; Gordillo-Rivero, Ángel J.; Zavala, Lorena M.; Cerdà, Artemi; Alanís, Nancy; Jiménez-Compán, Elizabeth

2015-04-01

Water repellency (WR) is a property of some soils that inhibits or delays water infiltration between a few seconds and days or weeks. Inhibited or delayed infiltration contributes to ponding and increases runoff flow generation, often increasing soil erosion risk. In water-repellent soils, water infiltrates preferentially through cracks or macropores, causing irregular soil wetting patterns, the development of preferential flow paths and accelerated leaching of nutrients. Although low inputs of hydrophobic organic substances and high mineralization rates lead to low degrees of WR in cropped soils, it has been reported that conservative agricultural practices may induce soil WR. Although there are many studies at catchment, slope or plot scales very few studies have been carried out at particle or aggregate scale. Intra-aggregate heterogeneity of physical, biological and chemical properties conditions the transport of substances, microbial activity and biochemical processes, including changes in the amount, distribution and chemical properties of organic matter. Some authors have reported positive relationships between soil WR and aggregate stability, since it may delay the entry of water into aggregates, increase structural stability and contribute to reduce soil erosion risk. Organic C (OC) content, aggregate stability and WR are therefore strongly related parameters. In the case of agricultural soils, where both the type of management as crops can influence all these parameters, it is important to evaluate the interactions among them and their consequences. Studies focused on the intra-aggregate distribution of OC and WR are necessary to shed light on the soil processes at a detailed scale. It is extremely important to understand how the spatial distribution of OC in soil aggregates can protect against rapid water entry and help stabilize larger structural units or lead to preferential flow. The objectives of this research are to study [i] the OC content and the

Real-time imaging of Huntingtin aggregates diverting target search and gene transcription

PubMed Central

Li, Li; Liu, Hui; Dong, Peng; Li, Dong; Legant, Wesley R; Grimm, Jonathan B; Lavis, Luke D; Betzig, Eric; Tjian, Robert; Liu, Zhe

2016-01-01

The presumptive altered dynamics of transient molecular interactions in vivo contributing to neurodegenerative diseases have remained elusive. Here, using single-molecule localization microscopy, we show that disease-inducing Huntingtin (mHtt) protein fragments display three distinct dynamic states in living cells – 1) fast diffusion, 2) dynamic clustering and 3) stable aggregation. Large, stable aggregates of mHtt exclude chromatin and form 'sticky' decoy traps that impede target search processes of key regulators involved in neurological disorders. Functional domain mapping based on super-resolution imaging reveals an unexpected role of aromatic amino acids in promoting protein-mHtt aggregate interactions. Genome-wide expression analysis and numerical simulation experiments suggest mHtt aggregates reduce transcription factor target site sampling frequency and impair critical gene expression programs in striatal neurons. Together, our results provide insights into how mHtt dynamically forms aggregates and disrupts the finely-balanced gene control mechanisms in neuronal cells. DOI: http://dx.doi.org/10.7554/eLife.17056.001 PMID:27484239

Red blood cell aggregation, aggregate strength and oxygen transport potential of blood are abnormal in both homozygous sickle cell anemia and sickle-hemoglobin C disease.

PubMed

Tripette, Julien; Alexy, Tamas; Hardy-Dessources, Marie-Dominique; Mougenel, Daniele; Beltan, Eric; Chalabi, Tawfik; Chout, Roger; Etienne-Julan, Maryse; Hue, Olivier; Meiselman, Herbert J; Connes, Philippe

2009-08-01

Recent evidence suggests that red blood cell aggregation and the ratio of hematocrit to blood viscosity (HVR), an index of the oxygen transport potential of blood, might considerably modulate blood flow dynamics in the microcirculation. It thus seems likely that these factors could play a role in sickle cell disease. We compared red blood cell aggregation characteristics, blood viscosity and HVR at different shear rates between sickle cell anemia and sickle cell hemoglobin C disease (SCC) patients, sickle cell trait carriers (AS) and control individuals (AA). Blood viscosity determined at high shear rate was lower in sickle cell anemia (n=21) than in AA (n=52), AS (n=33) or SCC (n=21), and was markedly increased in both SCC and AS. Despite differences in blood viscosity, both sickle cell anemia and SCC had similar low HVR values compared to both AA and AS. Sickle cell anemia (n=21) and SCC (n=19) subjects had a lower red blood cell aggregation index and longer time for red blood cell aggregates formation than AA (n=16) and AS (n=15), and a 2 to 3 fold greater shear rate required to disperse red blood cell aggregates. The low HVR levels found in sickle cell anemia and SCC indicates a comparable low oxygen transport potential of blood in both genotypes. Red blood cell aggregation properties are likely to be involved in the pathophysiology of sickle cell disease: the increased shear forces needed to disperse red blood cell aggregates may disturb blood flow, especially at the microcirculatory level, since red blood cell are only able to pass through narrow capillaries as single cells rather than as aggregates.

Familial Aggregation and Heritability of Schizophrenia and Co-aggregation of Psychiatric Illnesses in Affected Families.

PubMed

Chou, I-Jun; Kuo, Chang-Fu; Huang, Yu-Shu; Grainge, Matthew J; Valdes, Ana M; See, Lai-Chu; Yu, Kuang-Hui; Luo, Shue-Fen; Huang, Lu-Shuang; Tseng, Wen-Yi; Zhang, Weiya; Doherty, Michael

2017-09-01

Strong familial aggregation of schizophrenia has been reported but there is uncertainty concerning the degree of genetic contribution to the phenotypic variance of the disease. This study aimed to examine the familial aggregation and heritability of schizophrenia, and the relative risks (RRs) of other psychiatric diseases, in relatives of people with schizophrenia using the Taiwan National Health Insurance Database. The study population included individuals with affected first-degree or second-degree relatives identified from all beneficiaries (n = 23 422 955) registered in 2013. Diagnoses of schizophrenia made by psychiatrists were ascertained between January 1, 1996 and December 31, 2013. Having an affected co-twin, first-degree relative, second-degree relative, or spouse was associated with an adjusted RR (95% CI) of 37.86 (30.55-46.92), 6.30 (6.09-6.53), 2.44 (1.91-3.12), and 1.88 (1.64-2.15), respectively. Compared with the general population, individuals with one affected first-degree relative had a RR (95% CI) of 6.00 (5.79-6.22) and those with 2 or more had a RR (95% CI) of 14.66 (13.00-16.53) for schizophrenia. The accountability for the phenotypic variance of schizophrenia was 47.3% for genetic factors, 15.5% for shared environmental factors, and 37.2% for non-shared environmental factors. The RR (95% CI) in individuals with a first-degree relative with schizophrenia was 3.49 (3.34-3.64) for mood disorders and 3.91 (3.35-4.57) for delusional disorders. A family history of schizophrenia is therefore associated with a higher risk of developing schizophrenia, mood disorders, and delusional disorders. Heritability and environmental factors each account for half of the phenotypic variance of schizophrenia. © The Author 2016. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center.

Robotic technology evolution and transfer

NASA Technical Reports Server (NTRS)

Marzwell, Neville I.

1992-01-01

A report concerning technology transfer in the area of robotics is presented in vugraph form. The following topics are discussed: definition of technology innovation and tech-transfer; concepts relevant for understanding tech-transfer; models advanced to portray tech-transfer process; factors identified as promoting tech-transfer; factors identified as impeding tech-transfer; what important roles do individuals fulfill in tech-transfer; federal infrastructure for promoting tech-transfer; federal infrastructure for promoting tech-transfer; robotic technology evolution; robotic technology transferred; and recommendations for successful robotics tech-transfer.

Properties of Concrete with Tire Derived Aggregate Partially Replacing Coarse Aggregates

PubMed Central

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

2015-01-01

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

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.

Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

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

Cadena, M. S. Reyes; Chapul, L. Sanchez; Perez, Javier

2008-08-11

We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-{beta}) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animalsmore » subjected to ELF together with the transfer factor.« less

On the radiative properties of soot aggregates - Part 2: Effects of coating

NASA Astrophysics Data System (ADS)

Liu, Fengshan; Yon, Jérôme; Bescond, Alexandre

2016-03-01

The effects of weakly absorbing material coating on soot have attracted considerable research attention in recent years due to the significant influence of such coating on soot radiative properties and the large differences predicted by different numerical models. Soot aggregates were first numerically generated using the diffusion limited cluster aggregation algorithm to produce fractal aggregates formed by log-normally distributed polydisperse spherical primary particles in point-touch. These aggregates were then processed by adding a certain amount of primary particle overlapping and necking to simulate the soot morphology observed from transmission electron microscopy images. After this process, a layer of WAM coating of different thicknesses was added to these more realistic soot aggregates. The radiative properties of these coated soot aggregates over the spectral range of 266-1064 nm were calculated by the discrete dipole approximation (DDA) using the spectrally dependent refractive index of soot for four aggregates containing Np=1, 20, 51 and 96 primary particles. The considered coating thicknesses range from 0% (no coating) up to 100% coating in terms of the primary particle diameter. Coating enhances both the particle absorption and scattering cross sections, with much stronger enhancement to the scattering one, as well as the asymmetry factor and the single scattering albedo. The absorption enhancement is stronger in the UV than in the visible and the near infrared. The simple corrections to the Rayleigh-Debye-Gans fractal aggregates theory for uncoated soot aggregates are found not working for coated soot aggregates. The core-shell model significantly overestimates the absorption enhancement by coating in the visible and the near infrared compared to the DDA results of the coated soot particle. Treating an externally coated soot aggregate as an aggregate formed by individually coated primary particles significantly underestimates the absorption

The economic mobility in money transfer models

NASA Astrophysics Data System (ADS)

Ding, Ning; Xi, Ning; Wang, Yougui

2006-07-01

In this paper, we investigate the economic mobility in four money transfer models which have been applied into the research on wealth distribution. We demonstrate the mobility by recording the time series of agents’ ranks and observing their volatility. We also compare the mobility quantitatively by employing an index, “the per capita aggregate change in log-income”, proposed by economists. Like the shape of distribution, the character of mobility is also decided by the trading rule in these transfer models. It is worth noting that even though two models have the same type of distribution, their mobility characters may be quite different.

Methods of predicting aggregate voids.

DOT National Transportation Integrated Search

2013-03-01

Percent voids in combined aggregates vary significantly. Simplified methods of predicting aggregate : voids were studied to determine the feasibility of a range of gradations using aggregates available in Kansas. : The 0.45 Power Curve Void Predictio...

Blended aggregate study : final report.

DOT National Transportation Integrated Search

1980-03-01

Louisiana produces no naturally occurring skid resistant aggregate and, therefore, must import these aggregates at great expense. : In an effort to extend the yield of these aggregates, a laboratory investigation was initiated to determine the feasib...

Properties of concrete blocks prepared with low grade recycled aggregates.

PubMed

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

2009-08-01

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

The C-Terminal Threonine of Aβ43 Nucleates Toxic Aggregation via Structural and Dynamical Changes in Monomers and Protofibrils

PubMed Central

2015-01-01

Recent studies suggest that deposition of amyloid β (Aβ) into oligomeric aggregates and fibrils, hallmarks of Alzheimer’s disease, may be initiated by the aggregation of Aβ species other than the well-studied 40- and 42-residue forms, Aβ40 and Aβ42, respectively. Here we report on key structural, dynamic, and aggregation kinetic parameters of Aβ43, extended by a single threonine at the C-terminus relative to Aβ42. Using aggregation time course experiments, electron microscopy, and a combination of nuclear magnetic resonance measurements including backbone relaxation, dark-state exchange saturation transfer, and quantification of chemical shift differences and scalar coupling constants, we demonstrate that the C-terminal threonine in Aβ43 increases the rate and extent of protofibril aggregation and confers slow C-terminal motions in the monomeric and protofibril-bound forms of Aβ43. Relative to the neighboring residues, the hydrophilic Thr43 of Aβ43 favors direct contact with the protofibril surface more so than the C-terminus of Aβ40 or Aβ42. Taken together, these results demonstrate the potential of a small chemical modification to affect the properties of Aβ structure and aggregation, providing a mechanism for the potential role of Aβ43 as a primary nucleator of Aβ aggregates in Alzheimer’s disease. PMID:24773532

Temperature dependent rapid annealing effect induces amorphous aggregation of human serum albumin.

PubMed

Ishtikhar, Mohd; Ali, Mohd Sajid; Atta, Ayman M; Al-Lohedan, Hammad; Badr, Gamal; Khan, Rizwan Hasan

2016-01-01

This study represents an analysis of the thermal aggregation of human serum albumin (HSA) induced by novel rosin modified compounds. The aggregation process causes conformational alterations in the secondary and tertiary structures of the proteins. The conversion of globular protein to amorphous aggregates was carried out by spectroscopic, calorimetric and microscopic techniques to investigate the factors that are responsible for the structural, conformational and morphological alteration in the protein. Our outcome results show that the aggregation of HSA was dependent on the hydrophobicity, charge and temperature, because the formation of amorphous aggregates occurs in the presence of a novel cationic rosin compound, quaternary amine of rosin diethylaminoethyl ester (QRMAE), at 40°C and pH 7.4 (but at 25°C on similar pH value, there was no evidence of aggregate formation). In addition, the parent compound of QRMAE, i.e., abietic acid, and other derivatives such as nonionic rosin compounds [(RMPEG-750) and (RMA-MPEG-750)] do not shows the aggregating property. This work provides precise and necessary information that aid in the understanding the effects of rosin derivative compounds on HSA. This study also restrains important information for athletes, health providers, pharmaceutical companies, industries, and soft drink-processing companies. Copyright © 2015 Elsevier B.V. All rights reserved.

Non-pathogenic protein aggregates in skeletal muscle in MLF1 transgenic mice.

PubMed

Li, Zhi-Fang; Wu, Xiaohua; Jiang, Yun; Liu, Jianxiang; Wu, Chun; Inagaki, Masaki; Izawa, Ichiro; Mizisin, Andrew P; Engvall, Eva; Shelton, G Diane

2008-01-15

Protein aggregate formation in muscle is thought to be pathogenic and associated with clinical weakness. Over-expression of either wild type or a mutant form of myeloid leukemia factor 1 (MLF1) in transgenic mouse skeletal muscle and in cultured cells resulted in aggregate formation. Aggregates were detected in MLF1 transgenic mice at 6 weeks of age, and increased in size with age. However, histological examination of skeletal muscles of MLF1 transgenic mice revealed no pathological changes other than the aggregates, and RotaRod testing did not detect functional deficits. MLF1 has recently been identified as a protein that could neutralize the toxicity of intracellular protein aggregates in a Drosophila model of Huntington's disease (HD). We also demonstrate that MLF1 interacts with MRJ, a heat shock protein, which can independently neutralize the toxicity of intracellular protein aggregates in the Drosophila HD model. Our data suggest that over-expression of MLF1 has no significant impact on skeletal muscle function in mice; that progressive formation of protein aggregates in muscle are not necessarily pathogenic; and that MLF1 and MRJ may function together to ameliorate the toxic effects of polyglutamine or mutant proteins in myodegenerative diseases such as inclusion body myositis and oculopharyngeal muscular dystrophy, as well as neurodegenerative disease.

Soil aggregation and aggregate-associated carbon under four typical halophyte communities in an arid area.

PubMed

Yang, Haichang; Wang, Jingya; Zhang, Fenghua

2016-12-01

The soil microbial biomass carbon (MBC) is considered as a sensitive index of soil carbon ecosystem. The distribution of aggregate-associated MBC determines the capacity of the soil to store soil organic carbon (SOC). We compared soil aggregate-associated SOC and aggregate-associated MBC under four halophyte communities: Karelinia caspia (Pall.) Less. (Abbr. K. caspia), Bassia dasyphylla (Fisch. et C. A. Mey.) Kuntze. (Abbr. B. dasyphylla), Haloxylon ammodendron (C. A. Mey.) Bunge. (Abbr. H. ammodendron), and Tamarix ramosissima Lour (Abbr. T. ramosissima) on an alluvial fan in the Manasi River Basin, Xinjiang, China. The specific objectives of the study were to determine which aggregate size fraction was the most important for MBC and SOC retention in these soils of four halophyte communities. The results showed that the 0.053-0.25 mm fraction contained 47 to 75 % of the total soil mass. The amount of soil in the 0.053-0.25 mm fraction was significantly greater than that in the >0.25 and the <0.053 mm fractions. The >0.25 and the <0.053 mm fractions contained 7.8 to 43.0 % of the soil mass. Aggregate-associated SOC concentrations ranged from 1.70 to 13.68 g kg -1 , and the aggregate-associated SOC were the highest under the H. ammodendron and T. ramosissima communities. The aggregate-associated MBC ranged from 55.26 to 217.11 g kg -1 , and the aggregate-associated MBC were higher under the K. caspia and B. dasyphylla communities. The aggregate-associated SOC concentrations were significantly higher in the >0.25 and the <0.053 mm fractions than in the 0.053-0.25 mm fraction. The aggregate-associated MBC in the 20-40 cm depth was consistent with its law. However, in the 0-20 cm depth, the aggregate-associated MBC concentrations were significantly higher in the >0.25 mm fraction than the other two aggregate fractions, and there were no significant differences in 0.25-0.053 or <0.053 mm fraction. Correlation analyses showed that the aggregate

Factors Contributing to the Upward Transfer of Baccalaureate Aspirants Beginning at Community Colleges

ERIC Educational Resources Information Center

Wang, Xueli

2012-01-01

This study examined factors associated with the upward transfer of baccalaureate aspirants beginning at community colleges. Based on data from the National Education Longitudinal Study of 1988 and the Postsecondary Education Transcript Study, a sequential logistic regression analysis was conducted to predict bachelor's degree-seeking community…

Kinetics of Aggregation with Choice

DOE PAGES

Ben-Naim, Eli; Krapivsky, Paul

2016-12-01

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

Remote sensing and airborne geophysics in the assessment of natural aggregate resources

USGS Publications Warehouse

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

1994-01-01

, and deposition of bedrock fragments. Consequently, most sand and gravel deposits are Tertiary or Quaternary in age and are most common in glaciated areas, alluvial basins, and along rivers and streams. The distribution of potential sources of natural aggregate in the United States is closely tied to physiography and the type of bedrock that occurs in an area. Using these criteria, the United States can be divided into 12 regions: western mountain ranges, alluvial basins, Columbia Plateau, Colorado Plateau and Wyoming basin, High Plains, nonglaciated central region, glaciated central region, Piedmont Blue Ridge region, glaciated northeastern and Superior uplands, Atlantic and Gulf coastal plain, Hawaiian Islands, and Alaska. Each region has similar types of natural aggregate sources within its boundary, although there may be wide variations in specific physical and chemical characteristics of the aggregates within a region. Conventional exploration for natural aggregate deposits has been largely a ground-based operation (field mapping, sampling, trenching and augering, resistivity), although aerial photos and topographic maps have been extensively used to target possible deposits for sampling and testing. Today, the exploration process also considers other factors such as the availability of the land, space and water supply for processing purposes, political and environmental factors, and distance from the market; exploration and planning cannot be separated. There are many physical properties and characteristics by which aggregate material is judged to be acceptable or unacceptable for specific applications; most of these properties and characteristics pertain only to individual aggregate particles and not to the bulk deposit. For example, properties of crushed stone aggregate particles such as thermal volume change, solubility, oxidation and hydration reactivity, and particle strength, among many others, are important consi

Bio-Inspired Aggregation Control of Carbon Nanotubes for Ultra-Strong Composites

PubMed Central

Han, Yue; Zhang, Xiaohua; Yu, Xueping; Zhao, Jingna; Li, Shan; Liu, Feng; Gao, Peng; Zhang, Yongyi; Zhao, Tong; Li, Qingwen

2015-01-01

High performance nanocomposites require well dispersion and high alignment of the nanometer-sized components, at a high mass or volume fraction as well. However, the road towards such composite structure is severely hindered due to the easy aggregation of these nanometer-sized components. Here we demonstrate a big step to approach the ideal composite structure for carbon nanotube (CNT) where all the CNTs were highly packed, aligned, and unaggregated, with the impregnated polymers acting as interfacial adhesions and mortars to build up the composite structure. The strategy was based on a bio-inspired aggregation control to limit the CNT aggregation to be sub 20–50 nm, a dimension determined by the CNT growth. After being stretched with full structural relaxation in a multi-step way, the CNT/polymer (bismaleimide) composite yielded super-high tensile strengths up to 6.27–6.94 GPa, more than 100% higher than those of carbon fiber/epoxy composites, and toughnesses up to 117–192 MPa. We anticipate that the present study can be generalized for developing multifunctional and smart nanocomposites where all the surfaces of nanometer-sized components can take part in shear transfer of mechanical, thermal, and electrical signals. PMID:26098627

Dynamics of proteins aggregation. II. Dynamic scaling in confined media

NASA Astrophysics Data System (ADS)

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

2018-03-01

In this paper, the second in a series devoted to molecular modeling of protein aggregation, a mesoscale model of proteins together with extensive discontinuous molecular dynamics simulation is used to study the phenomenon in a confined medium. The medium, as a model of a crowded cellular environment, is represented by a spherical cavity, as well as cylindrical tubes with two aspect ratios. The aggregation process leads to the formation of β sheets and eventually fibrils, whose deposition on biological tissues is believed to be a major factor contributing to many neuro-degenerative diseases, such as Alzheimer's, Parkinson's, and amyotrophic lateral sclerosis diseases. Several important properties of the aggregation process, including dynamic evolution of the total number of the aggregates, the mean aggregate size, and the number of peptides that contribute to the formation of the β sheets, have been computed. We show, similar to the unconfined media studied in Paper I [S. Zheng et al., J. Chem. Phys. 145, 134306 (2016)], that the computed properties follow dynamic scaling, characterized by power laws. The existence of such dynamic scaling in unconfined media was recently confirmed by experiments. The exponents that characterize the power-law dependence on time of the properties of the aggregation process in spherical cavities are shown to agree with those in unbounded fluids at the same protein density, while the exponents for aggregation in the cylindrical tubes exhibit sensitivity to the geometry of the system. The effects of the number of amino acids in the protein, as well as the size of the confined media, have also been studied. Similarities and differences between aggregation in confined and unconfined media are described, including the possibility of no fibril formation, if confinement is severe.

A Nuanced Look at Women in STEM Fields at Two-Year Colleges: Factors That Shape Female Students' Transfer Intent.

PubMed

Wang, Xueli; Chan, Hsun-Yu; Soffa, Sara Jimenez; Nachman, Brett Ranon

2017-01-01

In this study, we explored the relationship between the intent to transfer upward and a set of motivational, contextual, and socio-demographic background factors among 696 female students beginning in science, technology, engineering, and mathematics (STEM) programs or courses at two-year colleges in a Midwestern state. Drawing upon survey data and administrative records, our multinomial logistic regression analysis revealed that students' math and science self-efficacy beliefs, as well as transfer-oriented interaction, were significant and positive predictors for their intent to transfer into STEM fields as opposed to having no intent to transfer. In addition, the association between transfer intent and these key motivational and contextual factors was moderated by students' racial/ethnic backgrounds, marital status, and childcare obligations. For example, despite the positive relationship between transfer-oriented interaction and the intention to transfer into STEM fields, Black women were less likely to have intent to transfer into STEM fields than White students until Black students reported a moderate level of transfer-oriented interaction. Conversely, Hispanic students were more likely to report intent to transfer into STEM fields than their White peers, even when Hispanic students reported a relatively low level of engagement in transfer-oriented interaction. These and other reported findings bear important and nuanced implications as policymakers, educators, and researchers continue to discover ways to better support women's educational pathways and success in STEM fields at and through two-year colleges.

A Nuanced Look at Women in STEM Fields at Two-Year Colleges: Factors That Shape Female Students' Transfer Intent

PubMed Central

Wang, Xueli; Chan, Hsun-yu; Soffa, Sara Jimenez; Nachman, Brett Ranon

2017-01-01

In this study, we explored the relationship between the intent to transfer upward and a set of motivational, contextual, and socio-demographic background factors among 696 female students beginning in science, technology, engineering, and mathematics (STEM) programs or courses at two-year colleges in a Midwestern state. Drawing upon survey data and administrative records, our multinomial logistic regression analysis revealed that students' math and science self-efficacy beliefs, as well as transfer-oriented interaction, were significant and positive predictors for their intent to transfer into STEM fields as opposed to having no intent to transfer. In addition, the association between transfer intent and these key motivational and contextual factors was moderated by students' racial/ethnic backgrounds, marital status, and childcare obligations. For example, despite the positive relationship between transfer-oriented interaction and the intention to transfer into STEM fields, Black women were less likely to have intent to transfer into STEM fields than White students until Black students reported a moderate level of transfer-oriented interaction. Conversely, Hispanic students were more likely to report intent to transfer into STEM fields than their White peers, even when Hispanic students reported a relatively low level of engagement in transfer-oriented interaction. These and other reported findings bear important and nuanced implications as policymakers, educators, and researchers continue to discover ways to better support women's educational pathways and success in STEM fields at and through two-year colleges. PMID:28220102

Soil aggregation and aggregating agents as affected by long term contrasting management of an Anthrosol

NASA Astrophysics Data System (ADS)

Zhang, Shulan; Wang, Renjie; Yang, Xueyun; Sun, Benhua; Li, Qinghui

2016-12-01

Soil aggregation was studied in a 21-year experiment conducted on an Anthrosol. The soil management regimes consisted of cropland abandonment, bare fallow without vegetation and cropping system. The cropping system was combined with the following nutrient management treatments: control (CONTROL, no nutrient input); nitrogen, phosphorus and potassium (NPK); straw plus NPK (SNPK); and manure (M) plus NPK (MNPK). Compared with the CONTROL treatment, the abandonment treatment significantly increased the formation of large soil macroaggregates (>2 mm) and consequently improved the stability of aggregates in the surface soil layer due to enhancement of hyphal length and of soil organic matter content. However, in response to long-term bare fallow treatment aggregate stability was low, as were the levels of aggregating agents. Long term fertilization significantly redistributed macroaggregates; this could be mainly ascribed to soil organic matter contributing to the formation of 0.5-2 mm classes of aggregates and a decrease in the formation of the >2 mm class of aggregates, especially in the MNPK treatment. Overall, hyphae represented a major aggregating agent in both of the systems tested, while soil organic compounds played significantly different roles in stabilizing aggregates in Anthrosol when the cropping system and the soil management regimes were compared.

Soil aggregation and aggregating agents as affected by long term contrasting management of an Anthrosol

PubMed Central

Zhang, Shulan; Wang, Renjie; Yang, Xueyun; Sun, Benhua; Li, Qinghui

2016-01-01

Soil aggregation was studied in a 21-year experiment conducted on an Anthrosol. The soil management regimes consisted of cropland abandonment, bare fallow without vegetation and cropping system. The cropping system was combined with the following nutrient management treatments: control (CONTROL, no nutrient input); nitrogen, phosphorus and potassium (NPK); straw plus NPK (SNPK); and manure (M) plus NPK (MNPK). Compared with the CONTROL treatment, the abandonment treatment significantly increased the formation of large soil macroaggregates (>2 mm) and consequently improved the stability of aggregates in the surface soil layer due to enhancement of hyphal length and of soil organic matter content. However, in response to long-term bare fallow treatment aggregate stability was low, as were the levels of aggregating agents. Long term fertilization significantly redistributed macroaggregates; this could be mainly ascribed to soil organic matter contributing to the formation of 0.5–2 mm classes of aggregates and a decrease in the formation of the >2 mm class of aggregates, especially in the MNPK treatment. Overall, hyphae represented a major aggregating agent in both of the systems tested, while soil organic compounds played significantly different roles in stabilizing aggregates in Anthrosol when the cropping system and the soil management regimes were compared. PMID:27958366

Exciton interference revealed by energy dependent exciton transfer rate for ring-structured molecular systems.

PubMed

Yan, Yun-An

2016-01-14

The quantum interference is an intrinsic phenomenon in quantum physics for photon and massive quantum particles. In principle, the quantum interference may also occur with quasi-particles, such as the exciton. In this study, we show how the exciton quantum interference can be significant in aggregates through theoretical simulations with hierarchical equations of motion. The systems under investigation are generalized donor-bridge-acceptor model aggregates with the donor consisting of six homogeneous sites assuming the nearest neighbor coupling. For the models with single-path bridge, the exciton transfer time only shows a weak excitation energy dependence. But models with double-path bridge have a new short transfer time scale and the excitation energy dependence of the exciton transfer time assumes clear peak structure which is detectable with today's nonlinear spectroscopy. This abnormality is attributed to the exciton quantum interference and the condition for a clear observation in experiment is also explored.

From Dark to Light to Fluorescence Resonance Energy Transfer (FRET): Polarity-Sensitive Aggregation-Induced Emission (AIE)-Active Tetraphenylethene-Fused BODIPY Dyes with a Very Large Pseudo-Stokes Shift.

PubMed

Şen, Esra; Meral, Kadem; Atılgan, Serdar

2016-01-11

The work presented herein is devoted to the fabrication of large Stokes shift dyes in both organic and aqueous media by combining dark resonance energy transfer (DRET) and fluorescence resonance energy transfer (FRET) in one donor-acceptor system. In this respect, a series of donor-acceptor architectures of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes substituted by one, two, or three tetraphenylethene (TPE) luminogens were designed and synthesised. The photophysical properties of these three chromophore systems were studied to provide insight into the nature of donor-acceptor interactions in both THF and aqueous media. Because the generation of emissive TPE donor(s) is strongly polarity dependent, due to its aggregation-induced emission (AIE) feature, one might expect the formation of appreciable fluorescence emission intensity with a very large pseudo-Stokes shift in aqueous media when considering FRET process. Interestingly, similar results were also recorded in THF for the chromophore systems, although the TPE fragment(s) of the dyes are non-emissive. The explanation for this photophysical behaviour lies in the DRET. This is the first report on combining two energy-transfer processes, namely, FRET and DRET, in one polarity-sensitive donor-acceptor pair system. The accuracy of the dark-emissive donor property of the TPE luminogen is also presented for the first time as a new feature for AIE phenomena. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Distance-dependent energy transfer between indole and anthracene moieties in Langmuir Blodgett films

NASA Astrophysics Data System (ADS)

Saha, D. C.; Bhattacharjee, D.; Misra, T. N.

1998-09-01

1,2-Diphenyl indole (DPI) and 9,10-diphenyl anthracene (DPA) are non-amphiphilic molecules but form excellent LB films when mixed with stearic acid (SA). Spectroscopic investigations of these films indicate formation of aggregates of DPI and DPA in the mixed LB films. DPA has been used as the quencher of the fluorescence of the DPI donor. Distance-dependent energy transfer between donor and acceptor monolayers in the LB film, where they can be precisely separated by inert spacers of stearic acid layers of varied thickness, is shown to satisfy Khun's quadratic equation. This suggests that the donor excitations are delocalized. The large critical transfer distance estimated from the experimental results has been attributed to the formation of aggregates of the molecules in a LB monolayer.

A microfabricated platform to form three-dimensional toroidal multicellular aggregate.

PubMed

Masuda, Taisuke; Takei, Natsuki; Nakano, Takuma; Anada, Takahisa; Suzuki, Osamu; Arai, Fumihito

2012-12-01

Techniques that allow cells to self-assemble into three-dimensional (3D) spheroid microtissues provide powerful in vitro models that are becoming increasingly popular in fields such as stem cell research, tissue engineering, and cancer biology. Appropriate simulation of the 3D environment in which tissues normally develop and function is crucial for the engineering of in vitro models that can be used for the formation of complex tissues. We have developed a unique multicellular aggregate formation platform that utilizes a maskless gray-scale photolithography. The cellular aggregate formed using this platform has a toroidal-like geometry and includes a micro lumen that facilitates the supply of oxygen and growth factors and the expulsion of waste products. As a result, this platform was capable of rapidly producing hundreds of multicellular aggregates at a time, and of regulating the diameter of aggregates with complex design. These toroidal multicellular aggregates can grow as long-term culture. In addition, the micro lumen can be used as a continuous channel and for the insertion of a vascular system or a nerve system into the assembled tissue. These platform characteristics highlight its potential to be used in a wide variety of applications, e.g. as a bioactuator, as a micro-machine component or in drug screening and tissue engineering.

Molecular dynamics analysis of the aggregation propensity of polyglutamine segments

PubMed Central

Wen, Jingran; Scoles, Daniel R.

2017-01-01

Protein misfolding and aggregation is a pathogenic feature shared among at least ten polyglutamine (polyQ) neurodegenerative diseases. While solvent-solution interaction is a key factor driving protein folding and aggregation, the solvation properties of expanded polyQ tracts are not well understood. By using GPU-enabled all-atom molecular dynamics simulations of polyQ monomers in an explicit solvent environment, this study shows that solvent-polyQ interaction propensity decreases as the lengths of polyQ tract increases. This study finds a predominance in long-distance interactions between residues far apart in polyQ sequences with longer polyQ segments, that leads to significant conformational differences. This study also indicates that large loops, comprised of parallel β-structures, appear in long polyQ tracts and present new aggregation building blocks with aggregation driven by long-distance intra-polyQ interactions. Finally, consistent with previous observations using coarse-grain simulations, this study demonstrates that there is a gain in the aggregation propensity with increased polyQ length, and that this gain is correlated with decreasing ability of solvent-polyQ interaction. These results suggest the modulation of solvent-polyQ interactions as a possible therapeutic strategy for treating polyQ diseases. PMID:28542401

The critical success factors and impact of prior knowledge to nursing students when transferring nursing knowledge during nursing clinical practise.

PubMed

Tsai, Ming-Tien; Tsai, Ling-Long

2005-11-01

Nursing practise plays an important role in transferring nursing knowledge to nursing students. From the related literature review, prior knowledge will affect how learners gain new knowledge. There has been no direct examination of the prior knowledge interaction effect on students' performance and its influence on nursing students when evaluating the knowledge transfer success factors. This study explores (1) the critical success factors in transferring nursing knowledge, (2) the impact of prior knowledge when evaluating the success factors for transferring nursing knowledge. This research utilizes in-depth interviews to probe the initial success factor phase. A total of 422 valid questionnaires were conducted by the authors. The data were analysed by comparing the mean score and t-test between two groups. Seventeen critical success factors were identified by the two groups of students. Twelve items were selected to examine the diversity in the two groups. Students with prior knowledge were more independent than the other group. They also preferred self-directed learning over students without prior knowledge. Students who did not have prior knowledge were eager to take every opportunity to gain experience and more readily adopted new knowledge.

A study of the aggregation of cyclodextrins: Determination of the critical aggregation concentration, size of aggregates and thermodynamics using isodesmic and K2-K models.

PubMed

Do, Thao Thi; Van Hooghten, Rob; Van den Mooter, Guy

2017-04-15

The aggregation of three different cyclodextrins (CDs): 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), 2-hydroxypropyl-γ-cyclodextrin (HP-γ-CD) and sulfobutylether-β-cyclodextrin (SBE-β-CD) was studied. The critical aggregation concentration (cac) of these three CDs is quite similar and is situated at ca. 2% (m/v). There was only a small difference in the cac values determined by DLS and 1 H NMR. DLS measurements revealed that CDs in solution have three size populations wherein one of them is that of a single CD molecule. The size of aggregates determined by TEM appears to be similar to the size of the aggregates in the second size distribution determined by DLS. Isodesmic and K 2 -K self-assembly models were used for studying the aggregation process of HP-β-CD, HP-γ-CD and SBE-β-CD. The results showed that the aggregation process of these CDs is a cooperative one, where the first step of aggregation is less favorable than the next steps. The determined thermodynamic parameters showed that the aggregation process of all three CDs is spontaneous and exothermic and it is driven by an increase of the entropy of the environment. Copyright © 2017 Elsevier B.V. All rights reserved.

A Factorial Design Approach to Analyse the Effect of Coarse Recycled Concrete Aggregates on the Properties of Hot Mix Asphalt

NASA Astrophysics Data System (ADS)

Tanty, Kiranbala; Mukharjee, Bibhuti Bhusan; Das, Sudhanshu Shekhar

2018-06-01

The present study investigates the effect of replacement of coarse fraction of natural aggregates by recycled concrete aggregates on the properties of hot mix asphalt (HMA) using general factorial design approach. For this two factors i.e. recycled coarse aggregates percentage [RCA (%)] and bitumen content percentage [BC (%)] are considered. Tests have been carried out on the HMA type bituminous concrete, prepared with varying RCA (%) and BC (%). Analysis of variance has been performed on the experimental data to determine the effect of the chosen factors on various parameters such as stability, flow, air void, void mineral aggregate, void filled with bitumen and bulk density. The study depicts that RCA (%) and BC (%) have significant effect on the selected responses as p value is less than the chosen significance level. In addition to above, the outcomes of the statistical analysis indicate that interaction between factors have significant effects on void mineral aggregate and bulk density of bituminous concrete.

A Factorial Design Approach to Analyse the Effect of Coarse Recycled Concrete Aggregates on the Properties of Hot Mix Asphalt

NASA Astrophysics Data System (ADS)

Tanty, Kiranbala; Mukharjee, Bibhuti Bhusan; Das, Sudhanshu Shekhar

2018-02-01

The present study investigates the effect of replacement of coarse fraction of natural aggregates by recycled concrete aggregates on the properties of hot mix asphalt (HMA) using general factorial design approach. For this two factors i.e. recycled coarse aggregates percentage [RCA (%)] and bitumen content percentage [BC (%)] are considered. Tests have been carried out on the HMA type bituminous concrete, prepared with varying RCA (%) and BC (%). Analysis of variance has been performed on the experimental data to determine the effect of the chosen factors on various parameters such as stability, flow, air void, void mineral aggregate, void filled with bitumen and bulk density. The study depicts that RCA (%) and BC (%) have significant effect on the selected responses as p value is less than the chosen significance level. In addition to above, the outcomes of the statistical analysis indicate that interaction between factors have significant effects on void mineral aggregate and bulk density of bituminous concrete.

Lithologic characterization of active ITD aggregate sources and implications for aggregate quality.

DOT National Transportation Integrated Search

2014-03-01

Aggregate from 40 material sources across Idaho were sampled and the lithologies identified quantitatively. Aggregate compositions are compared with commercial AASHTO T 303 and ASTM C1293 results and the geologic map of Idaho to identify those rock t...

Aggregation and disaggregation kinetics of human blood platelets: Part II. Shear-induced platelet aggregation.

PubMed Central

Huang, P Y; Hellums, J D

1993-01-01

A population balance equation (PBE) mathematical model for analyzing platelet aggregation kinetics was developed in Part I (Huang, P. Y., and J. D. Hellums. 1993. Biophys. J. 65: 334-343) of a set of three papers. In this paper, Part II, platelet aggregation and related reactions are studied in the uniform, known shear stress field of a rotational viscometer, and interpreted by means of the model. Experimental determinations are made of the platelet-aggregate particle size distributions as they evolve in time under the aggregating influence of shear stress. The PBE model is shown to give good agreement with experimental determinations when either a reversible (aggregation and disaggregation) or an irreversible (no disaggregation) form of the model is used. This finding suggests that for the experimental conditions studied disaggregation processes are of only secondary importance. During shear-induced platelet aggregation, only a small fraction of platelet collisions result in the binding together of the involved platelets. The modified collision efficiency is approximately zero for shear rates below 3000 s-1. It increases with shear rates above 3000 s-1 to about 0.01 for a shear rate of 8000 s-1. Addition of platelet chemical agonists yields order of magnitude increases in collision efficiency. The collision efficiency for shear-induced platelet aggregation is about an order of magnitude less at 37 degrees C than at 24 degrees C. The PBE model gives a much more accurate representation of aggregation kinetics than an earlier model based on a monodispersed particle size distribution. PMID:8369442

Vertical migration of aggregated aerobic and anaerobic ammonium oxidizers enhances oxygen uptake in a stagnant water layer.

PubMed

Vlaeminck, Siegfried E; Dierick, Katleen; Boon, Nico; Verstraete, Willy

2007-07-01

Ammonium can be removed as dinitrogen gas by cooperating aerobic and anaerobic ammonium-oxidizing bacteria (AerAOB and AnAOB). The goal of this study was to verify putative mutual benefits for aggregated AerAOB and AnAOB in a stagnant freshwater environment. In an ammonium fed water column, the biological oxygen consumption rate was, on average, 76 kg O(2) ha(-1) day(-1). As the oxygen transfer rate of an abiotic control column was only 17 kg O(2) ha(-1) day(-1), biomass activity enhanced the oxygen transfer. Increasing the AnAOB gas production increased the oxygen consumption rate with more than 50% as a result of enhanced vertical movement of the biomass. The coupled decrease in dissolved oxygen concentration increased the diffusional oxygen transfer from the atmosphere in the water. Physically preventing the biomass from rising to the upper water layer instantaneously decreased oxygen and ammonium consumption and even led to the occurrence of some sulfate reduction. Floating of the biomass was further confirmed to be beneficial, as this allowed for the development of a higher AerAOB and AnAOB activity, compared to settled biomass. Overall, the results support mutual benefits for aggregated AerAOB and AnAOB, derived from the biomass uplifting effect of AnAOB gas production.

Model for amorphous aggregation processes

NASA Astrophysics Data System (ADS)

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

2009-11-01

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

Theoretical deposition of carcinogenic particle aggregates in the upper respiratory tract.

PubMed

Sturm, Robert

2013-10-01

Numerous particles suspended in the atmosphere are composed of smaller particular components that form aggregates with highly irregular shape. Such aggregates, among which dusts and soot are the most prominent examples, may be taken up into the respiratory tract and, in the worst case, initiate a malignant transformation of lung cells. Particle aggregates were theoretically modelled by using small spheres with equal diameters (1 nm) and arranging them randomly. This procedure resulted in the generation of various aggregate shapes (chain-like, loose, compact), for which essential parameters such as dynamic shape factors, χ, and aerodynamic diameters, dae , were computed. Deposition of aggregates consisting of 10, 50, 100, and 1,000 nano-spheres was simulated for the uppermost parts of the human respiratory system (extrathoracic region and airway generation 0 to 4), thereby distinguishing between sitting and light-work breathing as well as between nasal and oral inhalation. Based upon the modelling results, aggregate deposition in the human respiratory system can be described as a function of (I) aerodynamic diameter; (II) inhaled particle position within the airway system; and (III) breathing conditions. Therefore, highest deposition values were obtained for nano-scale aggregates (<10 nm), whereas larger aggregates exhibited slightly to significantly reduced deposition probabilities. Extrathoracic regions and uppermost bronchi (generations 0 to 1) were marked by most effective particle capture. Any increase of inhaled air volumes and reduction of breathing times resulted in an enhancement of deposition probabilities of larger particles. Based on the results derived from this study it may be concluded that small particle aggregates are accumulated in the uppermost compartments of the human respiratory tract, where they may unfold their unwholesome potential. In the case of carcinogenic particles being stored in epithelial cells for a longer time span, malignant

Dynamics of protein aggregation and oligomer formation governed by secondary nucleation

NASA Astrophysics Data System (ADS)

Michaels, Thomas C. T.; Lazell, Hamish W.; Arosio, Paolo; Knowles, Tuomas P. J.

2015-08-01

The formation of aggregates in many protein systems can be significantly accelerated by secondary nucleation, a process where existing assemblies catalyse the nucleation of new species. In particular, secondary nucleation has emerged as a central process controlling the proliferation of many filamentous protein structures, including molecular species related to diseases such as sickle cell anemia and a range of neurodegenerative conditions. Increasing evidence suggests that the physical size of protein filaments plays a key role in determining their potential for deleterious interactions with living cells, with smaller aggregates of misfolded proteins, oligomers, being particularly toxic. It is thus crucial to progress towards an understanding of the factors that control the sizes of protein aggregates. However, the influence of secondary nucleation on the time evolution of aggregate size distributions has been challenging to quantify. This difficulty originates in large part from the fact that secondary nucleation couples the dynamics of species distant in size space. Here, we approach this problem by presenting an analytical treatment of the master equation describing the growth kinetics of linear protein structures proliferating through secondary nucleation and provide closed-form expressions for the temporal evolution of the resulting aggregate size distribution. We show how the availability of analytical solutions for the full filament distribution allows us to identify the key physical parameters that control the sizes of growing protein filaments. Furthermore, we use these results to probe the dynamics of the populations of small oligomeric species as they are formed through secondary nucleation and discuss the implications of our work for understanding the factors that promote or curtail the production of these species with a potentially high deleterious biological activity.

Dynamics of protein aggregation and oligomer formation governed by secondary nucleation

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

Michaels, Thomas C. T., E-mail: tctm3@cam.ac.uk; Lazell, Hamish W.; Arosio, Paolo

2015-08-07

The formation of aggregates in many protein systems can be significantly accelerated by secondary nucleation, a process where existing assemblies catalyse the nucleation of new species. In particular, secondary nucleation has emerged as a central process controlling the proliferation of many filamentous protein structures, including molecular species related to diseases such as sickle cell anemia and a range of neurodegenerative conditions. Increasing evidence suggests that the physical size of protein filaments plays a key role in determining their potential for deleterious interactions with living cells, with smaller aggregates of misfolded proteins, oligomers, being particularly toxic. It is thus crucial tomore » progress towards an understanding of the factors that control the sizes of protein aggregates. However, the influence of secondary nucleation on the time evolution of aggregate size distributions has been challenging to quantify. This difficulty originates in large part from the fact that secondary nucleation couples the dynamics of species distant in size space. Here, we approach this problem by presenting an analytical treatment of the master equation describing the growth kinetics of linear protein structures proliferating through secondary nucleation and provide closed-form expressions for the temporal evolution of the resulting aggregate size distribution. We show how the availability of analytical solutions for the full filament distribution allows us to identify the key physical parameters that control the sizes of growing protein filaments. Furthermore, we use these results to probe the dynamics of the populations of small oligomeric species as they are formed through secondary nucleation and discuss the implications of our work for understanding the factors that promote or curtail the production of these species with a potentially high deleterious biological activity.« less

Heating of Porous Icy Dust Aggregates

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

Sirono, Sin-iti

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

Inhibition of cyclooxygenase-independent platelet aggregation by sodium salicylate.

PubMed

Violi, F; Alessandri, C; Praticò, D; Guzzo, A; Ghiselli, A; Balsano, F

1989-06-15

The effect of acetylsalicylic acid (ASA) on platelet aggregation (PA) and thromboxane A2 (TxA2) formation was investigated in vitro and ex vivo after 1 g or 300 mg ASA administration to healthy subjects. 50-100 microM ASA inhibited PA by single aggregating agent such as platelet aggregating factor (PAF) or epinephrine and reduced to less than or equal to 5% of control platelet TxB2 formation, but did not influence PA by epinephrine plus PAF. The latter was inhibited by increasing ASA concentration. In samples incubated with 100 microM ASA and stimulated with epinephrine plus PAF, PA could be inhibited by the addition of 100-300 microM sodium salicylate. After 300 mg-1 g ASA administration to healthy subjects, the inhibition of PA by epinephrine plus PAF was more marked by highest doses of ASA. This study suggests that aspirin inhibits PA with a cyclooxygenase-independent mechanism; this effect is mediated, at least in vitro, by salicylic acid.

Factor IX expression in skeletal muscle of a severe hemophilia B patient 10 years after AAV-mediated gene transfer.

PubMed

Buchlis, George; Podsakoff, Gregory M; Radu, Antonetta; Hawk, Sarah M; Flake, Alan W; Mingozzi, Federico; High, Katherine A

2012-03-29

In previous work we transferred a human factor IX-encoding adeno-associated viral vector (AAV) into skeletal muscle of men with severe hemophilia B. Biopsy of injected muscle up to 1 year after vector injection showed evidence of gene transfer by Southern blot and of protein expression by IHC and immunofluorescent staining. Although the procedure appeared safe, circulating F.IX levels remained subtherapeutic (< 1%). Recently, we obtained muscle tissue from a subject injected 10 years earlier who died of causes unrelated to gene transfer. Using Western blot, IHC, and immunofluorescent staining, we show persistent factor IX expression in injected muscle tissue. F.IX transcripts were detected in injected skeletal muscle using RT-PCR, and isolated whole genomic DNA tested positive for the presence of the transferred AAV vector sequence. This is the longest reported transgene expression to date from a parenterally administered AAV vector, with broad implications for the future of muscle-directed gene transfer.

Factor IX expression in skeletal muscle of a severe hemophilia B patient 10 years after AAV-mediated gene transfer

PubMed Central

Buchlis, George; Podsakoff, Gregory M.; Radu, Antonetta; Hawk, Sarah M.; Flake, Alan W.; Mingozzi, Federico

2012-01-01

In previous work we transferred a human factor IX–encoding adeno-associated viral vector (AAV) into skeletal muscle of men with severe hemophilia B. Biopsy of injected muscle up to 1 year after vector injection showed evidence of gene transfer by Southern blot and of protein expression by IHC and immunofluorescent staining. Although the procedure appeared safe, circulating F.IX levels remained subtherapeutic (< 1%). Recently, we obtained muscle tissue from a subject injected 10 years earlier who died of causes unrelated to gene transfer. Using Western blot, IHC, and immunofluorescent staining, we show persistent factor IX expression in injected muscle tissue. F.IX transcripts were detected in injected skeletal muscle using RT-PCR, and isolated whole genomic DNA tested positive for the presence of the transferred AAV vector sequence. This is the longest reported transgene expression to date from a parenterally administered AAV vector, with broad implications for the future of muscle-directed gene transfer. PMID:22271447

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.

Protein aggregation and prionopathies.

PubMed

Renner, M; Melki, R

2014-06-01

Prion protein and prion-like proteins share a number of characteristics. From the molecular point of view, they are constitutive proteins that aggregate following conformational changes into insoluble particles. These particles escape the cellular clearance machinery and amplify by recruiting the soluble for of their constituting proteins. The resulting protein aggregates are responsible for a number of neurodegenerative diseases such as Creutzfeldt-Jacob, Alzheimer, Parkinson and Huntington diseases. In addition, there are increasing evidences supporting the inter-cellular trafficking of these aggregates, meaning that they are "transmissible" between cells. There are also evidences that brain homogenates from individuals developing Alzheimer and Parkinson diseases propagate the disease in recipient model animals in a manner similar to brain extracts of patients developing Creutzfeldt-Jacob's disease. Thus, the propagation of protein aggregates from cell to cell may be a generic phenomenon that contributes to the evolution of neurodegenerative diseases, which has important consequences on human health issues. Moreover, although the distribution of protein aggregates is characteristic for each disease, new evidences indicate the possibility of overlaps and crosstalk between the different disorders. Despite the increasing evidences that support prion or prion-like propagation of protein aggregates, there are many unanswered questions regarding the mechanisms of toxicity and this is a field of intensive research nowadays. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Factors, Practices, and Policies Influencing Students' Upward Transfer to Baccalaureate-Degree Programs and Institutions: A Mixed Methods Analysis

ERIC Educational Resources Information Center

LaSota, Robin Rae

2013-01-01

My dissertation utilizes an explanatory, sequential mixed-methods research design to assess factors influencing community college students' transfer probability to baccalaureate-granting institutions and to present promising practices in colleges and states directed at improving upward transfer, particularly for low-income and first-generation…

Platelet factor XIIIa release during platelet aggregation and plasma clot strength measured by thrombelastography in patients with coronary artery disease treated with clopidogrel.

PubMed

Kreutz, Rolf P; Owens, Janelle; Lu, Deshun; Nystrom, Perry; Jin, Yan; Kreutz, Yvonne; Desta, Zeruesenay; Flockhart, David A

2015-01-01

It has been estimated that up to half of circulating factor XIIIa (FXIIIa) is stored in platelets. The release of FXIIIa from platelets upon stimulation with adenosine diphosphate (ADP) in patients with coronary artery disease treated with dual antiplatelet therapy has not been previously examined. Samples from 96 patients with established coronary artery disease treated with aspirin and clopidogrel were examined. Platelet aggregation was performed by light transmittance aggregometry in platelet-rich plasma (PRP), with platelet-poor plasma (PPP) as reference, and ADP 5 µM as agonist. Kaolin-activated thrombelastography (TEG) was performed in citrate PPP. PRP after aggregation was centrifuged and plasma supernatant (PSN) collected. FXIIIa was measured in PPP and PSN. Platelet aggregation after stimulation with ADP 5 µM resulted in 24% additional FXIIIa release in PSN as compared to PPP (99.3 ± 27 vs. 80.3 ± 24%, p < 0.0001). FXIIIa concentration in PSN correlated with maximal plasma clot strength (TEG-G) (r = 0.48, p < 0.0001), but not in PPP (r = 0.15, p = 0.14). Increasing quartiles of platelet-derived FXIIIa were associated with incrementally higher TEG-G (p = 0.012). FXIIIa release was similar between clopidogrel responders and non-responders (p = 0.18). In summary, platelets treated with aspirin and clopidogrel release a significant amount of FXIIIa upon aggregation by ADP. Platelet-derived FXIIIa may contribute to differences in plasma TEG-G, and thus, in part, provide a mechanistic explanation for high clot strength observed as a consequence of platelet activation. Variability in clopidogrel response does not significantly influence FXIIIa release from platelets.

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

Examining the Factor Structure and Predictive Ability of the German-Version of the Learning Transfer Systems Inventory

ERIC Educational Resources Information Center

Bates, Reid; Kauffeld, Simone; Holton, Elwood F., III

2007-01-01

Purpose: The purpose of this research is to examine the construct and predictive ability of a German version of the Learning Transfer Systems Inventory (GLTSI), an instrument designed to assess a constellation of 16 factors known to influence the transfer of training in work settings. Design/methodology/approach: The survey data for this study was…

An exploration of the perceived factors that affect the learning and transfer of skills taught to student midwives.

PubMed

Longworth, Mary K

2013-08-01

the aim of this study was to examine the attitudes of student midwives towards skills training and practise. The objectives were to explore the factors in the skills laboratory environment and in clinical practice which affect how successfully student midwives transfer into clinical practice the various skills they have learnt in preparation for an Objective Structured Clinical Examination. a review of the background literature revealed that there were many variables related to successful transfer of skills in general but there appeared to be a gap around perceived factors affecting transfer of skills of student midwives. a mixed methods design was conducted using both questionnaires and semi-structured interviews between June and August 2010. questionnaires were administered to all midwifery students at one university in Wales. These were later followed by semi-structured interviews for 6 student midwives who were purposively selected from all year groups. the results from the questionnaires revealed that a majority of students had positive attitudes to educators and mentors and to their skills acquisition experience in the skills laboratory and to the available opportunities to practise in clinical practice. Although students believed in the transferability of skills from the laboratory setting to clinical practice, a majority thought that clinical practice provided them with a better opportunity to learn clinical skills. The semi-structured interviews demonstrated that facilitating factors in the skills laboratory included having adequate instruction as well as having a designated space. Hindering factors included unrealistic models and equipment. In clinical practice, facilitating factors included having the opportunities to practise skills and support and feedback from the mentor. Hindering factors included deficits in the student-mentor relationship. this study highlighted that midwifery students must be adequately prepared to carry out clinical skills

Local convective heat transfer coefficient and friction factor of CuO/water nanofluid in a microchannel heat sink

NASA Astrophysics Data System (ADS)

Chabi, A. R.; Zarrinabadi, S.; Peyghambarzadeh, S. M.; Hashemabadi, S. H.; Salimi, M.

2017-02-01

Forced convective heat transfer in a microchannel heat sink (MCHS) using CuO/water nanofluids with 0.1 and 0.2 vol% as coolant was investigated. The experiments were focused on the heat transfer enhancement in the channel entrance region at Re < 1800. Hydraulic performance of the MCHS was also estimated by measuring friction factor and pressure drop. Results showed that higher convective heat transfer coefficient was obtained at the microchannel entrance. Maximum enhancement of the average heat transfer coefficient compared with deionized water was about 40 % for 0.2 vol% nanofluid at Re = 1150. Enhancement of the convective heat transfer coefficient of nanofluid decreased with further increasing of Reynolds number.

Network Intrusion Detection and Visualization using Aggregations in a Cyber Security Data Warehouse

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

Czejdo, Bogdan; Ferragut, Erik M; Goodall, John R

2012-01-01

The challenge of achieving situational understanding is a limiting factor in effective, timely, and adaptive cyber-security analysis. Anomaly detection fills a critical role in network assessment and trend analysis, both of which underlie the establishment of comprehensive situational understanding. To that end, we propose a cyber security data warehouse implemented as a hierarchical graph of aggregations that captures anomalies at multiple scales. Each node of our pro-posed graph is a summarization table of cyber event aggregations, and the edges are aggregation operators. The cyber security data warehouse enables domain experts to quickly traverse a multi-scale aggregation space systematically. We describemore » the architecture of a test bed system and a summary of results on the IEEE VAST 2012 Cyber Forensics data.« less

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

Evidence for TiO2 nanoparticle transfer in a hard-rock aquifer.

PubMed

Cary, Lise; Pauwels, Hélène; Ollivier, Patrick; Picot, Géraldine; Leroy, Philippe; Mougin, Bruno; Braibant, Gilles; Labille, Jérôme

2015-08-01

Water flow and TiO2 nanoparticle (NP) transfer in a fractured hard-rock aquifer were studied in a tracer test experiment at a pilot site in Brittany, France. Results from the Br tracer test show that the schist aquifer can be represented by a two-layer medium comprising i) fractures with low longitudinal dispersivity in which water and solute transport is relatively fast, and ii) a network of small fissures with high longitudinal dispersivity in which transport is slower. Although a large amount of NPs was retained within the aquifer, a significant TiO2 concentration was measured in a well 15m downstream of the NP injection well, clearly confirming the potential for TiO2 NPs to be transported in groundwater. The Ti concentration profile in the downstream well was modelled using a two-layer medium approach. The delay used for the TiO2 NPs simulation compared to the Br concentration profiles in the downstream well indicate that the aggregated TiO2 NPs interacted with the rock. Unlike Br, NPs do not penetrate the entire pore network during transfer because of electrostatic interactions between NP aggregates and the rock and also to the aggregate size and the hydrodynamic conditions, especially where the porosity is very low; NPs with a weak negative charge can be attached onto the rock surface, and more particularly onto the positively charged iron oxyhydroxides coating the main pathways due to natural denitrification. Nevertheless, TiO2 NPs are mobile and transfer within fracture and fissure media. Any modification of the aquifer's chemical conditions is likely to impact the groundwater pH and, the nitrate content and the denitrification process, and thus affect NP aggregation and attachment. Copyright © 2015 Elsevier B.V. All rights reserved.

Inhibition of GNNQQNY prion peptide aggregation by trehalose: a mechanistic view.

PubMed

Katyal, Nidhi; Deep, Shashank

2017-07-26

Deposition of amyloid fibrils is the seminal event in the pathogenesis of numerous neurodegenerative diseases. The formation of this amyloid assembly is the manifestation of a cascade of structural transitions including toxic oligomer formation in the early stages of aggregation. Thus a viable therapeutic strategy involves the use of small molecular ligands to interfere with this assembly. In this perspective, we have explored the kinetics of aggregate formation of the fibril forming GNNQQNY peptide fragment from the yeast prion protein SUP35 using multiple all atom MD simulations with explicit solvent and provided mechanistic insights into the way trehalose, an experimentally known aggregation inhibitor, modulates the aggregation pathway. The results suggest that the assimilation process is impeded by different barriers at smaller and larger oligomeric sizes: the initial one being easily surpassed at higher temperatures and peptide concentrations. The kinetic profile demonstrates that trehalose delays the aggregation process by increasing both these activation barriers, specifically the latter one. It increases the sampling of small-sized aggregates that lack the beta sheet conformation. Analysis reveals that the barrier in the growth of larger stable oligomers causes the formation of multiple stable small oligomers which then fuse together bimolecularly. The PCA of 26 properties was carried out to deconvolute the events within the temporary lag phases, which suggested dynamism in lags involving an increase in interchain contacts and burial of SASA. The predominant growth route is monomer addition, which changes to condensation on account of a large number of depolymerisation events in the presence of trehalose. The favourable interaction of trehalose specifically with the sidechain of the peptide promotes crowding of trehalose molecules in its vicinity - the combination of both these factors imparts the observed behaviour. Furthermore, increasing trehalose

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

NASA Astrophysics Data System (ADS)

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

2009-06-01

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

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…

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

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

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

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

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.

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

USGS Publications Warehouse

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

2004-01-01

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

Exciton interference revealed by energy dependent exciton transfer rate for ring-structured molecular systems

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

Yan, Yun-An, E-mail: yunan@gznc.edu.cn

2016-01-14

The quantum interference is an intrinsic phenomenon in quantum physics for photon and massive quantum particles. In principle, the quantum interference may also occur with quasi-particles, such as the exciton. In this study, we show how the exciton quantum interference can be significant in aggregates through theoretical simulations with hierarchical equations of motion. The systems under investigation are generalized donor-bridge-acceptor model aggregates with the donor consisting of six homogeneous sites assuming the nearest neighbor coupling. For the models with single-path bridge, the exciton transfer time only shows a weak excitation energy dependence. But models with double-path bridge have a newmore » short transfer time scale and the excitation energy dependence of the exciton transfer time assumes clear peak structure which is detectable with today’s nonlinear spectroscopy. This abnormality is attributed to the exciton quantum interference and the condition for a clear observation in experiment is also explored.« less

A study of estrogen metabolic clearance rates and transfer factors

PubMed Central

Hembree, W. C.; Bardin, C. W.; Lipsett, M. B.

1969-01-01

We have attempted to measure the metabolic clearance rates (MCR) and the transfer factors of estradiol (E2) and estrone (E1) during 2-hr and 12-hr infusions. When estradiol-3H was infused for 2 hr, apparent equilibrium was reached at 70 min; the 12-hr infusions showed that plasma estradiol-3H levels increased slowly throughout the infusion. When estrone-3H was infused, constancy of estrone-3H levels was not attained in either the 2-hr infusions or in the two 12-hr infusions. The tritium level in the metabolite of the infused estrogen did not become constant in 50% of the short infusions and increased during all the long infusions. Thus, the conversion ratios CE1E2 and CE2E1 continually changed and transfer factors could not be calculated. The apparent “MCR'S” calculated on the basis of the 2-hr studies expressed as liters/24 hr per m2 ±SD were: “MCRE1” (women) 980 ±94, (men) 1170 ±95; “MCRE2” (women) 615 ±17, (men) 830 ±30. The estradiol “MCR's” differed significantly between men and women. “MCRE2” was the same using either estradiol-14C or -3H and was unchanged by the infusion of 170 μg of estradiol daily. Postmenopausal women had estrogen “MCR's” in the same range as premenopausal women. Excess glucocorticoids increased the “MCRE2.” PMID:5822587

Modelling oxygen transfer using dynamic alpha factors.

PubMed

Jiang, Lu-Man; Garrido-Baserba, Manel; Nolasco, Daniel; Al-Omari, Ahmed; DeClippeleir, Haydee; Murthy, Sudhir; Rosso, Diego

2017-11-01

Due to the importance of wastewater aeration in meeting treatment requirements and due to its elevated energy intensity, it is important to describe the real nature of an aeration system to improve design and specification, performance prediction, energy consumption, and process sustainability. Because organic loadings drive aeration efficiency to its lowest value when the oxygen demand (energy) is the highest, the implications of considering their dynamic nature on energy costs are of utmost importance. A dynamic model aimed at identifying conservation opportunities is presented. The model developed describes the correlation between the COD concentration and the α factor in activated sludge. Using the proposed model, the aeration efficiency is calculated as a function of the organic loading (i.e. COD). This results in predictions of oxygen transfer values that are more realistic than the traditional method of assuming constant α values. The model was applied to two water resource recovery facilities, and was calibrated and validated with time-sensitive databases. Our improved aeration model structure increases the quality of prediction of field data through the recognition of the dynamic nature of the alpha factor (α) as a function of the applied oxygen demand. For the cases presented herein, the model prediction of airflow improved by 20-35% when dynamic α is used. The proposed model offers a quantitative tool for the prediction of energy demand and for minimizing aeration design uncertainty. Copyright © 2017 Elsevier Ltd. All rights reserved.

Holographic Characterization of Colloidal Fractal Aggregates

NASA Astrophysics Data System (ADS)

Wang, Chen; Cheong, Fook Chiong; Ruffner, David B.; Zhong, Xiao; Ward, Michael D.; Grier, David G.

In-line holographic microscopy images of micrometer-scale fractal aggregates can be interpreted with the Lorenz-Mie theory of light scattering and an effective-sphere model to obtain each aggregate's size and the population-averaged fractal dimension. We demonstrate this technique experimentally using model fractal clusters of polystyrene nanoparticles and fractal protein aggregates composed of bovine serum albumin and bovine pancreas insulin. This technique can characterize several thousand aggregates in ten minutes and naturally distinguishes aggregates from contaminants such as silicone oil droplets. Work supported by the SBIR program of the NSF.

Formation and structure of stable aggregates in binary diffusion-limited cluster-cluster aggregation processes

NASA Astrophysics Data System (ADS)

López-López, J. M.; Moncho-Jordá, A.; Schmitt, A.; Hidalgo-Álvarez, R.

2005-09-01

Binary diffusion-limited cluster-cluster aggregation processes are studied as a function of the relative concentration of the two species. Both, short and long time behaviors are investigated by means of three-dimensional off-lattice Brownian Dynamics simulations. At short aggregation times, the validity of the Hogg-Healy-Fuerstenau approximation is shown. At long times, a single large cluster containing all initial particles is found to be formed when the relative concentration of the minority particles lies above a critical value. Below that value, stable aggregates remain in the system. These stable aggregates are composed by a few minority particles that are highly covered by majority ones. Our off-lattice simulations reveal a value of approximately 0.15 for the critical relative concentration. A qualitative explanation scheme for the formation and growth of the stable aggregates is developed. The simulations also explain the phenomenon of monomer discrimination that was observed recently in single cluster light scattering experiments.

Observing Convective Aggregation

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

Generation of urban road dust from anti-skid and asphalt concrete aggregates.

PubMed

Tervahattu, Heikki; Kupiainen, Kaarle J; Räisänen, Mika; Mäkelä, Timo; Hillamo, Risto

2006-04-30

Road dust forms an important component of airborne particulate matter in urban areas. In many winter cities the use of anti-skid aggregates and studded tires enhance the generation of mineral particles. The abrasion particles dominate the PM10 during springtime when the material deposited in snow is resuspended. This paper summarizes the results from three test series performed in a test facility to assess the factors that affect the generation of abrasion components of road dust. Concentrations, mass size distribution and composition of the particles were studied. Over 90% of the particles were aluminosilicates from either anti-skid or asphalt concrete aggregates. Mineral particles were observed mainly in the PM10 fraction, the fine fraction being 12% and submicron size being 6% of PM10 mass. The PM10 concentrations increased as a function of the amount of anti-skid aggregate dispersed. The use of anti-skid aggregate increased substantially the amount of PM10 originated from the asphalt concrete. It was concluded that anti-skid aggregate grains contribute to pavement wear. The particle size distribution of the anti-skid aggregates had great impact on PM10 emissions which were additionally enhanced by studded tires, modal composition, and texture of anti-skid aggregates. The results emphasize the interaction of tires, anti-skid aggregate, and asphalt concrete pavement in the production of dust emissions. They all must be taken into account when measures to reduce road dust are considered. The winter maintenance and springtime cleaning must be performed properly with methods which are efficient in reducing PM10 dust.

Constructing Nucleon Operators on a Lattice for Form Factors with High Momentum Transfer

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

Syritsyn, Sergey; Gambhir, Arjun S.; Musch, Bernhard U.

We present preliminary results of computing nucleon form factor at high momentum transfer using the 'boosted' or 'momentum' smearing. We use gauge configurations generated with N f = 2 + 1dynamical Wilson-clover fermions and study the connected as well as disconnected contributions to the nucleon form factors. Our initial results indicate that boosted smearing helps to improve the signal for nucleon correlators at high momentum. However, we also find evidence for large excited state contributions, which will likely require variational analysis to isolate the boosted nucleon ground state.

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.

Lightweight aggregate abrasion study.

DOT National Transportation Integrated Search

1963-02-01

The rapid increase in the use of lightweight aggregates in structural concrete has created a number of problems for the Materials Engineer in evaluating this type aggregate. Exhaustive studies are being made of a number of properties of lightweight a...

A novel weight determination method for time series data aggregation

NASA Astrophysics Data System (ADS)

Xu, Paiheng; Zhang, Rong; Deng, Yong

2017-09-01

Aggregation in time series is of great importance in time series smoothing, predicting and other time series analysis process, which makes it crucial to address the weights in times series correctly and reasonably. In this paper, a novel method to obtain the weights in time series is proposed, in which we adopt induced ordered weighted aggregation (IOWA) operator and visibility graph averaging (VGA) operator and linearly combine the weights separately generated by the two operator. The IOWA operator is introduced to the weight determination of time series, through which the time decay factor is taken into consideration. The VGA operator is able to generate weights with respect to the degree distribution in the visibility graph constructed from the corresponding time series, which reflects the relative importance of vertices in time series. The proposed method is applied to two practical datasets to illustrate its merits. The aggregation of Construction Cost Index (CCI) demonstrates the ability of proposed method to smooth time series, while the aggregation of The Taiwan Stock Exchange Capitalization Weighted Stock Index (TAIEX) illustrate how proposed method maintain the variation tendency of original data.

Using bacterial inclusion bodies to screen for amyloid aggregation inhibitors.

PubMed

Villar-Piqué, Anna; Espargaró, Alba; Sabaté, Raimon; de Groot, Natalia S; Ventura, Salvador

2012-05-03

The amyloid-β peptide (Aβ42) is the main component of the inter-neuronal amyloid plaques characteristic of Alzheimer's disease (AD). The mechanism by which Aβ42 and other amyloid peptides assemble into insoluble neurotoxic deposits is still not completely understood and multiple factors have been reported to trigger their formation. In particular, the presence of endogenous metal ions has been linked to the pathogenesis of AD and other neurodegenerative disorders. Here we describe a rapid and high-throughput screening method to identify molecules able to modulate amyloid aggregation. The approach exploits the inclusion bodies (IBs) formed by Aβ42 when expressed in bacteria. We have shown previously that these aggregates retain amyloid structural and functional properties. In the present work, we demonstrate that their in vitro refolding is selectively sensitive to the presence of aggregation-promoting metal ions, allowing the detection of inhibitors of metal-promoted amyloid aggregation with potential therapeutic interest. Because IBs can be produced at high levels and easily purified, the method overcomes one of the main limitations in screens to detect amyloid modulators: the use of expensive and usually highly insoluble synthetic peptides.

Water-Transfer Slows Aging in Saccharomyces cerevisiae

PubMed Central

Cohen, Aviv; Weindling, Esther; Rabinovich, Efrat; Nachman, Iftach; Fuchs, Shai; Chuartzman, Silvia; Gal, Lihi; Schuldiner, Maya; Bar-Nun, Shoshana

2016-01-01

Transferring Saccharomyces cerevisiae cells to water is known to extend their lifespan. However, it is unclear whether this lifespan extension is due to slowing the aging process or merely keeping old yeast alive. Here we show that in water-transferred yeast, the toxicity of polyQ proteins is decreased and the aging biomarker 47Q aggregates at a reduced rate and to a lesser extent. These beneficial effects of water-transfer could not be reproduced by diluting the growth medium and depended on de novo protein synthesis and proteasomes levels. Interestingly, we found that upon water-transfer 27 proteins are downregulated, 4 proteins are upregulated and 81 proteins change their intracellular localization, hinting at an active genetic program enabling the lifespan extension. Furthermore, the aging-related deterioration of the heat shock response (HSR), the unfolded protein response (UPR) and the endoplasmic reticulum-associated protein degradation (ERAD), was largely prevented in water-transferred yeast, as the activities of these proteostatic network pathways remained nearly as robust as in young yeast. The characteristics of young yeast that are actively maintained upon water-transfer indicate that the extended lifespan is the outcome of slowing the rate of the aging process. PMID:26862897

Curcumin inhibits aggregation of alpha-synuclein.

PubMed

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

2008-04-01

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

Evaluation and testing of a lightweight fine aggregate concrete bridge deck in Buchanan County, Iowa : tech transfer summaries.

DOT National Transportation Integrated Search

2016-05-01

Using saturated lightweight fine aggregate (LWFA) in concrete mixtures : can replenish water that is depleted during cement hydration without : influencing the water-to-cement (w/c) ratio. This process, known as : internal curing (IC), can contribute...

Different Factors Affecting Human ANP Amyloid Aggregation and Their Implications in Congestive Heart Failure

PubMed Central

Millucci, Lia; Paccagnini, Eugenio; Ghezzi, Lorenzo; Bernardini, Giulia; Braconi, Daniela; Laschi, Marcella; Consumi, Marco; Spreafico, Adriano; Tanganelli, Piero; Lupetti, Pietro; Magnani, Agnese; Santucci, Annalisa

2011-01-01

Aims Atrial Natriuretic Peptide (ANP)-containing amyloid is frequently found in the elderly heart. No data exist regarding ANP aggregation process and its link to pathologies. Our aims were: i) to experimentally prove the presumptive association of Congestive Heart Failure (CHF) and Isolated Atrial Amyloidosis (IAA); ii) to characterize ANP aggregation, thereby elucidating IAA implication in the CHF pathogenesis. Methods and Results A significant prevalence (85%) of IAA was immunohistochemically proven ex vivo in biopsies from CHF patients. We investigated in vitro (using Congo Red, Thioflavin T, SDS-PAGE, transmission electron microscopy, infrared spectroscopy) ANP fibrillogenesis, starting from α-ANP as well as the ability of dimeric β-ANP to promote amyloid formation. Different conditions were adopted, including those reproducing β-ANP prevalence in CHF. Our results defined the uncommon rapidity of α-ANP self-assembly at acidic pH supporting the hypothesis that such aggregates constitute the onset of a fibrillization process subsequently proceeding at physiological pH. Interestingly, CHF-like conditions induced the production of the most stable and time-resistant ANP fibrils suggesting that CHF affected people may be prone to develop IAA. Conclusions We established a link between IAA and CHF by ex vivo examination and assessed that β-ANP is, in vitro, the seed of ANP fibrils. Our results indicate that β-ANP plays a crucial role in ANP amyloid deposition under physiopathological CHF conditions. Overall, our findings indicate that early IAA-related ANP deposition may occur in CHF and suggest that these latter patients should be monitored for the development of cardiac amyloidosis. PMID:21814559

Copolymers of poly-L-lysine with serine and tryptophan form stable DNA vectors: implications for receptor-mediated gene transfer.

PubMed

Gómez-Valadés, A G; Molas, M; Vidal-Alabró, A; Bermúdez, J; Bartrons, R; Perales, J C

2005-01-20

Inefficient gene transfer and poor stability in physiological medium are important shortcomings for receptor-mediated gene transfer vectors. Here, we evaluate vectors formulated with random copolymers of L-lysine/L-serine (3:1) and L-lysine/L-tryptophan (4:1), focusing on both their biophysical and functional characterization. By means of dynamic light scattering (DLS) and transmission electron microscopy (TEM), we demonstrate that poly-L-lysine (pK), poly-L-lysine-L-tryptophan (pKW) and poly-L-lysine-L-serine (pKS) are able to form compacted, small particles when mixed with plasmid DNA in the absence of salt. Upon dilution in physiological medium, copolymers of both lys/ser and lys/trp do not aggregate, in contrast with poly-L-lysine DNA complexes as determined by scattering, DLS and TEM measurements. Tight packing, as demonstrated by resistance to heparin, SDS and trypsin treatments, is also featured in tryptophan-containing complexes. Successful receptor-mediated endocytosis gene transfer using galactosylated copolymers into cells expressing the asiagloglycoprotein receptor correlated with lack of aggregation. Particles obtained using galactosylated poly-L-lysine-L-tryptophan (Gal-pKW) copolymer demonstrated specific receptor-mediated gene transfer since reporter gene activity dropped in the presence of an excess ligand in the culture medium during transfection. Although copolymers of galactosylated poly-L-lysine-L-serine (Gal-pKS) do not aggregate in the presence of salt, they are not able to internalize in a specific receptor-mediated endocytosis fashion. The introduction of bulky aromatic/hydrophobic (tryptophan) or hydrophillic (serine) moieties into the positively charged vectors allows the compacted particles to disperse into salt-containing medium avoiding salt-induced aggregation. Moreover, tryptophan-containing particles are able to mediate specific gene transfer via receptor-mediated endocytosis.

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

[Survival strategy of photosynthetic organisms. 1. Variability of the extent of light-harvesting pigment aggregation as a structural factor optimizing the function of oligomeric photosynthetic antenna. Model calculations].

PubMed

Fetisova, Z G

2004-01-01

In accordance with our concept of rigorous optimization of photosynthetic machinery by a functional criterion, this series of papers continues purposeful search in natural photosynthetic units (PSU) for the basic principles of their organization that we predicted theoretically for optimal model light-harvesting systems. This approach allowed us to determine the basic principles for the organization of a PSU of any fixed size. This series of papers deals with the problem of structural optimization of light-harvesting antenna of variable size controlled in vivo by the light intensity during the growth of organisms, which accentuates the problem of antenna structure optimization because optimization requirements become more stringent as the PSU increases in size. In this work, using mathematical modeling for the functioning of natural PSUs, we have shown that the aggregation of pigments of model light-harvesting antenna, being one of universal optimizing factors, furthermore allows controlling the antenna efficiency if the extent of pigment aggregation is a variable parameter. In this case, the efficiency of antenna increases with the size of the elementary antenna aggregate, thus ensuring the high efficiency of the PSU irrespective of its size; i.e., variation in the extent of pigment aggregation controlled by the size of light-harvesting antenna is biologically expedient.

Family Aggregation and Heritability of ESRD in Taiwan: A Population-Based Study.

PubMed

Wu, Hsin Hsu; Kuo, Chang Fu; Li, I Jung; Weng, Cheng Hao; Lee, Cheng Chia; Tu, Kun Hua; Liu, Shou Hsuan; Chen, Yung Chang; Yang, Chih Wei; Luo, Shue Fen; See, Lai Chu; Yu, Kuang Hui; Huang, Lu Hsiang; Zhang, Weiya; Doherty, Michael; Tian, Ya Chung

2017-11-01

Aggregation of end-stage renal disease (ESRD) has been observed in families of European origin, as well as those of African origin. However, it is not well documented if this disease aggregates in Asian families. Furthermore, the contribution of genetic factors and shared environmental factors to family aggregation remains unclear. Population-based cross-sectional cohort study. All 23,422,955 individuals registered in the Taiwan National Health Insurance Research Database in 2013. Among these, 47.45%, 57.45%, 47.29%, and 1.51% had a known parent, child, sibling, or twin, respectively. We identified 87,849 patients who had a diagnosis of ESRD. Family history of ESRD. ESRD and heritability defined as the proportion of phenotypic variance attributable to genetic factors. Having an affected first-degree relative with ESRD was associated with an adjusted relative risk of 2.46 (95% CI, 2.32-2.62). Relative risks were 96.38 (95% CI, 48.3-192.34) for twins of patients with ESRD, 2.15 (95% CI, 2.02-2.29) for parents, 2.78 (95% CI, 2.53-3.05) for offspring, 4.96 (95% CI, 4.19-5.88) for siblings, and 1.66 (95% CI, 1.54-1.78) for spouses without genetic similarities. Heritability in this study was 31.1% to 11.4% for shared environmental factors and 57.5% for nonshared environmental factors. This was a registry database study and we did not have detailed information about clinical findings or the definite causes of ESRD. This whole population-based family study in Asia confirmed, in a Taiwanese population, that a family history of ESRD is a strong risk factor for this disease. Moderate heritability was noted and environmental factors were related to disease. Family history of ESRD is an important piece of clinical information. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Soil Aggregate Stability and Grassland Productivity Associations in a Northern Mixed-Grass Prairie

PubMed Central

Reinhart, Kurt O.; Vermeire, Lance T.

2016-01-01

Soil aggregate stability data are often predicted to be positively associated with measures of plant productivity, rangeland health, and ecosystem functioning. Here we revisit the hypothesis that soil aggregate stability is positively associated with plant productivity. We measured local (plot-to-plot) variation in grassland community composition, plant (aboveground) biomass, root biomass, % water-stable soil aggregates, and topography. After accounting for spatial autocorrelation, we observed a negative association between % water-stable soil aggregates (0.25–1 and 1–2 mm size classes of macroaggregates) and dominant graminoid biomass, and negative associations between the % water-stable aggregates and the root biomass of a dominant sedge (Carex filifolia). However, variation in total root biomass (0–10 or 0–30 cm depths) was either negatively or not appreciably associated with soil aggregate stabilities. Overall, regression slope coefficients were consistently negative thereby indicating the general absence of a positive association between measures of plant productivity and soil aggregate stability for the study area. The predicted positive association between factors was likely confounded by variation in plant species composition. Specifically, sampling spanned a local gradient in plant community composition which was likely driven by niche partitioning along a subtle gradient in elevation. Our results suggest an apparent trade-off between some measures of plant biomass production and soil aggregate stability, both known to affect the land’s capacity to resist erosion. These findings further highlight the uncertainty of plant biomass-soil stability associations. PMID:27467598

Soil Aggregate Stability and Grassland Productivity Associations in a Northern Mixed-Grass Prairie.

PubMed

Reinhart, Kurt O; Vermeire, Lance T

2016-01-01

Soil aggregate stability data are often predicted to be positively associated with measures of plant productivity, rangeland health, and ecosystem functioning. Here we revisit the hypothesis that soil aggregate stability is positively associated with plant productivity. We measured local (plot-to-plot) variation in grassland community composition, plant (aboveground) biomass, root biomass, % water-stable soil aggregates, and topography. After accounting for spatial autocorrelation, we observed a negative association between % water-stable soil aggregates (0.25-1 and 1-2 mm size classes of macroaggregates) and dominant graminoid biomass, and negative associations between the % water-stable aggregates and the root biomass of a dominant sedge (Carex filifolia). However, variation in total root biomass (0-10 or 0-30 cm depths) was either negatively or not appreciably associated with soil aggregate stabilities. Overall, regression slope coefficients were consistently negative thereby indicating the general absence of a positive association between measures of plant productivity and soil aggregate stability for the study area. The predicted positive association between factors was likely confounded by variation in plant species composition. Specifically, sampling spanned a local gradient in plant community composition which was likely driven by niche partitioning along a subtle gradient in elevation. Our results suggest an apparent trade-off between some measures of plant biomass production and soil aggregate stability, both known to affect the land's capacity to resist erosion. These findings further highlight the uncertainty of plant biomass-soil stability associations.

Absorption and scattering by fractal aggregates and by their equivalent coated spheres

NASA Astrophysics Data System (ADS)

Kandilian, Razmig; Heng, Ri-Liang; Pilon, Laurent

2015-01-01

This paper demonstrates that the absorption and scattering cross-sections and the asymmetry factor of randomly oriented fractal aggregates of spherical monomers can be rapidly estimated as those of coated spheres with equivalent volume and average projected area. This was established for fractal aggregates with fractal dimension ranging from 2.0 to 3.0 and composed of up to 1000 monodisperse or polydisperse monomers with a wide range of size parameter and relative complex index of refraction. This equivalent coated sphere approximation was able to capture the effects of both multiple scattering and shading among constituent monomers on the integral radiation characteristics of the aggregates. It was shown to be superior to the Rayleigh-Debye-Gans approximation and to the equivalent coated sphere approximation proposed by Latimer. However, the scattering matrix element ratios of equivalent coated spheres featured large angular oscillations caused by internal reflection in the coating which were not observed in those of the corresponding fractal aggregates. Finally, the scattering phase function and the scattering matrix elements of aggregates with large monomer size parameter were found to have unique features that could be used in remote sensing applications.

Genome-wide RNA interference screen identifies previously undescribed regulators of polyglutamine aggregation

PubMed Central

Nollen, Ellen A. A.; Garcia, Susana M.; van Haaften, Gijs; Kim, Soojin; Chavez, Alejandro; Morimoto, Richard I.; Plasterk, Ronald H. A.

2004-01-01

Protein misfolding and the formation of aggregates are increasingly recognized components of the pathology of human genetic disease and hallmarks of many neurodegenerative disorders. As exemplified by polyglutamine diseases, the propensity for protein misfolding is associated with the length of polyglutamine expansions and age-dependent changes in protein-folding homeostasis, suggesting a critical role for a protein homeostatic buffer. To identify the complement of protein factors that protects cells against the formation of protein aggregates, we tested transgenic Caenorhabditis elegans strains expressing polyglutamine expansion yellow fluorescent protein fusion proteins at the threshold length associated with the age-dependent appearance of protein aggregation. We used genome-wide RNA interference to identify genes that, when suppressed, resulted in the premature appearance of protein aggregates. Our screen identified 186 genes corresponding to five principal classes of polyglutamine regulators: genes involved in RNA metabolism, protein synthesis, protein folding, and protein degradation; and those involved in protein trafficking. We propose that each of these classes represents a molecular machine collectively comprising the protein homeostatic buffer that responds to the expression of damaged proteins to prevent their misfolding and aggregation. PMID:15084750

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

Modification of an impulse-factoring orbital transfer technique to account for orbit determination and maneuver execution errors

NASA Technical Reports Server (NTRS)

Kibler, J. F.; Green, R. N.; Young, G. R.; Kelly, M. G.

1974-01-01

A method has previously been developed to satisfy terminal rendezvous and intermediate timing constraints for planetary missions involving orbital operations. The method uses impulse factoring in which a two-impulse transfer is divided into three or four impulses which add one or two intermediate orbits. The periods of the intermediate orbits and the number of revolutions in each orbit are varied to satisfy timing constraints. Techniques are developed to retarget the orbital transfer in the presence of orbit-determination and maneuver-execution errors. Sample results indicate that the nominal transfer can be retargeted with little change in either the magnitude (Delta V) or location of the individual impulses. Additonally, the total Delta V required for the retargeted transfer is little different from that required for the nominal transfer. A digital computer program developed to implement the techniques is described.

Molecular mechanisms of platelet activation and aggregation induced by breast cancer cells.

PubMed

Zarà, Marta; Canobbio, Ilaria; Visconte, Caterina; Canino, Jessica; Torti, Mauro; Guidetti, Gianni Francesco

2018-08-01

Tumor cell-induced platelet aggregation represents a critical process both for successful metastatic spread of the tumor and for the development of thrombotic complications in cancer patients. To get further insights into this process, we investigated and compared the molecular mechanisms of platelet aggregation induced by two different breast cancer cell lines (MDA-MB-231 and MCF7) and a colorectal cancer cell line (Caco-2). All the three types of cancer cells were able to induce comparable platelet aggregation, which, however, was observed exclusively in the presence of CaCl 2 and autologous plasma. Aggregation was supported both by fibrinogen binding to integrin αIIbβ3 as well as by fibrin formation, and was completely prevented by the serine protease inhibitor PPACK. Platelet aggregation was preceded by generation of low amounts of thrombin, possibly through tumor cells-expressed tissue factor, and was supported by platelet activation, as revealed by stimulation of phospholipase C, intracellular Ca 2+ increase and activation of Rap1b GTPase. Pharmacological inhibition of phospholipase C, but not of phosphatidylinositol 3-kinase or Src family kinases prevented tumor cell-induced platelet aggregation. Tumor cells also induced dense granule secretion, and the stimulation of the P2Y12 receptor by released ADP was found to be necessary for complete platelet aggregation. By contrast, prevention of thromboxane A 2 synthesis by aspirin did not alter the ability of all the cancer cell lines analyzed to induce platelet aggregation. These results indicate that tumor cell-induced platelet aggregation is not related to the type of the cancer cells or to their metastatic potential, and is triggered by platelet activation and secretion driven by the generation of small amount of thrombin from plasma and supported by the positive feedback signaling through secreted ADP. Copyright © 2018 Elsevier Inc. All rights reserved.

Familial aggregation analysis of gene expressions

PubMed Central

Rao, Shao-Qi; Xu, Liang-De; Zhang, Guang-Mei; Li, Xia; Li, Lin; Shen, Gong-Qing; Jiang, Yang; Yang, Yue-Ying; Gong, Bin-Sheng; Jiang, Wei; Zhang, Fan; Xiao, Yun; Wang, Qing K

2007-01-01

Traditional studies of familial aggregation are aimed at defining the genetic (and non-genetic) causes of a disease from physiological or clinical traits. However, there has been little attempt to use genome-wide gene expressions, the direct phenotypic measures of genes, as the traits to investigate several extended issues regarding the distributions of familially aggregated genes on chromosomes or in functions. In this study we conducted a genome-wide familial aggregation analysis by using the in vitro cell gene expressions of 3300 human autosome genes (Problem 1 data provided to Genetic Analysis Workshop 15) in order to answer three basic genetics questions. First, we investigated how gene expressions aggregate among different types (degrees) of relative pairs. Second, we conducted a bioinformatics analysis of highly familially aggregated genes to see how they are distributed on chromosomes. Third, we performed a gene ontology enrichment test of familially aggregated genes to find evidence to support their functional consensus. The results indicated that 1) gene expressions did aggregate in families, especially between sibs. Of 3300 human genes analyzed, there were a total of 1105 genes with one or more significant (empirical p < 0.05) familial correlation; 2) there were several genomic hot spots where highly familially aggregated genes (e.g., the chromosome 6 HLA genes cluster) were clustered; 3) as we expected, gene ontology enrichment tests revealed that the 1105 genes were aggregating not only in families but also in functional categories. PMID:18466548

Liposomal gene transfer of keratinocyte growth factor improves wound healing by altering growth factor and collagen expression.

PubMed

Pereira, Clifford T; Herndon, David N; Rocker, Roland; Jeschke, Marc G

2007-05-15

Growth factors affect the complex cascade of wound healing; however, interaction between different growth factors during dermal and epidermal regeneration are still not entirely defined. In the present study, we thought to determine the interaction between keratinocyte growth factor (KGF) administered as liposomal cDNA with other dermal and epidermal growth factors and collagen synthesis in an acute wound. Rats received an acute wound and were divided into two groups to receive weekly subcutaneous injections of liposomes plus the Lac-Z gene (0.22 microg, vehicle), or liposomes plus the KGF cDNA (2.2 microg) and Lac-Z gene (0.22 microg). Histological and immunohistochemical techniques were used to determine growth factor, collagen expression, and dermal and epidermal structure. KGF cDNA increased insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-3 (IGFBP-3), and fibroblast growth factor (FGF), decreased transforming growth factor-beta (TGF-beta), while it had no effect on platelet-derived growth factor (PDGF) levels in the wound. KGF cDNA significantly increased collagen Type IV at both the wound edge as well as the wound bed, while it had no effect on collagen Type I and III. KGF cDNA increased re-epithelialization, improved dermal regeneration, and increased neovascularization. Exogenous administered KGF cDNA causes increases in IGF-I, IGF-BP3, FGF, and collagen IV and decreases TGF-beta concentration. KGF gene transfer accelerates wound healing without causing an increase in collagen I or III.

Challenges for simultaneous nitrification, denitrification, and phosphorus removal in microbial aggregates: mass transfer limitation and nitrous oxide production.

PubMed

Meyer, Rikke Louise; Zeng, Raymond Jianxiong; Giugliano, Valerio; Blackall, Linda Louise

2005-05-01

The microbial community composition and activity was investigated in aggregates from a lab-scale bioreactor, in which nitrification, denitrification and phosphorus removal occurred simultaneously. The biomass was highly enriched for polyphosphate accumulating organisms facilitating complete removal of phosphorus from the bulk liquid; however, some inorganic nitrogen still remained at the end of the reactor cycle. This was ascribed to incomplete coupling of nitrification and denitrification causing NO(3)(-) accumulation. After 2 h of aeration, denitrification was dependent on the activity of nitrifying bacteria facilitating the formation of anoxic zones in the aggregates; hence, denitrification could not occur without simultaneous nitrification towards the end of the reactor cycle. Nitrous oxide was identified as a product of denitrification, when based on stored PHA as carbon source. This observation is of critical importance to the outlook of applying PHA-driven denitrification in activated sludge processes.

Discrete stochastic charging of aggregate grains

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Familial Aggregation and Segregation Analysis in Families Presenting Autoimmunity, Polyautoimmunity, and Multiple Autoimmune Syndrome

PubMed Central

Castiblanco, John; Sarmiento-Monroy, Juan Camilo; Mantilla, Ruben Dario; Rojas-Villarraga, Adriana; Anaya, Juan-Manuel

2015-01-01

Studies documenting increased risk of developing autoimmune diseases (ADs) have shown that these conditions share several immunogenetic mechanisms (i.e., the autoimmune tautology). This report explored familial aggregation and segregation of AD, polyautoimmunity, and multiple autoimmune syndrome (MAS) in 210 families. Familial aggregation was examined for first-degree relatives. Segregation analysis was implemented as in S.A.G.E. release 6.3. Data showed differences between late- and early-onset families regarding their age, age of onset, and sex. Familial aggregation of AD in late- and early-onset families was observed. For polyautoimmunity as a trait, only aggregation was observed between sibling pairs in late-onset families. No aggregation was observed for MAS. Segregation analyses for AD suggested major gene(s) with no clear discernible classical known Mendelian transmission in late-onset families, while for polyautoimmunity and MAS no model was implied. Data suggest that polyautoimmunity and MAS are not independent traits and that gender, age, and age of onset are interrelated factors influencing autoimmunity. PMID:26697508

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

PubMed

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

2011-06-01

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

HEALTH AND ENVIRONMENTAL SCIENCES INSTITUTE'S EXPOSURE FACTORS DATABASE FOR AGGREGATE AND CUMULATIVE RISK ASSESSMENT

EPA Science Inventory

In recent years, the risk analysis community has broadened its use of complex aggregate and cumulative residential exposure models (e.g., to meet the requirements of the 1996 Food Quality Protection Act). The value of these models is their ability to incorporate a range of input...

Influence of Aggregate Gradation on the Longitudinal Wave Velocity Changes in Unloaded Concrete

NASA Astrophysics Data System (ADS)

Teodorczyk, Michał

2017-10-01

Diagnosis is an important factor in the assessment of structural and operational condition of a concrete structure. Among diagnostic methods, non-destructive testing methods play a special role. Acoustic emission evaluation based on the identification and location of destructive processes is one of such methods. The 3D location of AE events and moment tensor of fracture analysis are calculated by longitudinal wave velocity. Therefore, determining the velocity of longitudinal wave of concrete and the impact of the material and destructive factors are of essential importance. This paper reports the investigation of the effect of aggregate gradation on the change in wave velocity of unloaded concrete. The investigation was carried out on six 150 x 150 x 600 mm elements. Three elements contained aggregate fraction 8/16 mm and the other three were made with aggregate fraction 2/16 mm. Two acoustic emission sensors were used on the surface of the elements, and the wave was generated by the Hsu - Nielsen source. Longitudinal wave velocities for each group of elements were calculated and statistical test of significance was used for the comparison of two means. The results of the test indicated a substantial effect of the aggregate grain size on the change in longitudinal wave velocity. The average wave velocity in the concrete containing 8/16 mm fraction was 4672 m/s. In the concrete with 2/16 mm fraction, the velocity decreased to 4373 m/s. The velocity of the wave decreases at larger quantities of aggregate. The propagating longitudinal wave encounters more aggregate grains on its way and is reflected, also from air voids, multiple times and so its velocity is noticeably lower in the concrete with the 2/16 fraction. Thus, to be able to accurately locate AE events and analyse moment tensor during concrete structure testing, the aggregate grain size used in the concrete should be taken into account.

Development of a general equation to determine the transfer factor feed-to-meat for radiocesium on the basis of the body mass of domestic animals

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

Nalezinski, S.; Ruehm, W.; Wirth, E.

1996-05-01

Transfer factors from feed to meat (5{sub {integral}}), taken from literature for monogastric animals and ruminants have been correlated to their corresponding animal body mass (m{sub b}). Taking all data into account, a close relationship between both transfer factor and body mass becomes evident, yielding a regression function of (T{sub {integral}} = 8.0 x m{sub b}{sup {minus}0.91}) (r = -0.97). For monogastric animals (including poultry), the corresponding relationships are T{sub {integral}} = 1.9 x m{sub b}{sup {minus}0.72} (r = 0.78). The equations offer the opportunity to estimate the transfer factor for individual animals more precisely taking individual body masses intomore » account. They are of interest for animals, on which no or only poor data concerning radiocesium transfer factors are available. The determination of radiocesium transfer factors are reduced to a simple weighing process. 17 refs., 1 fig., 2 tabs.« less

Composition, buoyancy regulation and fate of ice algal aggregates in the Central Arctic Ocean.

PubMed

Fernández-Méndez, Mar; Wenzhöfer, Frank; Peeken, Ilka; Sørensen, Heidi L; Glud, Ronnie N; Boetius, Antje

2014-01-01

Sea-ice diatoms are known to accumulate in large aggregates in and under sea ice and in melt ponds. There is recent evidence from the Arctic that such aggregates can contribute substantially to particle export when sinking from the ice. The role and regulation of microbial aggregation in the highly seasonal, nutrient- and light-limited Arctic sea-ice ecosystem is not well understood. To elucidate the mechanisms controlling the formation and export of algal aggregates from sea ice, we investigated samples taken in late summer 2011 and 2012, during two cruises to the Eurasian Basin of the Central Arctic Ocean. Spherical aggregates densely packed with pennate diatoms, as well as filamentous aggregates formed by Melosira arctica showed sign of different stages of degradation and physiological stoichiometries, with carbon to chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen molar ratios of 8-35 and 9-40, respectively. Sub-ice algal aggregate densities ranged between 1 and 17 aggregates m(-2), maintaining an estimated net primary production of 0.4-40 mg C m(-2) d(-1), and accounted for 3-80% of total phototrophic biomass and up to 94% of local net primary production. A potential factor controlling the buoyancy of the aggregates was light intensity, regulating photosynthetic oxygen production and the amount of gas bubbles trapped within the mucous matrix, even at low ambient nutrient concentrations. Our data-set was used to evaluate the distribution and importance of Arctic algal aggregates as carbon source for pelagic and benthic communities.

Composition, Buoyancy Regulation and Fate of Ice Algal Aggregates in the Central Arctic Ocean

PubMed Central

Fernández-Méndez, Mar; Wenzhöfer, Frank; Peeken, Ilka; Sørensen, Heidi L.; Glud, Ronnie N.; Boetius, Antje

2014-01-01

Sea-ice diatoms are known to accumulate in large aggregates in and under sea ice and in melt ponds. There is recent evidence from the Arctic that such aggregates can contribute substantially to particle export when sinking from the ice. The role and regulation of microbial aggregation in the highly seasonal, nutrient- and light-limited Arctic sea-ice ecosystem is not well understood. To elucidate the mechanisms controlling the formation and export of algal aggregates from sea ice, we investigated samples taken in late summer 2011 and 2012, during two cruises to the Eurasian Basin of the Central Arctic Ocean. Spherical aggregates densely packed with pennate diatoms, as well as filamentous aggregates formed by Melosira arctica showed sign of different stages of degradation and physiological stoichiometries, with carbon to chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen molar ratios of 8–35 and 9–40, respectively. Sub-ice algal aggregate densities ranged between 1 and 17 aggregates m−2, maintaining an estimated net primary production of 0.4–40 mg C m−2 d−1, and accounted for 3–80% of total phototrophic biomass and up to 94% of local net primary production. A potential factor controlling the buoyancy of the aggregates was light intensity, regulating photosynthetic oxygen production and the amount of gas bubbles trapped within the mucous matrix, even at low ambient nutrient concentrations. Our data-set was used to evaluate the distribution and importance of Arctic algal aggregates as carbon source for pelagic and benthic communities. PMID:25208058

Greater Collagen‐Induced Platelet Aggregation Following Cyclooxygenase 1 Inhibition Predicts Incident Acute Coronary Syndromes

PubMed Central

Becker, Diane M.; Yanek, Lisa R.; Faraday, Nauder; Vaidya, Dhananjay; Mathias, Rasika; Kral, Brian G.; Becker, Lewis C.

2014-01-01

Abstract Greater ex vivo platelet aggregation to agonists may identify individuals at risk of acute coronary syndromes (ACS). However, increased aggregation to a specific agonist may be masked by inherent variability in other activation pathways. In this study, we inhibited the cyclooxygenase‐1 (COX1) pathway with 2‐week aspirin therapy and measured residual aggregation to collagen and ADP to determine whether increased aggregation in a non‐COX1 pathway is associated with incident ACS. We assessed ex vivo whole blood platelet aggregation in 1,699 healthy individuals with a family history of early‐onset coronary artery disease followed for 6±1.2 years. Incident ACS events were observed in 22 subjects. Baseline aggregation was not associated with ACS. After COX1 pathway inhibition, collagen‐induced aggregation was significantly greater in participants with ACS compared with those without (29.0 vs. 23.6 ohms, p < 0.001). In Cox proportional hazards models, this association remained significant after adjusting for traditional cardiovascular risk factors (HR = 1.10, 95%CI = 1.06–1.15; p < 0.001). In contrast, ADP‐induced aggregation after COX1 inhibition was not associated with ACS. After COX1 pathway inhibition, subjects with greater collagen‐induced platelet aggregation demonstrated a significant excess risk of incident ACS. These data suggest that platelet activation related to collagen may play an important role in the risk of ACS. PMID:25066685

Verification of radionuclide transfer factors to domestic-animal food products, using indigenous elements and with emphasis on iodine.

PubMed

Sheppard, S C; Long, J M; Sanipelli, B

2010-11-01

Recent reviews have established benchmark values for transfer factors that describe radionuclide transfer from plants to animal food product such as milk, eggs and meat. They also illustrate the paucity of data for some elements and some food products. The present study quantified transfer data using indigenous elements measured in dairy, poultry and other livestock farms in Canada. Up to 62 elements are reported, with particular emphasis on iodine (I) because of the need to accurately assess the behaviour of (129)I from disposal of nuclear fuel waste. There was remarkable agreement with the literature values, and for many elements the present study involved many more observations than were previously available. Perhaps the most important observation was that product/substrate concentration ratios (CR) were quite consistent across species, whereas the traditional fractional transfer factors (TF, units of d kg(-1) or d L(-1)) necessarily vary with body mass (feed intake). This suggests that for long-term assessments, it may be advisable to change the models to use CR rather than TF.

Understanding curcumin-induced modulation of protein aggregation.

PubMed

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

2017-07-01

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

Stability of Iowa mutant and wild type Aβ-peptide aggregates

NASA Astrophysics Data System (ADS)

Alred, Erik J.; Scheele, Emily G.; Berhanu, Workalemahu M.; Hansmann, Ulrich H. E.

2014-11-01

Recent experiments indicate a connection between the structure of amyloid aggregates and their cytotoxicity as related to neurodegenerative diseases. Of particular interest is the Iowa Mutant, which causes early-onset of Alzheimer's disease. While wild-type Amyloid β-peptides form only parallel beta-sheet aggregates, the mutant also forms meta-stable antiparallel beta sheets. Since these structural variations may cause the difference in the pathological effects of the two Aβ-peptides, we have studied in silico the relative stability of the wild type and Iowa mutant in both parallel and antiparallel forms. We compare regular molecular dynamics simulations with such where the viscosity of the samples is reduced, which, we show, leads to higher sampling efficiency. By analyzing and comparing these four sets of all-atom molecular dynamics simulations, we probe the role of the various factors that could lead to the structural differences. Our analysis indicates that the parallel forms of both wild type and Iowa mutant aggregates are stable, while the antiparallel aggregates are meta-stable for the Iowa mutant and not stable for the wild type. The differences result from the direct alignment of hydrophobic interactions in the in-register parallel oligomers, making them more stable than the antiparallel aggregates. The slightly higher thermodynamic stability of the Iowa mutant fibril-like oligomers in its parallel organization over that in antiparallel form is supported by previous experimental measurements showing slow inter-conversion of antiparallel aggregates into parallel ones. Knowledge of the mechanism that selects between parallel and antiparallel conformations and determines their relative stability may open new avenues for the development of therapies targeting familial forms of early-onset Alzheimer's disease.

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

Largely ignored: the impact of the threshold value for a QALY on the importance of a transferability factor.

PubMed

Vemer, Pepijn; Rutten-van Mölken, Maureen P M H

2011-10-01

Recently, several checklists systematically assessed factors that affect the transferability of cost-effectiveness (CE) studies between jurisdictions. The role of the threshold value for a QALY has been given little consideration in these checklists, even though the importance of a factor as a cause of between country differences in CE depends on this threshold. In this paper, we study the impact of the willingness-to-pay (WTP) per QALY on the importance of transferability factors in the case of smoking cessation support (SCS). We investigated, for several values of the WTP, how differences between six countries affect the incremental net monetary benefit (INMB) of SCS. The investigated factors were demography, smoking prevalence, mortality, epidemiology and costs of smoking-related diseases, resource use and unit costs of SCS, utility weights and discount rates. We found that when the WTP decreased, factors that mainly affect health outcomes became less important and factors that mainly effect costs became more important. With a WTP below 1,000, the factors most responsible for between country differences in INMB were resource use and unit costs of SCS and the costs of smoking-related diseases. Utility values had little impact. At a threshold above 10,000, between country differences were primarily due to different discount rates, utility weights and epidemiology of smoking-related diseases. Costs of smoking-related diseases had little impact. At all thresholds, demography had little impact. We concluded that, when judging the transferability of a CE study, we should consider the between country differences in WTP threshold values.

Analysis of aggregated tick returns: Evidence for anomalous diffusion

NASA Astrophysics Data System (ADS)

Weber, Philipp

2007-01-01

In order to investigate the origin of large price fluctuations, we analyze stock price changes of ten frequently traded NASDAQ stocks in the year 2002. Though the influence of the trading frequency on the aggregate return in a certain time interval is important, it cannot alone explain the heavy-tailed distribution of stock price changes. For this reason, we analyze intervals with a fixed number of trades in order to eliminate the influence of the trading frequency and investigate the relevance of other factors for the aggregate return. We show that in tick time the price follows a discrete diffusion process with a variable step width while the difference between the number of steps in positive and negative direction in an interval is Gaussian distributed. The step width is given by the return due to a single trade and is long-term correlated in tick time. Hence, its mean value can well characterize an interval of many trades and turns out to be an important determinant for large aggregate returns. We also present a statistical model reproducing the cumulative distribution of aggregate returns. For an accurate agreement with the empirical distribution, we also take into account asymmetries of the step widths in different directions together with cross correlations between these asymmetries and the mean step width as well as the signs of the steps.

Aggregate-level lead exposure, gun violence, homicide, and rape.

PubMed

Boutwell, Brian B; Nelson, Erik J; Qian, Zhengmin; Vaughn, Michael G; Wright, John P; Beaver, Kevin M; Barnes, J C; Petkovsek, Melissa; Lewis, Roger; Schootman, Mario; Rosenfeld, Richard

2017-01-01

An increasing body of research has linked the geographic distribution of lead with various indicators of criminal and antisocial behavior. The current study, using data from an ongoing project related to lead exposure in St. Louis City, MO, analyzed the association between aggregate blood lead levels and specific indicators violent crime within the city. Ecological study. St. Louis, Missouri. Blood lead levels. Official reports of violent crimes were categorized as 1) crimes involving a firearm (yes/no), 2) assault crimes (with or without a firearm), 3) robbery crimes (with or without a firearm), 4) homicides and 5) rape. With the exception of rape, aggregate blood-lead levels were statistically significant predictors of violent crime at the census tract level. The risk ratios for each of the outcome measures were as follows: firearm crimes 1.03 (1.03-1.04), assault crimes 1.03 (1.02-1.03), robbery crimes 1.03 (1.02-1.04), homicide 1.03 (1.01, 1.04), and rape 1.01 (0.99-1.03). Extending prior research in St. Louis, results suggest that aggregated lead exposure at the census tract level predicted crime outcomes, even after accounting for important sociological variables. Moving forward, a more developed understanding of aggregate level crime may necessitate a shift toward studying the synergy between sociological and biological risk factors such as lead exposure.

Polyglutamine aggregation in Huntington and related diseases.

PubMed

Polling, Saskia; Hill, Andrew F; Hatters, Danny M

2012-01-01

Polyglutamine (polyQ)-expansions in different proteins cause nine neurodegenerative diseases. While polyQ aggregation is a key pathological hallmark of these diseases, how aggregation relates to pathogenesis remains contentious. In this chapter, we review what is known about the aggregation process and how cells respond and interact with the polyQ-expanded proteins. We cover detailed biophysical and structural studies to uncover the intrinsic features of polyQ aggregates and concomitant effects in the cellular environment. We also examine the functional consequences ofpolyQ aggregation and how cells may attempt to intervene and guide the aggregation process.

Neisseria gonorrhoeae Aggregation Reduces Its Ceftriaxone Susceptibility.

PubMed

Wang, Liang-Chun; Litwin, Madeline; Sahiholnasab, Zahraossadat; Song, Wenxia; Stein, Daniel C

2018-06-15

Antibiotic resistance in Neisseria gonorrhoeae (GC) has become an emerging threat worldwide and heightens the need for monitoring treatment failures. N. gonorrhoeae , a gram-negative bacterium responsible for gonorrhea, infects humans exclusively and can form aggregates during infection. While minimal inhibitory concentration (MIC) tests are often used for determining antibiotic resistance development and treatment, the knowledge of the true MIC in individual patients and how it relates to this laboratory measure is not known. We examined the effect of aggregation on GC antibiotic susceptibility and the relationship between bacterial aggregate size and their antibiotic susceptibility. Aggregated GC have a higher survival rate when treated with ceftriaxone than non-aggregated GC, with bacteria in the core of the aggregates surviving the treatment. GC lacking opacity-associated protein or pili, or expressing a truncated lipooligosaccharide, three surface molecules that mediate GC-GC interactions, reduce both aggregation and ceftriaxone survival. This study demonstrates that the aggregation of N. gonorrhoeae can reduce the susceptibility to antibiotics, and suggests that antibiotic utilization can select for GC surface molecules that promote aggregation which in turn drive pathogen evolution. Inhibiting aggregation may be a potential way of increasing the efficacy of ceftriaxone treatment, consequently reducing treatment failure.

Picomolar platelet-activating factor mobilizes Ca to change platelet shape without activating phospholipase C or protein kinase C; simultaneous fluorometric measurement of intracellular free Ca concentration and aggregation.

PubMed

James-Kracke, M R; Sexe, R B; Shukla, S D

1994-11-01

The purpose of this study was to investigate signal transduction mechanisms activated by low and high concentrations of platelet-activating factor (PAF) in rabbit platelets and to contrast the responses to those induced by thrombin. We measured changes in intracellular free calcium ([Ca++]i) with fura2, while monitoring light scatter simultaneously as a measure of shape change and aggregation in a dual-excitation dual-emission spectrofluorometer. An abrupt 20% fall in light scatter, coincident with the peak of the [Ca++]i, indicated shape change in Ca-containing or Ca-free medium and was blocked by BAPTA loading and 10 microM cytochalasin B. A secondary decline in light scatter, indicating aggregation, occurred only in Ca-containing medium and only under conditions favoring protein kinase C (PKC) activation. PAF at 10(-12) M did not increase 1,4,5-inositol triphosphate content, which suggested PKC would not be activated. However, PAF at 10(-12) rapidly increased [Ca++]i to 900 nM in 7 sec seemingly by Ca influx through receptor-operated channels inducing shape change. PAF at 10(-9) and 10(-8) M increased [Ca++]i to 2 microM in 12 sec and induced both shape change and aggregation. However, in platelets pretreated with 100 nM staurosporine to inhibit protein kinases, 10(-9) M PAF did not cause aggregation even though [Ca++]i still rose to 2 microM, which indicated that PKC plays a role in aggregation but not in Ca++ mobilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced levels of soluble CD40 ligand exacerbate platelet aggregation and thrombus formation through a CD40-dependent tumor necrosis factor receptor-associated factor-2/Rac1/p38 mitogen-activated protein kinase signaling pathway.

PubMed

Yacoub, Daniel; Hachem, Ahmed; Théorêt, Jean-François; Gillis, Marc-Antoine; Mourad, Walid; Merhi, Yahye

2010-12-01

CD40 ligand is a thromboinflammatory molecule that predicts cardiovascular events. Platelets constitute the major source of soluble CD40 ligand (sCD40L), which has been shown to influence platelet activation, although its exact functional impact on platelets and the underlying mechanisms remain undefined. We aimed to determine the impact and the signaling mechanisms of sCD40L on platelets. sCD40L strongly enhances platelet activation and aggregation. Human platelets treated with a mutated form of sCD40L that does not bind CD40, and CD40(-/-) mouse platelets failed to elicit such responses. Furthermore, sCD40L stimulation induces the association of the tumor necrosis factor receptor-associated factor-2 with platelet CD40. Notably, sCD40L primes platelets through activation of the small GTPase Rac1 and its downstream target p38 mitogen-activated protein kinase, which leads to platelet shape change and actin polymerization. Moreover, sCD40L exacerbates thrombus formation and leukocyte infiltration in wild-type mice but not in CD40(-/-) mice. sCD40L enhances agonist-induced platelet activation and aggregation through a CD40-dependent tumor necrosis factor receptor-associated factor-2/Rac1/p38 mitogen-activated protein kinase signaling pathway. Thus, sCD40L is an important platelet primer predisposing platelets to enhanced thrombus formation in response to vascular injury. This may explain the link between circulating levels of sCD40L and cardiovascular diseases.

Excavation and aggregation as organizing factors in de novo construction by mound-building termites.

PubMed

Green, Ben; Bardunias, Paul; Turner, J Scott; Nagpal, Radhika; Werfel, Justin

2017-06-14

Termites construct complex mounds that are orders of magnitude larger than any individual and fulfil a variety of functional roles. Yet the processes through which these mounds are built, and by which the insects organize their efforts, remain poorly understood. The traditional understanding focuses on stigmergy, a form of indirect communication in which actions that change the environment provide cues that influence future work. Termite construction has long been thought to be organized via a putative 'cement pheromone': a chemical added to deposited soil that stimulates further deposition in the same area, thus creating a positive feedback loop whereby coherent structures are built up. To investigate the detailed mechanisms and behaviours through which termites self-organize the early stages of mound construction, we tracked the motion and behaviour of major workers from two Macrotermes species in experimental arenas. Rather than a construction process focused on accumulation of depositions, as models based on cement pheromone would suggest, our results indicated that the primary organizing mechanisms were based on excavation. Digging activity was focused on a small number of excavation sites, which in turn provided templates for soil deposition. This behaviour was mediated by a mechanism of aggregation, with termites being more likely to join in the work at an excavation site as the number of termites presently working at that site increased. Statistical analyses showed that this aggregation mechanism was a response to active digging, distinct from and unrelated to putative chemical cues that stimulate deposition. Agent-based simulations quantitatively supported the interpretation that the early stage of de novo construction is primarily organized by excavation and aggregation activity rather than by stigmergic deposition. © 2017 The Author(s).

Excavation and aggregation as organizing factors in de novo construction by mound-building termites

PubMed Central

Bardunias, Paul; Turner, J. Scott; Nagpal, Radhika; Werfel, Justin

2017-01-01

Termites construct complex mounds that are orders of magnitude larger than any individual and fulfil a variety of functional roles. Yet the processes through which these mounds are built, and by which the insects organize their efforts, remain poorly understood. The traditional understanding focuses on stigmergy, a form of indirect communication in which actions that change the environment provide cues that influence future work. Termite construction has long been thought to be organized via a putative ‘cement pheromone’: a chemical added to deposited soil that stimulates further deposition in the same area, thus creating a positive feedback loop whereby coherent structures are built up. To investigate the detailed mechanisms and behaviours through which termites self-organize the early stages of mound construction, we tracked the motion and behaviour of major workers from two Macrotermes species in experimental arenas. Rather than a construction process focused on accumulation of depositions, as models based on cement pheromone would suggest, our results indicated that the primary organizing mechanisms were based on excavation. Digging activity was focused on a small number of excavation sites, which in turn provided templates for soil deposition. This behaviour was mediated by a mechanism of aggregation, with termites being more likely to join in the work at an excavation site as the number of termites presently working at that site increased. Statistical analyses showed that this aggregation mechanism was a response to active digging, distinct from and unrelated to putative chemical cues that stimulate deposition. Agent-based simulations quantitatively supported the interpretation that the early stage of de novo construction is primarily organized by excavation and aggregation activity rather than by stigmergic deposition. PMID:28615497

Excited-state dynamics of astaxanthin aggregates

NASA Astrophysics Data System (ADS)

Fuciman, Marcel; Durchan, Milan; Šlouf, Václav; Keşan, Gürkan; Polívka, Tomáš

2013-05-01

Astaxanthin forms three types of aggregates in hydrated dimethyl sulfoxide (DMSO). In DMSO/water ratio of 1:1, a red-shifted J-aggregate with maximum at 570 nm is generated, while a ratio of 1:9 produces blue-shifted H-aggregates with peaks at 386 nm (H1) and 460 nm (H2). Monomeric astaxanthin in DMSO has an S1 lifetime of 5.3 ps, but a long-lived (33 ps) S∗ signal was also identified. Aggregation changes the S1 lifetimes to 17 ps (H1), 30 ps (H2), and 14 ps (J). Triplet state of astaxanthin, most likely generated via singlet homofission, was observed in H1 and H2 aggregates.

Factors related to clinical pregnancy after vitrified-warmed embryo transfer: a retrospective and multivariate logistic regression analysis of 2313 transfer cycles.

PubMed

Shi, Wenhao; Zhang, Silin; Zhao, Wanqiu; Xia, Xue; Wang, Min; Wang, Hui; Bai, Haiyan; Shi, Juanzi

2013-07-01

What factors does multivariate logistic regression show to be significantly associated with the likelihood of clinical pregnancy in vitrified-warmed embryo transfer (VET) cycles? Assisted hatching (AH) and if the reason to freeze embryos was to avoid the risk of ovarian hyperstimulation syndrome (OHSS) were significantly positively associated with a greater likelihood of clinical pregnancy. Single factor analysis has shown AH, number of embryos transferred and the reason of freezing for OHSS to be positively and damaged blastomere to be negatively significantly associated with the chance of clinical pregnancy after VET. It remains unclear what factors would be significant after multivariate analysis. The study was a retrospective analysis of 2313 VET cycles from 1481 patients performed between January 2008 and April 2012. A multivariate logistic regression analysis was performed to identify the factors to affect clinical pregnancy outcome of VET. There were 22 candidate variables selected based on clinical experiences and the literature. With the thresholds of α entry = α removal= 0.05 for both variable entry and variable removal, eight variables were chosen to contribute the multivariable model by the bootstrap stepwise variable selection algorithm (n = 1000). Eight variables were age at controlled ovarian hyperstimulation (COH), reason for freezing, AH, endometrial thickness, damaged blastomere, number of embryos transferred, number of good-quality embryos, and blood presence on transfer catheter. A descriptive comparison of the relative importance was accomplished by the proportion of explained variation (PEV). Among the reasons for freezing, the OHSS group showed a higher OR than the surplus embryo group when compared with other reasons for VET groups (OHSS versus Other, OR: 2.145; CI: 1.4-3.286; Surplus embryos versus Other, OR: 1.152; CI: 0.761-1.743) and high PEV (marginal 2.77%, P = 0.2911; partial 1.68%; CI of area under receptor operator characteristic

Spectroscopic manifestations of hybrid association of CdS colloidal quantum dots with J-aggregates of a thiatrimethine cyanine dye

NASA Astrophysics Data System (ADS)

Ovchinnikov, O. V.; Smirnov, M. S.; Shapiro, B. I.; Dedikova, A. O.; Shatskikh, T. S.

2015-11-01

We have found spectroscopic manifestations of hybrid association in mixtures of CdS colloidal quantum dots with an average size of 2.5-4.2 nm with J-aggregates of pyridinium salt of the 3,3'-di-(γ- sulfopropyl)-9-ethyl-4,5,4',5'-dibenzo-thiacarbocyanine betaine dye that were prepared by the sol-gel method in gelatin. Observed changes of the spectral properties of J-aggregates of dye molecules due to their hybrid association with CdS quantum dots are ensured by steric transformations of dye molecules, which lead to the formation of luminescent trans-J-aggregates. The hybrid association is accompanied by the quenching of the recombination luminescence band of CdS quantum dots (540-640 nm) and by an increase in the luminescence intensity of J-aggregates of dye molecules (670-680 nm). This regularity becomes enhanced with an increase in the ratio of the number of dye molecules to the number of quantum dots [ n dye]: [ n QD] and in the degree of overlap between the luminescence spectrum of quantum dots and the absorption spectrum of J-aggregates, which indicates that there is a resonant nonradiative transfer of the electronic excitation energy from recombination luminescence centers in CdS quantum dots to trans-J-aggregates of dye molecules conjugated to them.

Rigid aggregates: theory and applications

NASA Astrophysics Data System (ADS)

Richardson, D. C.

2005-08-01

Numerical models employing ``perfect'' self-gravitating rubble piles that consist of monodisperse rigid spheres with configurable contact dissipation have been used to explore collisional and rotational disruption of gravitational aggregates. Applications of these simple models include numerical simulations of planetesimal evolution, asteroid family formation, tidal disruption, and binary asteroid formation. These studies may be limited by the idealized nature of the rubble pile model, since perfect identical spheres stack and shear in a very specific, possibly over-idealized way. To investigate how constituent properties affect the overall characteristics of a gravitational aggregate, particularly its failure modes, we have generalized our numerical code to model colliding, self-gravitating, rigid aggregates made up of variable-size spheres. Euler's equation of rigid-body motion in the presence of external torques are implemented, along with a self-consistent prescription for handling non-central impacts. Simple rules for sticking and breaking are also included. Preliminary results will be presented showing the failure modes of gravitational aggregates made up of smaller, rigid, non-idealized components. Applications of this new capability include more realistic aggregate models, convenient modeling of arbitrary rigid shapes for studies of the stability of orbiting companions (replacing one or both bodies with rigid aggregates eliminates expensive interparticle collisions while preserving the shape, spin, and gravity field of the bodies), and sticky particle aggregation in dense planetary rings. This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. NAG511722 issued through the Office of Space Science and by the National Science Foundation under Grant No. AST0307549.

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

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

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

PubMed Central

Wang, Dongsheng; Feng, Decheng

2014-01-01

Adhesion between asphalt and aggregate plays an important role in the performance of asphalt mixtures. A low-frequency adhesion fatigue test was proposed in this paper to study the effect of environment on the asphalt-aggregate adhesion system. The stress-based fatigue model had been utilized to describe the fatigue behavior of thin-film asphalt and aggregate system. The factors influencing the adhesion fatigue performance were also investigated. Experiment results show that asphalt has more important effect on the adhesion performance comparing with aggregate. Basalt, which is regarded as hydrophobic aggregates with low silica content, has better adhesion performance to asphalt binder when compared with granite. The effects of aging on the adhesion fatigue performance are different for PG64-22 and rubber asphalt. Long-term aging is found to reduce the adhesion fatigue lives for rubber asphalt and aggregate system, while the effect of long-term aging for aggregate and PG64-22 binder system is positive. Generally the increased stress amplitude and test temperature could induce greater damage and lead to less fatigue lives for adhesion test system. PMID:25054187

Modelling and laboratory studies on the adhesion fatigue performance for thin-film asphalt and aggregate system.

PubMed

Wang, Dongsheng; Yi, Junyan; Feng, Decheng

2014-01-01

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

Flow Partitioning in Fully Saturated Soil Aggregates

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

Yang, Xiaofan; Richmond, Marshall C.; Scheibe, Timothy D.

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 flowmore » 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

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.

Structure-based inhibitors of tau aggregation