Fast sparsely synchronized brain rhythms in a scale-free neural network.

PubMed

Kim, Sang-Yoon; Lim, Woochang

2015-08-01

We consider a directed version of the Barabási-Albert scale-free network model with symmetric preferential attachment with the same in- and out-degrees and study the emergence of sparsely synchronized rhythms for a fixed attachment degree in an inhibitory population of fast-spiking Izhikevich interneurons. Fast sparsely synchronized rhythms with stochastic and intermittent neuronal discharges are found to appear for large values of J (synaptic inhibition strength) and D (noise intensity). For an intensive study we fix J at a sufficiently large value and investigate the population states by increasing D. For small D, full synchronization with the same population-rhythm frequency fp and mean firing rate (MFR) fi of individual neurons occurs, while for large D partial synchronization with fp>〈fi〉 (〈fi〉: ensemble-averaged MFR) appears due to intermittent discharge of individual neurons; in particular, the case of fp>4〈fi〉 is referred to as sparse synchronization. For the case of partial and sparse synchronization, MFRs of individual neurons vary depending on their degrees. As D passes a critical value D* (which is determined by employing an order parameter), a transition to unsynchronization occurs due to the destructive role of noise to spoil the pacing between sparse spikes. For D

Assessment of attachment behaviour to human caregivers in wolf pups (Canis lupus lupus).

PubMed

Hall, Nathaniel J; Lord, Kathryn; Arnold, Anne-Marie K; Wynne, Clive D L; Udell, Monique A R

2015-01-01

Previous research suggested that 16-week old dog pups, but not wolf pups, show attachment behaviour to a human caregiver. Attachment to a caregiver in dog pups has been demonstrated by differential responding to a caregiver compared to a stranger in the Ainsworth Strange Situation Test. We show here that 3-7 week old wolf pups also show attachment-like behaviour to a human caregiver as measured by preferential proximity seeking, preferential contact, and preferential greeting to a human caregiver over a human stranger in a modified and counterbalanced version of the Ainsworth Strange Situation Test. In addition, our results show that preferential responding to a caregiver over a stranger is only apparent following brief isolation. In initial episodes, wolf pups show no differentiation between the caregiver and the stranger; however, following a 2-min separation, the pups show proximity seeking, more contact, and more greeting to the caregiver than the stranger. These results suggest intensive human socialization of a wolf can lead to attachment--like responding to a human caregiver during the first two months of a wolf pup's life. Published by Elsevier B.V.

Role of dimensionality in preferential attachment growth in the Bianconi-Barabási model

NASA Astrophysics Data System (ADS)

Nunes, Thiago C.; Brito, Samurai; da Silva, Luciano R.; Tsallis, Constantino

2017-09-01

Scale-free networks are quite popular nowadays since many systems are well represented by such structures. In order to study these systems, several models were proposed. However, most of them do not take into account the node-to-node Euclidean distance, i.e. the geographical distance. In real networks, the distance between sites can be very relevant, e.g. those cases where it is intended to minimize costs. Within this scenario we studied the role of dimensionality d in the Bianconi-Barabási model with a preferential attachment growth involving Euclidean distances. The preferential attachment in this model follows the rule \\Pii \\propto ηi k_i/rijα_A (1 ≤slant i < j; αA ≥slant 0) , where ηi characterizes the fitness of the ith site and is randomly chosen within the (0, 1] interval. We verified that the degree distribution P(k) for dimensions d=1, 2, 3, 4 are well fitted by P(k) \\propto e_q-k/κ , where e_q-k/κ is the q-exponential function naturally emerging within nonextensive statistical mechanics. We determine the index q and κ as functions of the quantities αA and d, and numerically verify that both present a universal behavior with respect to the scaled variable α_A/d . The same behavior also has been displayed by the dynamical β exponent which characterizes the steadily growing number of links of a given site.

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Consensus of Multi-Agent Systems with Prestissimo Scale-Free Networks

NASA Astrophysics Data System (ADS)

Yang, Hong-Yong; Lu, Lan; Cao, Ke-Cai; Zhang, Si-Ying

2010-04-01

In this paper, the relations of the network topology and the moving consensus of multi-agent systems are studied. A consensus-prestissimo scale-free network model with the static preferential-consensus attachment is presented on the rewired link of the regular network. The effects of the static preferential-consensus BA network on the algebraic connectivity of the topology graph are compared with the regular network. The robustness gain to delay is analyzed for variable network topology with the same scale. The time to reach the consensus is studied for the dynamic network with and without communication delays. By applying the computer simulations, it is validated that the speed of the convergence of multi-agent systems can be greatly improved in the preferential-consensus BA network model with different configuration.

Popularity versus similarity in growing networks.

PubMed

Papadopoulos, Fragkiskos; Kitsak, Maksim; Serrano, M Ángeles; Boguñá, Marián; Krioukov, Dmitri

2012-09-27

The principle that 'popularity is attractive' underlies preferential attachment, which is a common explanation for the emergence of scaling in growing networks. If new connections are made preferentially to more popular nodes, then the resulting distribution of the number of connections possessed by nodes follows power laws, as observed in many real networks. Preferential attachment has been directly validated for some real networks (including the Internet), and can be a consequence of different underlying processes based on node fitness, ranking, optimization, random walks or duplication. Here we show that popularity is just one dimension of attractiveness; another dimension is similarity. We develop a framework in which new connections optimize certain trade-offs between popularity and similarity, instead of simply preferring popular nodes. The framework has a geometric interpretation in which popularity preference emerges from local optimization. As opposed to preferential attachment, our optimization framework accurately describes the large-scale evolution of technological (the Internet), social (trust relationships between people) and biological (Escherichia coli metabolic) networks, predicting the probability of new links with high precision. The framework that we have developed can thus be used for predicting new links in evolving networks, and provides a different perspective on preferential attachment as an emergent phenomenon.

A molecular model for ice nucleation and growth, attachment 1

NASA Technical Reports Server (NTRS)

Plummer, P. L. M.

1981-01-01

The quantum mechanical technique is used to study ionic, configurational, and impurity defects in the ice surface. In addition to static calculations of the energetics of the water monomer-ice surface interactions, molecular dynamics studies were initiated. The calculations of the monomer-ice surface interaction, molecular dynamics studies were initiated. The calculations of monomer-ice surface interactions indicate that many adsorption sites exist on the ice surfaces and that the barriers between bonding sites are relatively low. Bonding on the prism face of ice is preferentially above lattice sites.

Smoluchowski Equation for Networks: Merger Induced Intermittent Giant Node Formation and Degree Gap

NASA Astrophysics Data System (ADS)

Goto, Hayato; Viegas, Eduardo; Jensen, Henrik Jeldtoft; Takayasu, Hideki; Takayasu, Misako

2018-06-01

The dynamical phase diagram of a network undergoing annihilation, creation, and coagulation of nodes is found to exhibit two regimes controlled by the combined effect of preferential attachment for initiator and target nodes during coagulation and for link assignment to new nodes. The first regime exhibits smooth dynamics and power law degree distributions. In the second regime, giant degree nodes and gaps in the degree distribution are formed intermittently. Data for the Japanese firm network in 1994 and 2014 suggests that this network is moving towards the intermittent switching region.

Mechanisms of complex network growth: Synthesis of the preferential attachment and fitness models

NASA Astrophysics Data System (ADS)

Golosovsky, Michael

2018-06-01

We analyze growth mechanisms of complex networks and focus on their validation by measurements. To this end we consider the equation Δ K =A (t ) (K +K0) Δ t , where K is the node's degree, Δ K is its increment, A (t ) is the aging constant, and K0 is the initial attractivity. This equation has been commonly used to validate the preferential attachment mechanism. We show that this equation is undiscriminating and holds for the fitness model [Caldarelli et al., Phys. Rev. Lett. 89, 258702 (2002), 10.1103/PhysRevLett.89.258702] as well. In other words, accepted method of the validation of the microscopic mechanism of network growth does not discriminate between "rich-gets-richer" and "good-gets-richer" scenarios. This means that the growth mechanism of many natural complex networks can be based on the fitness model rather than on the preferential attachment, as it was believed so far. The fitness model yields the long-sought explanation for the initial attractivity K0, an elusive parameter which was left unexplained within the framework of the preferential attachment model. We show that the initial attractivity is determined by the width of the fitness distribution. We also present the network growth model based on recursive search with memory and show that this model contains both the preferential attachment and the fitness models as extreme cases.

Emergence of Soft Communities from Geometric Preferential Attachment

PubMed Central

Zuev, Konstantin; Boguñá, Marián; Bianconi, Ginestra; Krioukov, Dmitri

2015-01-01

All real networks are different, but many have some structural properties in common. There seems to be no consensus on what the most common properties are, but scale-free degree distributions, strong clustering, and community structure are frequently mentioned without question. Surprisingly, there exists no simple generative mechanism explaining all the three properties at once in growing networks. Here we show how latent network geometry coupled with preferential attachment of nodes to this geometry fills this gap. We call this mechanism geometric preferential attachment (GPA), and validate it against the Internet. GPA gives rise to soft communities that provide a different perspective on the community structure in networks. The connections between GPA and cosmological models, including inflation, are also discussed. PMID:25923110

Wikipedia editing dynamics.

PubMed

Gandica, Y; Carvalho, J; Sampaio Dos Aidos, F

2015-01-01

A model for the probabilistic function followed in editing Wikipedia is presented and compared with simulations and real data. It is argued that the probability of editing is proportional to the editor's number of previous edits (preferential attachment), to the editor's fitness, and to an aging factor. Using these simple ingredients, it is possible to reproduce the results obtained for Wikipedia editing dynamics for a collection of single pages as well as the averaged results. Using a stochastic process framework, a recursive equation was obtained for the average of the number of edits per editor that seems to describe the editing behavior in Wikipedia.

Wikipedia editing dynamics

NASA Astrophysics Data System (ADS)

Gandica, Y.; Carvalho, J.; Sampaio dos Aidos, F.

2015-01-01

A model for the probabilistic function followed in editing Wikipedia is presented and compared with simulations and real data. It is argued that the probability of editing is proportional to the editor's number of previous edits (preferential attachment), to the editor's fitness, and to an aging factor. Using these simple ingredients, it is possible to reproduce the results obtained for Wikipedia editing dynamics for a collection of single pages as well as the averaged results. Using a stochastic process framework, a recursive equation was obtained for the average of the number of edits per editor that seems to describe the editing behavior in Wikipedia.

A Knowledge Generation Model via the Hypernetwork

PubMed Central

Liu, Jian-Guo; Yang, Guang-Yong; Hu, Zhao-Long

2014-01-01

The influence of the statistical properties of the network on the knowledge diffusion has been extensively studied. However, the structure evolution and the knowledge generation processes are always integrated simultaneously. By introducing the Cobb-Douglas production function and treating the knowledge growth as a cooperative production of knowledge, in this paper, we present two knowledge-generation dynamic evolving models based on different evolving mechanisms. The first model, named “HDPH model,” adopts the hyperedge growth and the hyperdegree preferential attachment mechanisms. The second model, named “KSPH model,” adopts the hyperedge growth and the knowledge stock preferential attachment mechanisms. We investigate the effect of the parameters on the total knowledge stock of the two models. The hyperdegree distribution of the HDPH model can be theoretically analyzed by the mean-field theory. The analytic result indicates that the hyperdegree distribution of the HDPH model obeys the power-law distribution and the exponent is . Furthermore, we present the distributions of the knowledge stock for different parameters . The findings indicate that our proposed models could be helpful for deeply understanding the scientific research cooperation. PMID:24626143

A knowledge generation model via the hypernetwork.

PubMed

Liu, Jian-Guo; Yang, Guang-Yong; Hu, Zhao-Long

2014-01-01

The influence of the statistical properties of the network on the knowledge diffusion has been extensively studied. However, the structure evolution and the knowledge generation processes are always integrated simultaneously. By introducing the Cobb-Douglas production function and treating the knowledge growth as a cooperative production of knowledge, in this paper, we present two knowledge-generation dynamic evolving models based on different evolving mechanisms. The first model, named "HDPH model," adopts the hyperedge growth and the hyperdegree preferential attachment mechanisms. The second model, named "KSPH model," adopts the hyperedge growth and the knowledge stock preferential attachment mechanisms. We investigate the effect of the parameters (α,β) on the total knowledge stock of the two models. The hyperdegree distribution of the HDPH model can be theoretically analyzed by the mean-field theory. The analytic result indicates that the hyperdegree distribution of the HDPH model obeys the power-law distribution and the exponent is γ = 2 + 1/m. Furthermore, we present the distributions of the knowledge stock for different parameters (α,β). The findings indicate that our proposed models could be helpful for deeply understanding the scientific research cooperation.

Generating Billion-Edge Scale-Free Networks in Seconds: Performance Study of a Novel GPU-based Preferential Attachment Model

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

Perumalla, Kalyan S.; Alam, Maksudul

A novel parallel algorithm is presented for generating random scale-free networks using the preferential-attachment model. The algorithm, named cuPPA, is custom-designed for single instruction multiple data (SIMD) style of parallel processing supported by modern processors such as graphical processing units (GPUs). To the best of our knowledge, our algorithm is the first to exploit GPUs, and also the fastest implementation available today, to generate scale free networks using the preferential attachment model. A detailed performance study is presented to understand the scalability and runtime characteristics of the cuPPA algorithm. In one of the best cases, when executed on an NVidiamore » GeForce 1080 GPU, cuPPA generates a scale free network of a billion edges in less than 2 seconds.« less

Assortativity and leadership emerge from anti-preferential attachment in heterogeneous networks.

PubMed

Sendiña-Nadal, I; Danziger, M M; Wang, Z; Havlin, S; Boccaletti, S

2016-02-18

Real-world networks have distinct topologies, with marked deviations from purely random networks. Many of them exhibit degree-assortativity, with nodes of similar degree more likely to link to one another. Though microscopic mechanisms have been suggested for the emergence of other topological features, assortativity has proven elusive. Assortativity can be artificially implanted in a network via degree-preserving link permutations, however this destroys the graph's hierarchical clustering and does not correspond to any microscopic mechanism. Here, we propose the first generative model which creates heterogeneous networks with scale-free-like properties in degree and clustering distributions and tunable realistic assortativity. Two distinct populations of nodes are incrementally added to an initial network by selecting a subgraph to connect to at random. One population (the followers) follows preferential attachment, while the other population (the potential leaders) connects via anti-preferential attachment: they link to lower degree nodes when added to the network. By selecting the lower degree nodes, the potential leader nodes maintain high visibility during the growth process, eventually growing into hubs. The evolution of links in Facebook empirically validates the connection between the initial anti-preferential attachment and long term high degree. In this way, our work sheds new light on the structure and evolution of social networks.

Assortativity and leadership emerge from anti-preferential attachment in heterogeneous networks

NASA Astrophysics Data System (ADS)

Sendiña-Nadal, I.; Danziger, M. M.; Wang, Z.; Havlin, S.; Boccaletti, S.

2016-02-01

Real-world networks have distinct topologies, with marked deviations from purely random networks. Many of them exhibit degree-assortativity, with nodes of similar degree more likely to link to one another. Though microscopic mechanisms have been suggested for the emergence of other topological features, assortativity has proven elusive. Assortativity can be artificially implanted in a network via degree-preserving link permutations, however this destroys the graph’s hierarchical clustering and does not correspond to any microscopic mechanism. Here, we propose the first generative model which creates heterogeneous networks with scale-free-like properties in degree and clustering distributions and tunable realistic assortativity. Two distinct populations of nodes are incrementally added to an initial network by selecting a subgraph to connect to at random. One population (the followers) follows preferential attachment, while the other population (the potential leaders) connects via anti-preferential attachment: they link to lower degree nodes when added to the network. By selecting the lower degree nodes, the potential leader nodes maintain high visibility during the growth process, eventually growing into hubs. The evolution of links in Facebook empirically validates the connection between the initial anti-preferential attachment and long term high degree. In this way, our work sheds new light on the structure and evolution of social networks.

Do the rich get richer? An empirical analysis of the Bitcoin transaction network.

PubMed

Kondor, Dániel; Pósfai, Márton; Csabai, István; Vattay, Gábor

2014-01-01

The possibility to analyze everyday monetary transactions is limited by the scarcity of available data, as this kind of information is usually considered highly sensitive. Present econophysics models are usually employed on presumed random networks of interacting agents, and only some macroscopic properties (e.g. the resulting wealth distribution) are compared to real-world data. In this paper, we analyze Bitcoin, which is a novel digital currency system, where the complete list of transactions is publicly available. Using this dataset, we reconstruct the network of transactions and extract the time and amount of each payment. We analyze the structure of the transaction network by measuring network characteristics over time, such as the degree distribution, degree correlations and clustering. We find that linear preferential attachment drives the growth of the network. We also study the dynamics taking place on the transaction network, i.e. the flow of money. We measure temporal patterns and the wealth accumulation. Investigating the microscopic statistics of money movement, we find that sublinear preferential attachment governs the evolution of the wealth distribution. We report a scaling law between the degree and wealth associated to individual nodes.

Do the Rich Get Richer? An Empirical Analysis of the Bitcoin Transaction Network

PubMed Central

Kondor, Dániel; Pósfai, Márton; Csabai, István; Vattay, Gábor

2014-01-01

The possibility to analyze everyday monetary transactions is limited by the scarcity of available data, as this kind of information is usually considered highly sensitive. Present econophysics models are usually employed on presumed random networks of interacting agents, and only some macroscopic properties (e.g. the resulting wealth distribution) are compared to real-world data. In this paper, we analyze Bitcoin, which is a novel digital currency system, where the complete list of transactions is publicly available. Using this dataset, we reconstruct the network of transactions and extract the time and amount of each payment. We analyze the structure of the transaction network by measuring network characteristics over time, such as the degree distribution, degree correlations and clustering. We find that linear preferential attachment drives the growth of the network. We also study the dynamics taking place on the transaction network, i.e. the flow of money. We measure temporal patterns and the wealth accumulation. Investigating the microscopic statistics of money movement, we find that sublinear preferential attachment governs the evolution of the wealth distribution. We report a scaling law between the degree and wealth associated to individual nodes. PMID:24505257

The origin of asymmetric behavior of money flow in the business firm network

NASA Astrophysics Data System (ADS)

Miura, W.; Takayasu, H.; Takayasu, M.

2012-09-01

In the business firm network, the number of in-degrees and out-degrees show the same scale-free property, however, the distribution of authorities and hubs show asymmetric behavior. Here we show the result of an analysis of the two-link structure of the network to find the origin of this asymmetric behavior. We find the tendency for big construction firms intermediating small subcontracting firms to have higher hub degrees. By measuring the strength of preferential attachment rate of new companies, we also find a abnormally strong preferential attachment for which the exponent is 1.4 with respect to out-degree when a new company forms a business partnership with a construction company. We propose a new model that reproduces the asymmetric behavior of the degrees of authorities and hubs by changing the preferential attachment rate between the in-degree and the out-degree in the business firm network.

Scale-free behavior of networks with the copresence of preferential and uniform attachment rules

NASA Astrophysics Data System (ADS)

Pachon, Angelica; Sacerdote, Laura; Yang, Shuyi

2018-05-01

Complex networks in different areas exhibit degree distributions with a heavy upper tail. A preferential attachment mechanism in a growth process produces a graph with this feature. We herein investigate a variant of the simple preferential attachment model, whose modifications are interesting for two main reasons: to analyze more realistic models and to study the robustness of the scale-free behavior of the degree distribution. We introduce and study a model which takes into account two different attachment rules: a preferential attachment mechanism (with probability 1 - p) that stresses the rich get richer system, and a uniform choice (with probability p) for the most recent nodes, i.e. the nodes belonging to a window of size w to the left of the last born node. The latter highlights a trend to select one of the last added nodes when no information is available. The recent nodes can be either a given fixed number or a proportion (αn) of the total number of existing nodes. In the first case, we prove that this model exhibits an asymptotically power-law degree distribution. The same result is then illustrated through simulations in the second case. When the window of recent nodes has a constant size, we herein prove that the presence of the uniform rule delays the starting time from which the asymptotic regime starts to hold. The mean number of nodes of degree k and the asymptotic degree distribution are also determined analytically. Finally, a sensitivity analysis on the parameters of the model is performed.

Social networks dynamics revealed by temporal analysis: An example in a non-human primate (Macaca sylvanus) in "La Forêt des Singes".

PubMed

Sosa, Sebastian; Zhang, Peng; Cabanes, Guénaël

2017-06-01

This study applied a temporal social network analysis model to describe three affiliative social networks (allogrooming, sleep in contact, and triadic interaction) in a non-human primate species, Macaca sylvanus. Three main social mechanisms were examined to determine interactional patterns among group members, namely preferential attachment (i.e., highly connected individuals are more likely to form new connections), triadic closure (new connections occur via previous close connections), and homophily (individuals interact preferably with others with similar attributes). Preferential attachment was only observed for triadic interaction network. Triadic closure was significant in allogrooming and triadic interaction networks. Finally, gender homophily was seasonal for allogrooming and sleep in contact networks, and observed in each period for triadic interaction network. These individual-based behaviors are based on individual reactions, and their analysis can shed light on the formation of the affiliative networks determining ultimate coalition networks, and how these networks may evolve over time. A focus on individual behaviors is necessary for a global interactional approach to understanding social behavior rules and strategies. When combined, these social processes could make animal social networks more resilient, thus enabling them to face drastic environmental changes. This is the first study to pinpoint some of the processes underlying the formation of a social structure in a non-human primate species, and identify common mechanisms with humans. The approach used in this study provides an ideal tool for further research seeking to answer long-standing questions about social network dynamics. © 2017 Wiley Periodicals, Inc.

Social influence on selection behaviour: Distinguishing local- and global-driven preferential attachment

PubMed Central

Pan, Xue; Liu, Kecheng

2017-01-01

Social influence drives human selection behaviours when numerous objects competing for limited attentions, which leads to the ‘rich get richer’ dynamics where popular objects tend to get more attentions. However, evidences have been found that, both the global information of the whole system and the local information among one’s friends have significant influence over the one’s selection. Consequently, a key question raises that, it is the local information or the global information more determinative for one’s selection? Here we compare the local-based influence and global-based influence. We show that, the selection behaviour is mainly driven by the local popularity of the objects while the global popularity plays a supplementary role driving the behaviour only when there is little local information for the user to refer to. Thereby, we propose a network model to describe the mechanism of user-object interaction evolution with social influence, where the users perform either local-driven or global-driven preferential attachments to the objects, i.e., the probability of an objects to be selected by a target user is proportional to either its local popularity or global popularity. The simulation suggests that, about 75% of the attachments should be driven by the local popularity to reproduce the empirical observations. It means that, at least in the studied context where users chose businesses on Yelp, there is a probability of 75% for a user to make a selection according to the local popularity. The proposed model and the numerical findings may shed some light on the study of social influence and evolving social systems. PMID:28406984

Social influence on selection behaviour: Distinguishing local- and global-driven preferential attachment.

PubMed

Pan, Xue; Hou, Lei; Liu, Kecheng

2017-01-01

Social influence drives human selection behaviours when numerous objects competing for limited attentions, which leads to the 'rich get richer' dynamics where popular objects tend to get more attentions. However, evidences have been found that, both the global information of the whole system and the local information among one's friends have significant influence over the one's selection. Consequently, a key question raises that, it is the local information or the global information more determinative for one's selection? Here we compare the local-based influence and global-based influence. We show that, the selection behaviour is mainly driven by the local popularity of the objects while the global popularity plays a supplementary role driving the behaviour only when there is little local information for the user to refer to. Thereby, we propose a network model to describe the mechanism of user-object interaction evolution with social influence, where the users perform either local-driven or global-driven preferential attachments to the objects, i.e., the probability of an objects to be selected by a target user is proportional to either its local popularity or global popularity. The simulation suggests that, about 75% of the attachments should be driven by the local popularity to reproduce the empirical observations. It means that, at least in the studied context where users chose businesses on Yelp, there is a probability of 75% for a user to make a selection according to the local popularity. The proposed model and the numerical findings may shed some light on the study of social influence and evolving social systems.

Shape Memory Polymers Containing Higher Acrylate Content Display Increased Endothelial Cell Attachment

PubMed Central

Govindarajan, Tina; Shandas, Robin

2018-01-01

Shape Memory Polymers (SMPs) are smart materials that can recall their shape upon the application of a stimulus, which makes them appealing materials for a variety of applications, especially in biomedical devices. Most prior SMP research has focused on tuning bulk properties; studying surface effects of SMPs may extend the use of these materials to blood-contacting applications, such as cardiovascular stents, where surfaces that support rapid endothelialization have been correlated to stent success. Here, we evaluate endothelial attachment onto the surfaces of a family of SMPs previously developed in our group that have shown promise for biomedical devices. Nine SMP formulations containing varying amounts of tert-Butyl acrylate (tBA) and Poly(ethylene glycol) dimethacrylate (PEGDMA) were analyzed for endothelial cell attachment. Dynamic mechanical analysis (DMA), contact angle studies, and atomic force microscopy (AFM) were used to verify bulk and surface properties of the SMPs. Human umbilical vein endothelial cell (HUVEC) attachment and viability was verified using fluorescent methods. Endothelial cells preferentially attached to SMPs with higher tBA content, which have rougher, more hydrophobic surfaces. HUVECs also displayed an increased metabolic activity on these high tBA SMPs over the course of the study. This class of SMPs may be promising candidates for next generation blood-contacting devices. PMID:29707382

Growing optimal scale-free networks via likelihood

NASA Astrophysics Data System (ADS)

Small, Michael; Li, Yingying; Stemler, Thomas; Judd, Kevin

2015-04-01

Preferential attachment, by which new nodes attach to existing nodes with probability proportional to the existing nodes' degree, has become the standard growth model for scale-free networks, where the asymptotic probability of a node having degree k is proportional to k-γ. However, the motivation for this model is entirely ad hoc. We use exact likelihood arguments and show that the optimal way to build a scale-free network is to attach most new links to nodes of low degree. Curiously, this leads to a scale-free network with a single dominant hub: a starlike structure we call a superstar network. Asymptotically, the optimal strategy is to attach each new node to one of the nodes of degree k with probability proportional to 1/N +ζ (γ ) (k+1 ) γ (in a N node network): a stronger bias toward high degree nodes than exhibited by standard preferential attachment. Our algorithm generates optimally scale-free networks (the superstar networks) as well as randomly sampling the space of all scale-free networks with a given degree exponent γ . We generate viable realization with finite N for 1 ≪γ <2 as well as γ >2 . We observe an apparently discontinuous transition at γ ≈2 between so-called superstar networks and more treelike realizations. Gradually increasing γ further leads to reemergence of a superstar hub. To quantify these structural features, we derive a new analytic expression for the expected degree exponent of a pure preferential attachment process and introduce alternative measures of network entropy. Our approach is generic and can also be applied to an arbitrary degree distribution.

Dynamic Seeding of Perfusing Human Umbilical Vein Endothelial Cells (HUVECs) onto Dual-Function Cell Adhesion Ligands: Arg-Gly-Asp (RGD)-Streptavidin and Biotinylated Fibronectin

PubMed Central

Anamelechi, Charles C.; Clermont, Edward C.; Novak, Matthew T.; Reichert, William M.

2014-01-01

Surfaces decorated with high affinity ligands can be used to facilitate rapid attachment of endothelial cells; however, standard equilibrium cell detachment studies are poorly suited for assessing these initial adhesion events. Here, a dynamic seeding and cell retention method was used to examine the initial attachment of perfusing human umbilical vein endothelial cells (HUVECs) to bare Teflon-AF substrates, substrates pre-adsorbed with fibronectin alone, or substrates co-pre-adsorbed with two dual-function cell-adhesion ligands: biotinylated fibronectin (bFN) and RGD-streptavidin mutant (RGD-SA). Cell attachment was evaluated as a function of cell trypsinization (integrin digestion), surface protein formulation, and cell perfusion rate. Surfaces co-pre-adsorbed with bFN and RGD-SA showed the highest density of attached cells after 8 min of perfusion and the highest percent retention when subjected to shear flow at 60 dynes/cm2 for 2 min. Surfaces with no ligand treatment showed the lowest cell attachment and retention under flow in all cases. HUVECs trypsinized with mild 0.025% trypsin/ethylenediaminetetraacetic acid (EDTA) showed greater cell adhesion after perfusion and higher percent retention after shear flow than those trypsinized using harsher 0.05% trypsin/EDTA. The preferential affinities of the two dual-function ligands for α5β1 and αvβ3 integrins were also examined by surface plasmon resonance (SPR) spectroscopy. The dynamic cell seeding studies confirmed that the dual-function ligand system promotes HUVEC adhesion and retention at short time points when tested using a perfusion assay. SPR studies showed that the two ligands exhibited equal affinity for both α5β1 and αvβ3 integrins but that the combined ligands bound more total integrins than the two ligands tested separately. PMID:19348476

Conflict and convention in dynamic networks.

PubMed

Foley, Michael; Forber, Patrick; Smead, Rory; Riedl, Christoph

2018-03-01

An important way to resolve games of conflict (snowdrift, hawk-dove, chicken) involves adopting a convention: a correlated equilibrium that avoids any conflict between aggressive strategies. Dynamic networks allow individuals to resolve conflict via their network connections rather than changing their strategy. Exploring how behavioural strategies coevolve with social networks reveals new dynamics that can help explain the origins and robustness of conventions. Here, we model the emergence of conventions as correlated equilibria in dynamic networks. Our results show that networks have the tendency to break the symmetry between the two conventional solutions in a strongly biased way. Rather than the correlated equilibrium associated with ownership norms (play aggressive at home, not away), we usually see the opposite host-guest norm (play aggressive away, not at home) evolve on dynamic networks, a phenomenon common to human interaction. We also show that learning to avoid conflict can produce realistic network structures in a way different than preferential attachment models. © 2017 The Author(s).

Dynamics of epidemic diseases on a growing adaptive network

PubMed Central

Demirel, Güven; Barter, Edmund; Gross, Thilo

2017-01-01

The study of epidemics on static networks has revealed important effects on disease prevalence of network topological features such as the variance of the degree distribution, i.e. the distribution of the number of neighbors of nodes, and the maximum degree. Here, we analyze an adaptive network where the degree distribution is not independent of epidemics but is shaped through disease-induced dynamics and mortality in a complex interplay. We study the dynamics of a network that grows according to a preferential attachment rule, while nodes are simultaneously removed from the network due to disease-induced mortality. We investigate the prevalence of the disease using individual-based simulations and a heterogeneous node approximation. Our results suggest that in this system in the thermodynamic limit no epidemic thresholds exist, while the interplay between network growth and epidemic spreading leads to exponential networks for any finite rate of infectiousness when the disease persists. PMID:28186146

Dynamics of epidemic diseases on a growing adaptive network.

PubMed

Demirel, Güven; Barter, Edmund; Gross, Thilo

2017-02-10

The study of epidemics on static networks has revealed important effects on disease prevalence of network topological features such as the variance of the degree distribution, i.e. the distribution of the number of neighbors of nodes, and the maximum degree. Here, we analyze an adaptive network where the degree distribution is not independent of epidemics but is shaped through disease-induced dynamics and mortality in a complex interplay. We study the dynamics of a network that grows according to a preferential attachment rule, while nodes are simultaneously removed from the network due to disease-induced mortality. We investigate the prevalence of the disease using individual-based simulations and a heterogeneous node approximation. Our results suggest that in this system in the thermodynamic limit no epidemic thresholds exist, while the interplay between network growth and epidemic spreading leads to exponential networks for any finite rate of infectiousness when the disease persists.

Dynamics of epidemic diseases on a growing adaptive network

NASA Astrophysics Data System (ADS)

Demirel, Güven; Barter, Edmund; Gross, Thilo

2017-02-01

The study of epidemics on static networks has revealed important effects on disease prevalence of network topological features such as the variance of the degree distribution, i.e. the distribution of the number of neighbors of nodes, and the maximum degree. Here, we analyze an adaptive network where the degree distribution is not independent of epidemics but is shaped through disease-induced dynamics and mortality in a complex interplay. We study the dynamics of a network that grows according to a preferential attachment rule, while nodes are simultaneously removed from the network due to disease-induced mortality. We investigate the prevalence of the disease using individual-based simulations and a heterogeneous node approximation. Our results suggest that in this system in the thermodynamic limit no epidemic thresholds exist, while the interplay between network growth and epidemic spreading leads to exponential networks for any finite rate of infectiousness when the disease persists.

Relating Topological Determinants of Complex Networks to Their Spectral Properties: Structural and Dynamical Effects

NASA Astrophysics Data System (ADS)

Castellano, Claudio; Pastor-Satorras, Romualdo

2017-10-01

The largest eigenvalue of a network's adjacency matrix and its associated principal eigenvector are key elements for determining the topological structure and the properties of dynamical processes mediated by it. We present a physically grounded expression relating the value of the largest eigenvalue of a given network to the largest eigenvalue of two network subgraphs, considered as isolated: the hub with its immediate neighbors and the densely connected set of nodes with maximum K -core index. We validate this formula by showing that it predicts, with good accuracy, the largest eigenvalue of a large set of synthetic and real-world topologies. We also present evidence of the consequences of these findings for broad classes of dynamics taking place on the networks. As a by-product, we reveal that the spectral properties of heterogeneous networks built according to the linear preferential attachment model are qualitatively different from those of their static counterparts.

Simulating adverse event spontaneous reporting systems as preferential attachment networks: application to the Vaccine Adverse Event Reporting System.

PubMed

Scott, J; Botsis, T; Ball, R

2014-01-01

Spontaneous Reporting Systems [SRS] are critical tools in the post-licensure evaluation of medical product safety. Regulatory authorities use a variety of data mining techniques to detect potential safety signals in SRS databases. Assessing the performance of such signal detection procedures requires simulated SRS databases, but simulation strategies proposed to date each have limitations. We sought to develop a novel SRS simulation strategy based on plausible mechanisms for the growth of databases over time. We developed a simulation strategy based on the network principle of preferential attachment. We demonstrated how this strategy can be used to create simulations based on specific databases of interest, and provided an example of using such simulations to compare signal detection thresholds for a popular data mining algorithm. The preferential attachment simulations were generally structurally similar to our targeted SRS database, although they had fewer nodes of very high degree. The approach was able to generate signal-free SRS simulations, as well as mimicking specific known true signals. Explorations of different reporting thresholds for the FDA Vaccine Adverse Event Reporting System suggested that using proportional reporting ratio [PRR] > 3.0 may yield better signal detection operating characteristics than the more commonly used PRR > 2.0 threshold. The network analytic approach to SRS simulation based on the principle of preferential attachment provides an attractive framework for exploring the performance of safety signal detection algorithms. This approach is potentially more principled and versatile than existing simulation approaches. The utility of network-based SRS simulations needs to be further explored by evaluating other types of simulated signals with a broader range of data mining approaches, and comparing network-based simulations with other simulation strategies where applicable.

Submicron structures provide preferential spots for carbon and nitrogen sequestration in soils

PubMed Central

Vogel, Cordula; Mueller, Carsten W.; Höschen, Carmen; Buegger, Franz; Heister, Katja; Schulz, Stefanie; Schloter, Michael; Kögel-Knabner, Ingrid

2014-01-01

The sequestration of carbon and nitrogen by clay-sized particles in soils is well established, and clay content or mineral surface area has been used to estimate the sequestration potential of soils. Here, via incubation of a sieved (<2 mm) topsoil with labelled litter, we find that only some of the clay-sized surfaces bind organic matter (OM). Surprisingly, <19% of the visible mineral areas show an OM attachment. OM is preferentially associated with organo-mineral clusters with rough surfaces. By combining nano-scale secondary ion mass spectrometry and isotopic tracing, we distinguish between new labelled and pre-existing OM and show that new OM is preferentially attached to already present organo-mineral clusters. These results, which provide evidence that only a limited proportion of the clay-sized surfaces contribute to OM sequestration, revolutionize our view of carbon sequestration in soils and the widely used carbon saturation estimates. PMID:24399306

Crossover transition in the fluctuation of Internet

NASA Astrophysics Data System (ADS)

Qian, Jiang-Hai

2018-06-01

The inconsistent fluctuation behavior of Internet predicted by preferential attachment(PA) and Gibrat's law requires empirical investigations on the actual system. By using the interval-tunable Gibrat's law statistics, we find the actual fluctuation, characterized by the conditional standard deviation of the degree growth rate, changes with the interval length and displays a crossover transition from PA type to Gibrat's law type, which has not yet been captured by any previous models. We characterize the transition dynamics quantitatively and determine the applicative range of PA and Gibrat's law. The correlation analysis indicates the crossover transition may be attributed to the accumulative correlation between the internal links.

Quantifying attachment and antibiotic resistance of Escherichia coli from conventional and organic swine manure

USDA-ARS?s Scientific Manuscript database

Broad spectrum antibiotics, used to treat infections in livestock, are often administered at sub-therapeutic levels in feed rations to promote growth and for prophylaxis. Previous studies have shown that bacteria preferentially attach to sediments affecting their transport in overland flow; however...

Fame and obsolescence: Disentangling growth and aging dynamics of patent citations.

PubMed

Higham, K W; Governale, M; Jaffe, A B; Zülicke, U

2017-04-01

We present an analysis of citations accrued over time by patents granted by the United States Patent and Trademark Office in 1998. In contrast to previous studies, a disaggregation by technology category is performed, and exogenously caused citation-number growth is controlled for. Our approach reveals an intrinsic citation rate that clearly separates into an-in the long run, exponentially time-dependent-aging function and a completely time-independent preferential-attachment-type growth kernel. For the general case of such a separable citation rate, we obtain the time-dependent citation distribution analytically in a form that is valid for any functional form of its aging and growth parts. Good agreement between theory and long-time characteristics of patent-citation data establishes our work as a useful framework for addressing still open questions about knowledge-propagation dynamics, such as the observed excess of citations at short times.

Fame and obsolescence: Disentangling growth and aging dynamics of patent citations

NASA Astrophysics Data System (ADS)

Higham, K. W.; Governale, M.; Jaffe, A. B.; Zülicke, U.

2017-04-01

We present an analysis of citations accrued over time by patents granted by the United States Patent and Trademark Office in 1998. In contrast to previous studies, a disaggregation by technology category is performed, and exogenously caused citation-number growth is controlled for. Our approach reveals an intrinsic citation rate that clearly separates into an—in the long run, exponentially time-dependent—aging function and a completely time-independent preferential-attachment-type growth kernel. For the general case of such a separable citation rate, we obtain the time-dependent citation distribution analytically in a form that is valid for any functional form of its aging and growth parts. Good agreement between theory and long-time characteristics of patent-citation data establishes our work as a useful framework for addressing still open questions about knowledge-propagation dynamics, such as the observed excess of citations at short times.

The Role of Temporal Trends in Growing Networks

PubMed Central

Ruppin, Eytan; Shavitt, Yuval

2016-01-01

The rich get richer principle, manifested by the Preferential attachment (PA) mechanism, is widely considered one of the major factors in the growth of real-world networks. PA stipulates that popular nodes are bound to be more attractive than less popular nodes; for example, highly cited papers are more likely to garner further citations. However, it overlooks the transient nature of popularity, which is often governed by trends. Here, we show that in a wide range of real-world networks the recent popularity of a node, i.e., the extent by which it accumulated links recently, significantly influences its attractiveness and ability to accumulate further links. We proceed to model this observation with a natural extension to PA, named Trending Preferential Attachment (TPA), in which edges become less influential as they age. TPA quantitatively parametrizes a fundamental network property, namely the network’s tendency to trends. Through TPA, we find that real-world networks tend to be moderately to highly trendy. Networks are characterized by different susceptibilities to trends, which determine their structure to a large extent. Trendy networks display complex structural traits, such as modular community structure and degree-assortativity, occurring regularly in real-world networks. In summary, this work addresses an inherent trait of complex networks, which greatly affects their growth and structure, and develops a unified model to address its interaction with preferential attachment. PMID:27486847

Effect of homophily on network formation

NASA Astrophysics Data System (ADS)

Kim, Kibae; Altmann, Jörn

2017-03-01

Although there is much research on network formation based on the preferential attachment rule, the research did not come up with a formula that, on the one hand, can reproduce shapes of cumulative degree distributions of empirical complex networks and, on the other hand, can represent intuitively theories on individual behavior. In this paper, we propose a formula that closes this gap by integrating into the formula for the preferential attachment rule (i.e., a node with higher degree is more likely to gain a new link) a representation of the theory of individual behavior with respect to nodes preferring to connect to other nodes with similar attributes (i.e., homophily). Based on this formula, we simulate the shapes of cumulative degree distributions for different levels of homophily and five different seed networks. Our simulation results suggest that homophily and the preferential attachment rule interact for all five types of seed networks. Surprisingly, the resulting cumulative degree distribution in log-log scale always shifts from a concave shape to a convex shape, as the level of homophily gets larger. Therefore, our formula can explain intuitively why some of the empirical complex networks show a linear cumulative degree distribution in log-log scale while others show either a concave or convex shape. Furthermore, another major finding indicates that homophily makes people of a group richer than people outside this group, which is a surprising and significant finding.

The value of less connected agents in Boolean networks

NASA Astrophysics Data System (ADS)

Epstein, Daniel; Bazzan, Ana L. C.

2013-11-01

In multiagent systems, agents often face binary decisions where one seeks to take either the minority or the majority side. Examples are minority and congestion games in general, i.e., situations that require coordination among the agents in order to depict efficient decisions. In minority games such as the El Farol Bar Problem, previous works have shown that agents may reach appropriate levels of coordination, mostly by looking at the history of past decisions. Not many works consider any kind of structure of the social network, i.e., how agents are connected. Moreover, when structure is indeed considered, it assumes some kind of random network with a given, fixed connectivity degree. The present paper departs from the conventional approach in some ways. First, it considers more realistic network topologies, based on preferential attachments. This is especially useful in social networks. Second, the formalism of random Boolean networks is used to help agents to make decisions given their attachments (for example acquaintances). This is coupled with a reinforcement learning mechanism that allows agents to select strategies that are locally and globally efficient. Third, we use agent-based modeling and simulation, a microscopic approach, which allows us to draw conclusions about individuals and/or classes of individuals. Finally, for the sake of illustration we use two different scenarios, namely the El Farol Bar Problem and a binary route choice scenario. With this approach we target systems that adapt dynamically to changes in the environment, including other adaptive decision-makers. Our results using preferential attachments and random Boolean networks are threefold. First we show that an efficient equilibrium can be achieved, provided agents do experimentation. Second, microscopic analysis show that influential agents tend to consider few inputs in their Boolean functions. Third, we have also conducted measurements related to network clustering and centrality that help to see how agents are organized.

Preferential adhesion of surface groups of Bacillus subtilis on gibbsite at different ionic strengths and pHs revealed by ATR-FTIR spectroscopy.

PubMed

Hong, Zhi-Neng; Jiang, Jun; Li, Jiu-Yu; Xu, Ren-Kou

2018-05-01

Adhesion of bacteria onto minerals is a ubiquitous process that plays a central role in many biogeochemical, microbiology and environmental processes in soil and sediment. Although bacterial adhesion onto soil minerals such as phyllosilicates and Fe-oxides have been investigated extensively, little is known about the mechanisms for bacterial attachment onto Al-oxides. Here, we explored the adhesion of Bacillus subtilis onto gibbsite (γ-AlOOH) under various ionic strengths (1, 10, 50, and 100 mM NaCl) and pHs (pH 4, 7, and 9) by in-situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The time evolution of the peak intensities of the attached bacteria suggested that the adhesion underwent an initial rapid reaction followed by a slow pseudo-first-order kinetic stage. Spectral comparison between the attached and free cells, together with the interaction energy calculated with the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory and the micro-morphology of bacteria-gibbsite complexes, indicated that both electrostatic and chemical (bacterial groups such as phosphate and carboxyl covalently bind to gibbsite) interactions participated in the adhesion processes. Both solution ionic strength (IS) and pH impacted the spectra of attached bacteria, but the peak intensity of different bands changed differently with these two factors, showing a preferential adhesion of surface groups (phosphate, carboxyl, and amide groups) on gibbsite at different conditions. The diverse responses to IS and pH alteration of the forces (chemical bonds, electrostatic attractions, and the hydrophobic interactions) that essentially govern the adhesion might be responsible for the preferential adhesion. These results may help to better understand how bacteria adhere onto soil oxides at molecular scales. Copyright © 2018 Elsevier B.V. All rights reserved.

Adsorption and decontamination of α-synuclein from medically and environmentally-relevant surfaces.

PubMed

Phan, Hanh T M; Bartz, Jason C; Ayers, Jacob; Giasson, Benoit I; Schubert, Mathias; Rodenhausen, Keith B; Kananizadeh, Negin; Li, Yusong; Bartelt-Hunt, Shannon L

2018-06-01

The assembly and accumulation of α-synuclein fibrils are implicated in the development of several neurodegenerative disorders including multiple system atrophy and Parkinson's disease. Pre-existing α-synuclein fibrils can recruit and convert soluble non-fibrillar α-synuclein to the fibrillar form similar to what is observed in prion diseases. This raises concerns regarding attachment of fibrillary α-synuclein to medical instruments and subsequent exposure of patients to α-synuclein similar to what has been observed in iatrogenic transmission of prions. Here, we evaluated adsorption and desorption of α-synuclein to two surfaces: stainless steel and a gold surface coated with a 11-Amino-1-undecanethiol hydrochloride self-assembled-monolayer (SAM) using in-situ combinatorial quartz crystal microbalance with dissipation and spectroscopic ellipsometry. α-Synuclein was found to attach to both surfaces, however, increased α-synuclein adsorption was observed onto the positively charged SAM surface compared to the stainless steel surface. Dynamic light scattering data showed that larger α-synuclein fibrils were preferentially attached to the stainless steel surface when compared with the distributions in the original α-synuclein solution and on the SAM surface. We determined that after attachment, introduction of a 1N NaOH solution could completely remove α-synuclein adsorbed on the stainless steel surface while α-synuclein was retained on the SAM surface. Our results indicate α-synuclein can bind to multiple surface types and that decontamination is surface-dependent. Copyright © 2018 Elsevier B.V. All rights reserved.

Preferential attachment in multiple trade networks

NASA Astrophysics Data System (ADS)

Foschi, Rachele; Riccaboni, Massimo; Schiavo, Stefano

2014-08-01

In this paper we develop a model for the evolution of multiple networks which is able to replicate the concentrated and sparse nature of world trade data. Our model is an extension of the preferential attachment growth model to the case of multiple networks. Countries trade a variety of goods of different complexity. Every country progressively evolves from trading less sophisticated to high-tech goods. The probabilities of capturing more trade opportunities at a given level of complexity and of starting to trade more complex goods are both proportional to the number of existing trade links. We provide a set of theoretical predictions and simulative results. A calibration exercise shows that our model replicates the same concentration level of world trade as well as the sparsity pattern of the trade matrix. We also discuss a set of numerical solutions to deal with large multiple networks.

Spreading dynamics of an e-commerce preferential information model on scale-free networks

NASA Astrophysics Data System (ADS)

Wan, Chen; Li, Tao; Guan, Zhi-Hong; Wang, Yuanmei; Liu, Xiongding

2017-02-01

In order to study the influence of the preferential degree and the heterogeneity of underlying networks on the spread of preferential e-commerce information, we propose a novel susceptible-infected-beneficial model based on scale-free networks. The spreading dynamics of the preferential information are analyzed in detail using the mean-field theory. We determine the basic reproductive number and equilibria. The theoretical analysis indicates that the basic reproductive number depends mainly on the preferential degree and the topology of the underlying networks. We prove the global stability of the information-elimination equilibrium. The permanence of preferential information and the global attractivity of the information-prevailing equilibrium are also studied in detail. Some numerical simulations are presented to verify the theoretical results.

Functional complexity emerging from anatomical constraints in the brain: the significance of network modularity and rich-clubs

NASA Astrophysics Data System (ADS)

Zamora-López, Gorka; Chen, Yuhan; Deco, Gustavo; Kringelbach, Morten L.; Zhou, Changsong

2016-12-01

The large-scale structural ingredients of the brain and neural connectomes have been identified in recent years. These are, similar to the features found in many other real networks: the arrangement of brain regions into modules and the presence of highly connected regions (hubs) forming rich-clubs. Here, we examine how modules and hubs shape the collective dynamics on networks and we find that both ingredients lead to the emergence of complex dynamics. Comparing the connectomes of C. elegans, cats, macaques and humans to surrogate networks in which either modules or hubs are destroyed, we find that functional complexity always decreases in the perturbed networks. A comparison between simulated and empirically obtained resting-state functional connectivity indicates that the human brain, at rest, lies in a dynamical state that reflects the largest complexity its anatomical connectome can host. Last, we generalise the topology of neural connectomes into a new hierarchical network model that successfully combines modular organisation with rich-club forming hubs. This is achieved by centralising the cross-modular connections through a preferential attachment rule. Our network model hosts more complex dynamics than other hierarchical models widely used as benchmarks.

Functional complexity emerging from anatomical constraints in the brain: the significance of network modularity and rich-clubs

PubMed Central

Zamora-López, Gorka; Chen, Yuhan; Deco, Gustavo; Kringelbach, Morten L.; Zhou, Changsong

2016-01-01

The large-scale structural ingredients of the brain and neural connectomes have been identified in recent years. These are, similar to the features found in many other real networks: the arrangement of brain regions into modules and the presence of highly connected regions (hubs) forming rich-clubs. Here, we examine how modules and hubs shape the collective dynamics on networks and we find that both ingredients lead to the emergence of complex dynamics. Comparing the connectomes of C. elegans, cats, macaques and humans to surrogate networks in which either modules or hubs are destroyed, we find that functional complexity always decreases in the perturbed networks. A comparison between simulated and empirically obtained resting-state functional connectivity indicates that the human brain, at rest, lies in a dynamical state that reflects the largest complexity its anatomical connectome can host. Last, we generalise the topology of neural connectomes into a new hierarchical network model that successfully combines modular organisation with rich-club forming hubs. This is achieved by centralising the cross-modular connections through a preferential attachment rule. Our network model hosts more complex dynamics than other hierarchical models widely used as benchmarks. PMID:27917958

Quantification and Control of Wall Effects in Porous Media Experiments

NASA Astrophysics Data System (ADS)

Roth, E. J.; Mays, D. C.; Neupauer, R.; Crimaldi, J. P.

2017-12-01

Fluid flow dynamics in porous media are dominated by media heterogeneity. This heterogeneity can create preferential pathways in which local seepage velocities dwarf system seepage velocities, further complicating an already incomplete understanding of dispersive processes. In physical models of porous media flows, apparatus walls introduce preferential flow paths (i.e., wall effects) that may overwhelm other naturally occurring preferential pathways within the apparatus, leading to deceptive results. We used planar laser-induced fluorescence (PLIF) in conjunction with refractive index matched (RIM) porous media and pore fluid to observe fluid dynamics in the porous media, with particular attention to the region near the apparatus walls in a 17 cm x 8 cm x 7 cm uniform flow cell. Hexagonal close packed spheres were used to create an isotropic, homogenous porous media field in the interior of the apparatus. Visualization of the movement of a fluorescent dye revealed the influence of the wall in creating higher permeability preferential flow paths in an otherwise homogenous media packing. These preferential flow paths extended approximately one half of one sphere diameter from the wall for homogenously packed regions, with a quickly diminishing effect on flow dynamics for homogenous media adjacent to the preferential pathway, but with major influence on flow dynamics for adjoining heterogeneous regions. Multiple approaches to mitigate wall effects were investigated, and a modified wall was created such that the fluid dynamics near the wall mimics the fluid dynamics within the homogenous porous media. This research supports the design of a two-dimensional experimental apparatus that will simulate engineered pumping schemes for use in contaminant remediation. However, this research could benefit the design of fixed bed reactors or other engineering challenges in which vessel walls contribute to unwanted preferential flow.

Complex networks as an emerging property of hierarchical preferential attachment.

PubMed

Hébert-Dufresne, Laurent; Laurence, Edward; Allard, Antoine; Young, Jean-Gabriel; Dubé, Louis J

2015-12-01

Real complex systems are not rigidly structured; no clear rules or blueprints exist for their construction. Yet, amidst their apparent randomness, complex structural properties universally emerge. We propose that an important class of complex systems can be modeled as an organization of many embedded levels (potentially infinite in number), all of them following the same universal growth principle known as preferential attachment. We give examples of such hierarchy in real systems, for instance, in the pyramid of production entities of the film industry. More importantly, we show how real complex networks can be interpreted as a projection of our model, from which their scale independence, their clustering, their hierarchy, their fractality, and their navigability naturally emerge. Our results suggest that complex networks, viewed as growing systems, can be quite simple, and that the apparent complexity of their structure is largely a reflection of their unobserved hierarchical nature.

Complex networks as an emerging property of hierarchical preferential attachment

NASA Astrophysics Data System (ADS)

Hébert-Dufresne, Laurent; Laurence, Edward; Allard, Antoine; Young, Jean-Gabriel; Dubé, Louis J.

2015-12-01

Real complex systems are not rigidly structured; no clear rules or blueprints exist for their construction. Yet, amidst their apparent randomness, complex structural properties universally emerge. We propose that an important class of complex systems can be modeled as an organization of many embedded levels (potentially infinite in number), all of them following the same universal growth principle known as preferential attachment. We give examples of such hierarchy in real systems, for instance, in the pyramid of production entities of the film industry. More importantly, we show how real complex networks can be interpreted as a projection of our model, from which their scale independence, their clustering, their hierarchy, their fractality, and their navigability naturally emerge. Our results suggest that complex networks, viewed as growing systems, can be quite simple, and that the apparent complexity of their structure is largely a reflection of their unobserved hierarchical nature.

Features and heterogeneities in growing network models

NASA Astrophysics Data System (ADS)

Ferretti, Luca; Cortelezzi, Michele; Yang, Bin; Marmorini, Giacomo; Bianconi, Ginestra

2012-06-01

Many complex networks from the World Wide Web to biological networks grow taking into account the heterogeneous features of the nodes. The feature of a node might be a discrete quantity such as a classification of a URL document such as personal page, thematic website, news, blog, search engine, social network, etc., or the classification of a gene in a functional module. Moreover the feature of a node can be a continuous variable such as the position of a node in the embedding space. In order to account for these properties, in this paper we provide a generalization of growing network models with preferential attachment that includes the effect of heterogeneous features of the nodes. The main effect of heterogeneity is the emergence of an “effective fitness” for each class of nodes, determining the rate at which nodes acquire new links. The degree distribution exhibits a multiscaling behavior analogous to the the fitness model. This property is robust with respect to variations in the model, as long as links are assigned through effective preferential attachment. Beyond the degree distribution, in this paper we give a full characterization of the other relevant properties of the model. We evaluate the clustering coefficient and show that it disappears for large network size, a property shared with the Barabási-Albert model. Negative degree correlations are also present in this class of models, along with nontrivial mixing patterns among features. We therefore conclude that both small clustering coefficients and disassortative mixing are outcomes of the preferential attachment mechanism in general growing networks.

Attachment site recognition and regulation of directionality by the serine integrases

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

Rutherford, Karen; Yuan, Peng; Perry, Kay

Serine integrases catalyze the integration of bacteriophage DNA into a host genome by site-specific recombination between ‘attachment sites’ in the phage ( attP ) and the host ( attB ). The reaction is highly directional; the reverse excision reaction between the product attL and attR sites does not occur in the absence of a phage-encoded factor, nor does recombination occur between other pairings of attachment sites. A mechanistic understanding of how these enzymes achieve site-selectivity and directionality has been limited by a lack of structural models. Here, we report the structure of the C-terminal domains of a serine integrase boundmore » to an attP DNA half-site. The structure leads directly to models for understanding how the integrase-bound attP and attB sites differ, why these enzymes preferentially form attP × attB synaptic complexes to initiate recombination, and how attL × attR recombination is prevented. In these models, different domain organizations on attP vs. attB half-sites allow attachment-site specific interactions to form between integrase subunits via an unusual protruding coiled-coil motif. These interactions are used to preferentially synapse integrase-bound attP and attB and inhibit synapsis of integrase-bound attL and attR . The results provide a structural framework for understanding, testing and engineering serine integrase function.« less

Network geometry with flavor: From complexity to quantum geometry

NASA Astrophysics Data System (ADS)

Bianconi, Ginestra; Rahmede, Christoph

2016-03-01

Network geometry is attracting increasing attention because it has a wide range of applications, ranging from data mining to routing protocols in the Internet. At the same time advances in the understanding of the geometrical properties of networks are essential for further progress in quantum gravity. In network geometry, simplicial complexes describing the interaction between two or more nodes play a special role. In fact these structures can be used to discretize a geometrical d -dimensional space, and for this reason they have already been widely used in quantum gravity. Here we introduce the network geometry with flavor s =-1 ,0 ,1 (NGF) describing simplicial complexes defined in arbitrary dimension d and evolving by a nonequilibrium dynamics. The NGF can generate discrete geometries of different natures, ranging from chains and higher-dimensional manifolds to scale-free networks with small-world properties, scale-free degree distribution, and nontrivial community structure. The NGF admits as limiting cases both the Bianconi-Barabási models for complex networks, the stochastic Apollonian network, and the recently introduced model for complex quantum network manifolds. The thermodynamic properties of NGF reveal that NGF obeys a generalized area law opening a new scenario for formulating its coarse-grained limit. The structure of NGF is strongly dependent on the dimensionality d . In d =1 NGFs grow complex networks for which the preferential attachment mechanism is necessary in order to obtain a scale-free degree distribution. Instead, for NGF with dimension d >1 it is not necessary to have an explicit preferential attachment rule to generate scale-free topologies. We also show that NGF admits a quantum mechanical description in terms of associated quantum network states. Quantum network states evolve by a Markovian dynamics and a quantum network state at time t encodes all possible NGF evolutions up to time t . Interestingly the NGF remains fully classical but its statistical properties reveal the relation to its quantum mechanical description. In fact the δ -dimensional faces of the NGF have generalized degrees that follow either the Fermi-Dirac, Boltzmann, or Bose-Einstein statistics depending on the flavor s and the dimensions d and δ .

Network geometry with flavor: From complexity to quantum geometry.

PubMed

Bianconi, Ginestra; Rahmede, Christoph

2016-03-01

Network geometry is attracting increasing attention because it has a wide range of applications, ranging from data mining to routing protocols in the Internet. At the same time advances in the understanding of the geometrical properties of networks are essential for further progress in quantum gravity. In network geometry, simplicial complexes describing the interaction between two or more nodes play a special role. In fact these structures can be used to discretize a geometrical d-dimensional space, and for this reason they have already been widely used in quantum gravity. Here we introduce the network geometry with flavor s=-1,0,1 (NGF) describing simplicial complexes defined in arbitrary dimension d and evolving by a nonequilibrium dynamics. The NGF can generate discrete geometries of different natures, ranging from chains and higher-dimensional manifolds to scale-free networks with small-world properties, scale-free degree distribution, and nontrivial community structure. The NGF admits as limiting cases both the Bianconi-Barabási models for complex networks, the stochastic Apollonian network, and the recently introduced model for complex quantum network manifolds. The thermodynamic properties of NGF reveal that NGF obeys a generalized area law opening a new scenario for formulating its coarse-grained limit. The structure of NGF is strongly dependent on the dimensionality d. In d=1 NGFs grow complex networks for which the preferential attachment mechanism is necessary in order to obtain a scale-free degree distribution. Instead, for NGF with dimension d>1 it is not necessary to have an explicit preferential attachment rule to generate scale-free topologies. We also show that NGF admits a quantum mechanical description in terms of associated quantum network states. Quantum network states evolve by a Markovian dynamics and a quantum network state at time t encodes all possible NGF evolutions up to time t. Interestingly the NGF remains fully classical but its statistical properties reveal the relation to its quantum mechanical description. In fact the δ-dimensional faces of the NGF have generalized degrees that follow either the Fermi-Dirac, Boltzmann, or Bose-Einstein statistics depending on the flavor s and the dimensions d and δ.

Age structure and cooperation in coevolutionary games on dynamic network

NASA Astrophysics Data System (ADS)

Qin, Zilong; Hu, Zhenhua; Zhou, Xiaoping; Yi, Jingzhang

2015-04-01

Our proposed model imitates the growth of a population and describes the age structure and the level of cooperation in games on dynamic network with continuous changes of structure and topology. The removal of nodes and links caused by age-dependent attack, together with the nodes addition standing for the newborns of population, badly ruins Matthew effect in this coevolutionary process. Though the network is generated by growth and preferential attachment, it degenerates into random network and it is no longer heterogeneous. When the removal of nodes and links is equal to the addition of nodes and links, the size of dynamic network is maintained in steady-state, so is the low level of cooperation. Severe structure variation, homogeneous topology and continuous invasion of new defection jointly make dynamic network unsuitable for the survival of cooperator even when the probability with which the newborn players initially adopt the strategy cooperation is high, while things change slightly when the connections of newborn players are restricted. Fortunately, moderate interactions in a generation trigger an optimal recovering process to encourage cooperation. The model developed in this paper outlines an explanation of the cohesion changes in the development process of an organization. Some suggestions for cooperative behavior improvement are given in the end.

Effect of Micro- and Nanoscale Topography on the Adhesion of Bacterial Cells to Solid Surfaces

PubMed Central

Hsu, Lillian C.; Fang, Jean; Borca-Tasciuc, Diana A.; Worobo, Randy W.

2013-01-01

Attachment and biofilm formation by bacterial pathogens on surfaces in natural, industrial, and hospital settings lead to infections and illnesses and even death. Minimizing bacterial attachment to surfaces using controlled topography could reduce the spreading of pathogens and, thus, the incidence of illnesses and subsequent human and financial losses. In this context, the attachment of key microorganisms, including Escherichia coli, Listeria innocua, and Pseudomonas fluorescens, to silica and alumina surfaces with micron and nanoscale topography was investigated. The results suggest that orientation of the attached cells occurs preferentially such as to maximize their contact area with the surface. Moreover, the bacterial cells exhibited different morphologies, including different number and size of cellular appendages, depending on the topographical details of the surface to which they attached. This suggests that bacteria may utilize different mechanisms of attachment in response to surface topography. These results are important for the design of novel microbe-repellant materials. PMID:23416997

A generalized preferential attachment model for business firms growth rates. II. Mathematical treatment

NASA Astrophysics Data System (ADS)

Buldyrev, S. V.; Pammolli, F.; Riccaboni, M.; Yamasaki, K.; Fu, D.-F.; Matia, K.; Stanley, H. E.

2007-05-01

We present a preferential attachment growth model to obtain the distribution P(K) of number of units K in the classes which may represent business firms or other socio-economic entities. We found that P(K) is described in its central part by a power law with an exponent ϕ = 2+b/(1-b) which depends on the probability of entry of new classes, b. In a particular problem of city population this distribution is equivalent to the well known Zipf law. In the absence of the new classes entry, the distribution P(K) is exponential. Using analytical form of P(K) and assuming proportional growth for units, we derive P(g), the distribution of business firm growth rates. The model predicts that P(g) has a Laplacian cusp in the central part and asymptotic power-law tails with an exponent ζ = 3. We test the analytical expressions derived using heuristic arguments by simulations. The model might also explain the size-variance relationship of the firm growth rates.

Bursts and heavy tails in temporal and sequential dynamics of foraging decisions.

PubMed

Jung, Kanghoon; Jang, Hyeran; Kralik, Jerald D; Jeong, Jaeseung

2014-08-01

A fundamental understanding of behavior requires predicting when and what an individual will choose. However, the actual temporal and sequential dynamics of successive choices made among multiple alternatives remain unclear. In the current study, we tested the hypothesis that there is a general bursting property in both the timing and sequential patterns of foraging decisions. We conducted a foraging experiment in which rats chose among four different foods over a continuous two-week time period. Regarding when choices were made, we found bursts of rapidly occurring actions, separated by time-varying inactive periods, partially based on a circadian rhythm. Regarding what was chosen, we found sequential dynamics in affective choices characterized by two key features: (a) a highly biased choice distribution; and (b) preferential attachment, in which the animals were more likely to choose what they had previously chosen. To capture the temporal dynamics, we propose a dual-state model consisting of active and inactive states. We also introduce a satiation-attainment process for bursty activity, and a non-homogeneous Poisson process for longer inactivity between bursts. For the sequential dynamics, we propose a dual-control model consisting of goal-directed and habit systems, based on outcome valuation and choice history, respectively. This study provides insights into how the bursty nature of behavior emerges from the interaction of different underlying systems, leading to heavy tails in the distribution of behavior over time and choices.

Evolution of the social network of scientific collaborations

NASA Astrophysics Data System (ADS)

Barabasi, Albert-Laszlo; Jeong, Hawoong; Neda, Zoltan; Ravasz, Erzsebet; Schubert, Andras; Vicsek, Tamas

2002-03-01

The co-authorship network of scientists represents a prototype of complex evolving networks. By mapping the electronic database containing all relevant journals in mathematics and neuro-science for an eight-year period (1991-98), we infer the dynamic and the structural mechanisms that govern the evolution and topology of this complex system. First, empirical measurements allow us to uncover the topological measures that characterize the network at a given moment, as well as the time evolution of these quantities. The results indicate that the network is scale-free, and that the network evolution is governed by preferential attachment, affecting both internal and external links. However, in contrast with most model predictions the average degree increases in time, and the node separation decreases. Second, we propose a simple model that captures the network's time evolution. Third, numerical simulations are used to uncover the behavior of quantities that could not be predicted analytically.

Disease invasion risk in a growing population.

PubMed

Yuan, Sanling; van den Driessche, P; Willeboordse, Frederick H; Shuai, Zhisheng; Ma, Junling

2016-09-01

The spread of an infectious disease may depend on the population size. For simplicity, classic epidemic models assume homogeneous mixing, usually standard incidence or mass action. For standard incidence, the contact rate between any pair of individuals is inversely proportional to the population size, and so the basic reproduction number (and thus the initial exponential growth rate of the disease) is independent of the population size. For mass action, this contact rate remains constant, predicting that the basic reproduction number increases linearly with the population size, meaning that disease invasion is easiest when the population is largest. In this paper, we show that neither of these may be true on a slowly evolving contact network: the basic reproduction number of a short epidemic can reach its maximum while the population is still growing. The basic reproduction number is proportional to the spectral radius of a contact matrix, which is shown numerically to be well approximated by the average excess degree of the contact network. We base our analysis on modeling the dynamics of the average excess degree of a random contact network with constant population input, proportional deaths, and preferential attachment for contacts brought in by incoming individuals (i.e., individuals with more contacts attract more incoming contacts). In addition, we show that our result also holds for uniform attachment of incoming contacts (i.e., every individual has the same chance of attracting incoming contacts), and much more general population dynamics. Our results show that a disease spreading in a growing population may evade control if disease control planning is based on the basic reproduction number at maximum population size.

Effect of milling on particle shape and surface energy heterogeneity of needle-shaped crystals.

PubMed

Ho, Raimundo; Naderi, Majid; Heng, Jerry Y Y; Williams, Daryl R; Thielmann, Frank; Bouza, Peter; Keith, Adam R; Thiele, Greg; Burnett, Daniel J

2012-10-01

Milling and micronization of particles are routinely employed in the pharmaceutical industry to obtain small particles with desired particle size characteristics. The aim of this study is to demonstrate that particle shape is an important factor affecting the fracture mechanism in milling. Needle-shaped crystals of the β polymorph of D-mannitol were prepared from recrystallization in water. A portion of the recrystallized materials was ball-milled. Unmilled and milled sieved fractions of recrystallized D-mannitol were analyzed by dynamic image analysis (DIA) and inverse gas chromatography (IGC) at finite concentration to explain the breakage/fracture behavior. In the process of ball-milling, D-mannitol preferentially fractured along their shortest axis, exposing (011) plane with increased hydrophilicity and increased bounding rectangular aspect ratio. This is in contrary to attachment energy modeling which predicts a fracture mechanism across the (010) plane with increased hydrophobicity, and small change in particle shape. Crystal size, and more importantly, crystal shape and facet-specific mechanical properties, can dictate the fracture/cleavage behavior of organic crystalline materials. Thorough understanding of the crystal slip systems, combining attachment energy prediction with particle shape and surface characterization using DIA and IGC, are important in understanding fracture behavior of organic crystalline solids in milling and micronization.

Direct observation of the myosin Va recovery stroke that contributes to unidirectional stepping along actin.

PubMed

Shiroguchi, Katsuyuki; Chin, Harvey F; Hannemann, Diane E; Muneyuki, Eiro; De La Cruz, Enrique M; Kinosita, Kazuhiko

2011-04-01

Myosins are ATP-driven linear molecular motors that work as cellular force generators, transporters, and force sensors. These functions are driven by large-scale nucleotide-dependent conformational changes, termed "strokes"; the "power stroke" is the force-generating swinging of the myosin light chain-binding "neck" domain relative to the motor domain "head" while bound to actin; the "recovery stroke" is the necessary initial motion that primes, or "cocks," myosin while detached from actin. Myosin Va is a processive dimer that steps unidirectionally along actin following a "hand over hand" mechanism in which the trailing head detaches and steps forward ∼72 nm. Despite large rotational Brownian motion of the detached head about a free joint adjoining the two necks, unidirectional stepping is achieved, in part by the power stroke of the attached head that moves the joint forward. However, the power stroke alone cannot fully account for preferential forward site binding since the orientation and angle stability of the detached head, which is determined by the properties of the recovery stroke, dictate actin binding site accessibility. Here, we directly observe the recovery stroke dynamics and fluctuations of myosin Va using a novel, transient caged ATP-controlling system that maintains constant ATP levels through stepwise UV-pulse sequences of varying intensity. We immobilized the neck of monomeric myosin Va on a surface and observed real time motions of bead(s) attached site-specifically to the head. ATP induces a transient swing of the neck to the post-recovery stroke conformation, where it remains for ∼40 s, until ATP hydrolysis products are released. Angle distributions indicate that the post-recovery stroke conformation is stabilized by ≥ 5 k(B)T of energy. The high kinetic and energetic stability of the post-recovery stroke conformation favors preferential binding of the detached head to a forward site 72 nm away. Thus, the recovery stroke contributes to unidirectional stepping of myosin Va.

Generating clustered scale-free networks using Poisson based localization of edges

NASA Astrophysics Data System (ADS)

Türker, İlker

2018-05-01

We introduce a variety of network models using a Poisson-based edge localization strategy, which result in clustered scale-free topologies. We first verify the success of our localization strategy by realizing a variant of the well-known Watts-Strogatz model with an inverse approach, implying a small-world regime of rewiring from a random network through a regular one. We then apply the rewiring strategy to a pure Barabasi-Albert model and successfully achieve a small-world regime, with a limited capacity of scale-free property. To imitate the high clustering property of scale-free networks with higher accuracy, we adapted the Poisson-based wiring strategy to a growing network with the ingredients of both preferential attachment and local connectivity. To achieve the collocation of these properties, we used a routine of flattening the edges array, sorting it, and applying a mixing procedure to assemble both global connections with preferential attachment and local clusters. As a result, we achieved clustered scale-free networks with a computational fashion, diverging from the recent studies by following a simple but efficient approach.

Near Critical Preferential Attachment Networks have Small Giant Components

NASA Astrophysics Data System (ADS)

Eckhoff, Maren; Mörters, Peter; Ortgiese, Marcel

2018-05-01

Preferential attachment networks with power law exponent τ >3 are known to exhibit a phase transition. There is a value ρ c>0 such that, for small edge densities ρ ≤ ρ c every component of the graph comprises an asymptotically vanishing proportion of vertices, while for large edge densities ρ >ρ c there is a unique giant component comprising an asymptotically positive proportion of vertices. In this paper we study the decay in the size of the giant component as the critical edge density is approached from above. We show that the size decays very rapidly, like \\exp (-c/ √{ρ -ρ c}) for an explicit constant c>0 depending on the model implementation. This result is in contrast to the behaviour of the class of rank-one models of scale-free networks, including the configuration model, where the decay is polynomial. Our proofs rely on the local neighbourhood approximations of Dereich and Mörters (Ann Probab 41(1):329-384, 2013) and recent progress in the theory of branching random walks (Gantert et al. in Ann Inst Henri Poincaré Probab Stat 47(1):111-129, 2011).

Complex growing networks with intrinsic vertex fitness

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

Bedogne, C.; Rodgers, G. J.

2006-10-15

One of the major questions in complex network research is to identify the range of mechanisms by which a complex network can self organize into a scale-free state. In this paper we investigate the interplay between a fitness linking mechanism and both random and preferential attachment. In our models, each vertex is assigned a fitness x, drawn from a probability distribution {rho}(x). In Model A, at each time step a vertex is added and joined to an existing vertex, selected at random, with probability p and an edge is introduced between vertices with fitnesses x and y, with a ratemore » f(x,y), with probability 1-p. Model B differs from Model A in that, with probability p, edges are added with preferential attachment rather than randomly. The analysis of Model A shows that, for every fixed fitness x, the network's degree distribution decays exponentially. In Model B we recover instead a power-law degree distribution whose exponent depends only on p, and we show how this result can be generalized. The properties of a number of particular networks are examined.« less

Effects of tether attachments on the Shuttle/Tethered Satellite System dynamics

NASA Technical Reports Server (NTRS)

Gresham, L. L.; Rupp, C. C.

1979-01-01

The dynamics of the Shuttle Tethered Satellite System are influenced by attaching the tether at some point other than the center-of-masses of the Shuttle and the subsatellite. At the Shuttle, the tether attachment is made at the end of a boom deployed out of the payload bay. This attachment noticeably affects retrieval dynamics of the satellite pendulous motion. At the satellite, the tether attachment is assumed to be made on the circumference of the satellite. This attachment greatly affects the attitude motion of the satellite about its own center-of-mass. Computer simulation results are presented showing the effects of the Shuttle boom in a three-dimensional model and the effects of satellite attachment in a planar model.

Bursts and Heavy Tails in Temporal and Sequential Dynamics of Foraging Decisions

PubMed Central

Jung, Kanghoon; Jang, Hyeran; Kralik, Jerald D.; Jeong, Jaeseung

2014-01-01

A fundamental understanding of behavior requires predicting when and what an individual will choose. However, the actual temporal and sequential dynamics of successive choices made among multiple alternatives remain unclear. In the current study, we tested the hypothesis that there is a general bursting property in both the timing and sequential patterns of foraging decisions. We conducted a foraging experiment in which rats chose among four different foods over a continuous two-week time period. Regarding when choices were made, we found bursts of rapidly occurring actions, separated by time-varying inactive periods, partially based on a circadian rhythm. Regarding what was chosen, we found sequential dynamics in affective choices characterized by two key features: (a) a highly biased choice distribution; and (b) preferential attachment, in which the animals were more likely to choose what they had previously chosen. To capture the temporal dynamics, we propose a dual-state model consisting of active and inactive states. We also introduce a satiation-attainment process for bursty activity, and a non-homogeneous Poisson process for longer inactivity between bursts. For the sequential dynamics, we propose a dual-control model consisting of goal-directed and habit systems, based on outcome valuation and choice history, respectively. This study provides insights into how the bursty nature of behavior emerges from the interaction of different underlying systems, leading to heavy tails in the distribution of behavior over time and choices. PMID:25122498

Post-learning hippocampal dynamics promote preferential retention of rewarding events

PubMed Central

Gruber, Matthias J.; Ritchey, Maureen; Wang, Shao-Fang; Doss, Manoj K.; Ranganath, Charan

2016-01-01

Reward motivation is known to modulate memory encoding, and this effect depends on interactions between the substantia nigra/ ventral tegmental area complex (SN/VTA) and the hippocampus. It is unknown, however, whether these interactions influence offline neural activity in the human brain that is thought to promote memory consolidation. Here, we used functional magnetic resonance imaging (fMRI) to test the effect of reward motivation on post-learning neural dynamics and subsequent memory for objects that were learned in high- or low-reward motivation contexts. We found that post-learning increases in resting-state functional connectivity between the SN/VTA and hippocampus predicted preferential retention of objects that were learned in high-reward contexts. In addition, multivariate pattern classification revealed that hippocampal representations of high-reward contexts were preferentially reactivated during post-learning rest, and the number of hippocampal reactivations was predictive of preferential retention of items learned in high-reward contexts. These findings indicate that reward motivation alters offline post-learning dynamics between the SN/VTA and hippocampus, providing novel evidence for a potential mechanism by which reward could influence memory consolidation. PMID:26875624

Predicting Node Degree Centrality with the Node Prominence Profile

PubMed Central

Yang, Yang; Dong, Yuxiao; Chawla, Nitesh V.

2014-01-01

Centrality of a node measures its relative importance within a network. There are a number of applications of centrality, including inferring the influence or success of an individual in a social network, and the resulting social network dynamics. While we can compute the centrality of any node in a given network snapshot, a number of applications are also interested in knowing the potential importance of an individual in the future. However, current centrality is not necessarily an effective predictor of future centrality. While there are different measures of centrality, we focus on degree centrality in this paper. We develop a method that reconciles preferential attachment and triadic closure to capture a node's prominence profile. We show that the proposed node prominence profile method is an effective predictor of degree centrality. Notably, our analysis reveals that individuals in the early stage of evolution display a distinctive and robust signature in degree centrality trend, adequately predicted by their prominence profile. We evaluate our work across four real-world social networks. Our findings have important implications for the applications that require prediction of a node's future degree centrality, as well as the study of social network dynamics. PMID:25429797

Is Vocabulary Growth Influenced by the Relations among Words in a Language Learner's Vocabulary?

ERIC Educational Resources Information Center

Sailor, Kevin M.

2013-01-01

Several recent studies have explored the applicability of the preferential attachment principle to account for vocabulary growth. According to this principle, network growth can be described by a process in which existing nodes recruit new nodes with a probability that is an increasing function of their connectivity within the existing network.…

Learning Words over Time: The Role of Stimulus Repetition in Mutual Exclusivity

ERIC Educational Resources Information Center

Mather, Emily; Plunkett, Kim

2009-01-01

During the second year of life, infants develop a preference to attach novel labels to novel objects. This behavior is commonly known as "mutual exclusivity" (Markman, 1989). In an intermodal preferential looking experiment with 19.5- and 22.5-month-olds, stimulus repetition was critical for observing mutual exclusivity. On the first…

The basolateral vesicle sorting machinery and basolateral proteins are recruited to the site of enteropathogenic E. coli microcolony growth at the apical membrane.

PubMed

Pedersen, Gitte A; Jensen, Helene H; Schelde, Anne-Sofie B; Toft, Charlotte; Pedersen, Hans N; Ulrichsen, Maj; Login, Frédéric H; Amieva, Manuel R; Nejsum, Lene N

2017-01-01

Foodborne Enteropathogenic Escherichia coli (EPEC) infections of the small intestine cause diarrhea especially in children and are a major cause of childhood death in developing countries. EPEC infects the apical membrane of the epithelium of the small intestine by attaching, effacing the microvilli under the bacteria and then forming microcolonies on the cell surface. We first asked the question where on epithelial cells EPEC attaches and grows. Using models of polarized epithelial monolayers, we evaluated the sites of initial EPEC attachment to the apical membrane and found that EPEC preferentially attached over the cell-cell junctions and formed microcolonies preferentially where three cells come together at tricellular tight junctions. The ability of EPEC to adhere increased when host cell polarity was compromised yielding EPEC access to basolateral proteins. EPEC pedestals contain basolateral cytoskeletal proteins. Thus, we asked if attached EPEC causes reorganization the protein composition of the host cell plasma membrane at sites of microcolony formation. We found that EPEC microcolony growth at the apical membrane resulted in a local accumulation of basolateral plasma membrane proteins surrounding the microcolony. Basolateral marker protein aquaporin-3 localized to forming EPEC microcolonies. Components of the basolateral vesicle targeting machinery were re-routed. The Exocyst (Exo70) was recruited to individual EPEC as was the basolateral vesicle SNARE VAMP-3. Moreover, several Rab variants were also recruited to the infection site, and their dominant-negative equivalents were not. To quantitatively study the recruitment of basolateral proteins, we created a pulse of the temperature sensitive basolateral VSVG, VSVG3-SP-GFP, from the trans-Golgi Network. We found that after release from the TGN, significantly more VSVG3-SP-GFP accumulated at the site of microcolony growth than on equivalent membrane regions of uninfected cells. This suggests that trafficking of vesicles destined for the basolateral membrane are redirected to the apical site of microcolony growth. Thus, in addition to disrupting host cell fence function, local host cell plasma membrane protein composition is changed by altered protein trafficking and recruitment of basolateral proteins to the apical microcolony. This may aid EPEC attachment and subsequent microcolony growth.

The basolateral vesicle sorting machinery and basolateral proteins are recruited to the site of enteropathogenic E. coli microcolony growth at the apical membrane

PubMed Central

Pedersen, Gitte A.; Jensen, Helene H.; Schelde, Anne-Sofie B.; Toft, Charlotte; Pedersen, Hans N.; Ulrichsen, Maj; Login, Frédéric H.; Amieva, Manuel R.

2017-01-01

Foodborne Enteropathogenic Escherichia coli (EPEC) infections of the small intestine cause diarrhea especially in children and are a major cause of childhood death in developing countries. EPEC infects the apical membrane of the epithelium of the small intestine by attaching, effacing the microvilli under the bacteria and then forming microcolonies on the cell surface. We first asked the question where on epithelial cells EPEC attaches and grows. Using models of polarized epithelial monolayers, we evaluated the sites of initial EPEC attachment to the apical membrane and found that EPEC preferentially attached over the cell-cell junctions and formed microcolonies preferentially where three cells come together at tricellular tight junctions. The ability of EPEC to adhere increased when host cell polarity was compromised yielding EPEC access to basolateral proteins. EPEC pedestals contain basolateral cytoskeletal proteins. Thus, we asked if attached EPEC causes reorganization the protein composition of the host cell plasma membrane at sites of microcolony formation. We found that EPEC microcolony growth at the apical membrane resulted in a local accumulation of basolateral plasma membrane proteins surrounding the microcolony. Basolateral marker protein aquaporin-3 localized to forming EPEC microcolonies. Components of the basolateral vesicle targeting machinery were re-routed. The Exocyst (Exo70) was recruited to individual EPEC as was the basolateral vesicle SNARE VAMP-3. Moreover, several Rab variants were also recruited to the infection site, and their dominant-negative equivalents were not. To quantitatively study the recruitment of basolateral proteins, we created a pulse of the temperature sensitive basolateral VSVG, VSVG3-SP-GFP, from the trans-Golgi Network. We found that after release from the TGN, significantly more VSVG3-SP-GFP accumulated at the site of microcolony growth than on equivalent membrane regions of uninfected cells. This suggests that trafficking of vesicles destined for the basolateral membrane are redirected to the apical site of microcolony growth. Thus, in addition to disrupting host cell fence function, local host cell plasma membrane protein composition is changed by altered protein trafficking and recruitment of basolateral proteins to the apical microcolony. This may aid EPEC attachment and subsequent microcolony growth. PMID:28636623

Preferential flow in the vadose zone and interface dynamics: Impact of microbial exudates

NASA Astrophysics Data System (ADS)

Li, Biting; Pales, Ashley R.; Clifford, Heather M.; Kupis, Shyla; Hennessy, Sarah; Liang, Wei-Zhen; Moysey, Stephen; Powell, Brian; Finneran, Kevin T.; Darnault, Christophe J. G.

2018-03-01

In the hydrological cycle, the infiltration process is a critical component in the distribution of water into the soil and in the groundwater system. The nonlinear dynamics of the soil infiltration process yield preferential flow which affects the water distribution in soil. Preferential flow is influenced by the interactions between water, soil, plants, and microorganisms. Although the relationship among the plant roots, their rhizodeposits and water transport in soil has been the subject of extensive study, the effect of microbial exudates has been studied in only a few cases. Here the authors investigated the influence of two artificial microbial exudates-catechol and riboflavin-on the infiltration process, particularly unstable fingered flow, one form of preferential flow. Flow experiments investigating the effects of types and concentrations of microbial exudates on unstable fingered flow were conducted in a two-dimensional tank that was filled with ASTM

Cell behavior on gallium nitride surfaces: peptide affinity attachment versus covalent functionalization.

PubMed

Foster, Corey M; Collazo, Ramon; Sitar, Zlatko; Ivanisevic, Albena

2013-07-02

Gallium nitride is a wide band gap semiconductor that demonstrates a unique set of optical and electrical properties as well as aqueous stability and biocompatibility. This combination of properties makes gallium nitride a strong candidate for use in chemical and biological applications such as sensors and neural interfaces. Molecular modification can be used to enhance the functionality and properties of the gallium nitride surface. Here, gallium nitride surfaces were functionalized with a PC12 cell adhesion promoting peptide using covalent and affinity driven attachment methods. The covalent scheme proceeded by Grignard reaction and olefin metathesis while the affinity driven scheme utilized the recognition peptide isolated through phage display. This study shows that the method of attaching the adhesion peptide influences PC12 cell adhesion and differentiation as measured by cell density and morphological analysis. Covalent attachment promoted monolayer and dispersed cell adhesion while affinity driven attachment promoted multilayer cell agglomeration. Higher cell density was observed on surfaces modified using the recognition peptide. The results suggest that the covalent and affinity driven attachment methods are both suitable for promoting PC12 cell adhesion to the gallium nitride surface, though each method may be preferentially suited for distinct applications.

Topology and evolution of technology innovation networks

NASA Astrophysics Data System (ADS)

Valverde, Sergi; Solé, Ricard V.; Bedau, Mark A.; Packard, Norman

2007-11-01

The web of relations linking technological innovation can be fairly described in terms of patent citations. The resulting patent citation network provides a picture of the large-scale organization of innovations and its time evolution. Here we study the patterns of change of patents registered by the U.S. Patent and Trademark Office. We show that the scaling behavior exhibited by this network is consistent with a preferential attachment mechanism together with a Weibull-shaped aging term. Such an attachment kernel is shared by scientific citation networks, thus indicating a universal type of mechanism linking ideas and designs and their evolution. The implications for evolutionary theory of innovation are discussed.

Constraints and entropy in a model of network evolution

NASA Astrophysics Data System (ADS)

Tee, Philip; Wakeman, Ian; Parisis, George; Dawes, Jonathan; Kiss, István Z.

2017-11-01

Barabási-Albert's "Scale Free" model is the starting point for much of the accepted theory of the evolution of real world communication networks. Careful comparison of the theory with a wide range of real world networks, however, indicates that the model is in some cases, only a rough approximation to the dynamical evolution of real networks. In particular, the exponent γ of the power law distribution of degree is predicted by the model to be exactly 3, whereas in a number of real world networks it has values between 1.2 and 2.9. In addition, the degree distributions of real networks exhibit cut offs at high node degree, which indicates the existence of maximal node degrees for these networks. In this paper we propose a simple extension to the "Scale Free" model, which offers better agreement with the experimental data. This improvement is satisfying, but the model still does not explain why the attachment probabilities should favor high degree nodes, or indeed how constraints arrive in non-physical networks. Using recent advances in the analysis of the entropy of graphs at the node level we propose a first principles derivation for the "Scale Free" and "constraints" model from thermodynamic principles, and demonstrate that both preferential attachment and constraints could arise as a natural consequence of the second law of thermodynamics.

Coevolving complex networks in the model of social interactions

NASA Astrophysics Data System (ADS)

Raducha, Tomasz; Gubiec, Tomasz

2017-04-01

We analyze Axelrod's model of social interactions on coevolving complex networks. We introduce four extensions with different mechanisms of edge rewiring. The models are intended to catch two kinds of interactions-preferential attachment, which can be observed in scientists or actors collaborations, and local rewiring, which can be observed in friendship formation in everyday relations. Numerical simulations show that proposed dynamics can lead to the power-law distribution of nodes' degree and high value of the clustering coefficient, while still retaining the small-world effect in three models. All models are characterized by two phase transitions of a different nature. In case of local rewiring we obtain order-disorder discontinuous phase transition even in the thermodynamic limit, while in case of long-distance switching discontinuity disappears in the thermodynamic limit, leaving one continuous phase transition. In addition, we discover a new and universal characteristic of the second transition point-an abrupt increase of the clustering coefficient, due to formation of many small complete subgraphs inside the network.

Inside the Mechanics of Network Development: How Competition and Strategy Reorganize European Air Traffic

NASA Technical Reports Server (NTRS)

Huber, Hans

2006-01-01

Air transport forms complex networks that can be measured in order to understand its structural characteristics and functional properties. Recent models for network growth (i.e., preferential attachment, etc.) remain stochastic and do not seek to understand other network-specific mechanisms that may account for their development in a more microscopic way. Air traffic is made up of many constituent airlines that are either privately or publicly owned and that operate their own networks. They follow more or less similar business policies each. The way these airline networks organize among themselves into distinct traffic distributions reveals complex interaction among them, which in turn can be aggregated into larger (macro-) traffic distributions. Our approach allows for a more deterministic methodology that will assess the impact of airline strategies on the distinct distributions for air traffic, particularly inside Europe. One key question this paper is seeking to answer is whether there are distinct patterns of preferential attachment for given classes of airline networks to distinct types of European airports. Conclusions about the advancing degree of concentration in this industry and the airline operators that accelerate this process can be drawn.

The Matthew effect in empirical data

PubMed Central

Perc, Matjaž

2014-01-01

The Matthew effect describes the phenomenon that in societies, the rich tend to get richer and the potent even more powerful. It is closely related to the concept of preferential attachment in network science, where the more connected nodes are destined to acquire many more links in the future than the auxiliary nodes. Cumulative advantage and success-breads-success also both describe the fact that advantage tends to beget further advantage. The concept is behind the many power laws and scaling behaviour in empirical data, and it is at the heart of self-organization across social and natural sciences. Here, we review the methodology for measuring preferential attachment in empirical data, as well as the observations of the Matthew effect in patterns of scientific collaboration, socio-technical and biological networks, the propagation of citations, the emergence of scientific progress and impact, career longevity, the evolution of common English words and phrases, as well as in education and brain development. We also discuss whether the Matthew effect is due to chance or optimization, for example related to homophily in social systems or efficacy in technological systems, and we outline possible directions for future research. PMID:24990288

Dynamic preferential allocation to arbuscular mycorrhizal fungi explains fungal succession and coexistence.

PubMed

Bachelot, Benedicte; Lee, Charlotte T

2018-02-01

Evidence accumulates about the role of arbuscular mycorrhizal (AM) fungi in shaping plant communities, but little is known about the factors determining the biomass and coexistence of several types of AM fungi in a plant community. Here, using a consumer-resource framework that treats the relationship between plants and fungi as simultaneous, reciprocal exploitation, we investigated what patterns of dynamic preferential plant carbon allocation to empirically-defined fungal types (on-going partner choice) would be optimal for plants, and how these patterns depend on successional dynamics. We found that ruderal AM fungi can dominate under low steady-state nutrient availability, and competitor AM fungi can dominate at higher steady-state nutrient availability; these are conditions characteristic of early and late succession, respectively. We also found that dynamic preferential allocation alone can maintain a diversity of mutualists, suggesting that on-going partner choice is a new coexistence mechanism for mutualists. Our model can therefore explain both mutualist coexistence and successional strategy, providing a powerful tool to derive testable predictions. © 2017 by the Ecological Society of America.

Love as a Battlefield: Attachment and Relationship Dynamics in Couples Identified for Male Partner Violence

ERIC Educational Resources Information Center

Allison, Colleen J.; Bartholomew, Kim; Mayseless, Ofra; Dutton, Donald G.

2008-01-01

The authors explored the attachment dynamics of heterosexual couples identified for male partner violence. Based on semistructured interviews, participants were assessed for attachment orientations. Based on a thematic analysis of the interviews, two strategies for regulating distance within these relationships were identified: pursuit and…

Preferential transport of isoproturon at a plot scale and a field scale tile-drained site

NASA Astrophysics Data System (ADS)

Zehe, Erwin; Flühler, Hannes

2001-06-01

Irrigation experiments using the tracers Brilliant Blue (BB) and Bromide (Br) were conducted on three plots of 1.4×1.4 m 2 (plot scale) and a field scale subsurface drained test site (900 m 2) to clarify mechanisms causing rapid transport of surface applied Isoproturon (IPU) during preferential flow events. One of the small plots (site 10) and the field scale test site are located on the same field. One day after irrigation of the plot scale sites the Br and IPU concentration in two vertical soil profiles as well as the macroporousity on separate profiles and hydraulic properties of single macropores were determined. During irrigation of the field scale test site discharge, soil moisture as well as the concentration of IPU and Br in the drainage outlet were measured. Preferential flow in deep penetrating earthworm burrows caused a fast breakthrough of IPU and Br into the tile drain (1.2 m depth) at the field scale site as well as leaching of IPU into the subsoil (>0.8 m) at site 10. The results suggest a hierarchy of preconditions for the occurrence of preferential flow events of which a sufficient number of deep penetrating macropores interconnected to the soil surface seems to be the most important one. Moreover there is evidence that facilitated transport of IPU attached to mobile soil particles occurred during the preferential flow events at the field scale site and site 10. The susceptibility for preferential flow as well as the susceptibility for facilitated transport appear to be intrinsic properties of the investigated soil.

Effects of atmospheric air plasma treatment of graphite and carbon felt electrodes on the anodic current from Shewanella attached cells.

PubMed

Epifanio, Monica; Inguva, Saikumar; Kitching, Michael; Mosnier, Jean-Paul; Marsili, Enrico

2015-12-01

The attachment of electrochemically active microorganisms (EAM) on an electrode is determined by both the chemistry and topography of the electrode surface. Pre-treatment of the electrode surface by atmospheric air plasma introduces hydrophilic functional groups, thereby increasing cell attachment and electroactivity in short-term experiments. In this study, we use graphite and carbon felt electrodes to grow the model EAM Shewanella loihica PV-4 at oxidative potential (0.2 V vs. Ag/AgCl). Cell attachment and electroactivity are measured through electrodynamic methods. Atmospheric air plasma pre-treatment increases cell attachment and current output at graphite electrodes by 25%, while it improves the electroactivity of the carbon felt electrodes by 450%. Air plasma pre-treatment decreased the coulombic efficiency on both carbon felt and graphite electrodes by 60% and 80%, respectively. Microbially produced flavins adsorb preferentially at the graphite electrode, and air plasma pre-treatment results in lower flavin adsorption at both graphite and carbon felt electrodes. Results show that air plasma pre-treatment is a feasible option to increase current output in bioelectrochemical systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Mechanisms of the Formation of Adenine, Guanine, and Their Analogues in UV-Irradiated Mixed NH3:H2O Molecular Ices Containing Purine

NASA Astrophysics Data System (ADS)

Bera, Partha P.; Stein, Tamar; Head-Gordon, Martin; Lee, Timothy J.

2017-08-01

We investigated the formation mechanisms of the nucleobases adenine and guanine and the nucleobase analogues hypoxanthine, xanthine, isoguanine, and 2,6-diaminopurine in a UV-irradiated mixed 10:1 H2O:NH3 ice seeded with precursor purine by using ab initio and density functional theory computations. Our quantum chemical investigations suggest that a multistep reaction mechanism involving purine cation, hydroxyl and amino radicals, together with water and ammonia, explains the experimentally obtained products in an independent study. The relative abundances of these products appear to largely follow from relative thermodynamic stabilities. The key role of the purine cation is likely to be the reason why purine is not functionalized in pure ammonia ice, where cations are promptly neutralized by free electrons from NH3 ionization. Amine group addition to purine is slightly favored over hydroxyl group attachment based on energetics, but hydroxyl is much more abundant due to higher abundance of H2O. The amino group is preferentially attached to the 6 position, giving 6-aminopurine, that is, adenine, while the hydroxyl group is preferentially attached to the 2 position, leading to 2-hydroxypurine. A second substitution by hydroxyl or amino group occurs at either the 6 or the 2 position depending on the first substitution. Given that H2O is far more abundant than NH3 in the experimentally studied ices (as well as based on interstellar abundances), xanthine and isoguanine are expected to be the most abundant bi-substituted photoproducts.

Dynamic Adhesion of Umbilical Cord Blood Endothelial Progenitor Cells under Laminar Shear Stress

PubMed Central

Angelos, Mathew G.; Brown, Melissa A.; Satterwhite, Lisa L.; Levering, Vrad W.; Shaked, Natan T.; Truskey, George A.

2010-01-01

Late outgrowth endothelial progenitor cells (EPCs) represent a promising cell source for rapid reendothelialization of damaged vasculature after expansion ex vivo and injection into the bloodstream. We characterized the dynamic adhesion of umbilical-cord-blood-derived EPCs (CB-EPCs) to surfaces coated with fibronectin. CB-EPC solution density affected the number of adherent cells and larger cells preferentially adhered at lower cell densities. The number of adherent cells varied with shear stress, with the maximum number of adherent cells and the shear stress at maximum adhesion depending upon fluid viscosity. CB-EPCs underwent limited rolling, transiently tethering for short distances before firm arrest. Immediately before arrest, the instantaneous velocity decreased independent of shear stress. A dimensional analysis indicated that adhesion was a function of the net force on the cells, the ratio of cell diffusion to sliding speed, and molecular diffusivity. Adhesion was not limited by the settling rate and was highly specific to α5β1 integrin. Total internal reflection fluorescence microscopy showed that CB-EPCs produced multiple contacts of α5β1 with the surface and the contact area grew during the first 20 min of attachment. These results demonstrate that CB-EPC adhesion from blood can occur under physiological levels of shear stress. PMID:21112278

Initial association of fresh microbial products to soil particles: a joint density fractionation and NanoSIMS study

NASA Astrophysics Data System (ADS)

Hatton, Pierre-Joseph; Remusat, Laurent; Brewer, Elizabeth; Derrien, Delphine

2014-05-01

While soil microorganisms are increasingly seen as shaping stable soil organic matter (OM) formation, the mechanisms controlling the attachment of microbial metabolites to soil particles are not fully understood yet. We investigate the spatial distribution of freshly produced microbial products among density-isolated fractions of soil using stable C and N isotopes and Nano-scale secondary ion mass spectrometry (NanoSIMS). A surface forest soil was amended with uniformly 13C/15N labeled glycine and incubated for 8 hours in gamma-irradiated and non-sterile soils. Sequential density fractionation was then performed to isolate various classes of aggregates and of single mineral particles. Eight hours after the labeled glycine addition, 7 % of the 13C and 15N was tightly bound to soil assemblages. Comparison of sterile and non-sterile treatments revealed that microbial activity was almost completely responsible for this rapid association (>85 %). The distributions of glycine-derived 13C and 15N, considered as markers of new microbial products, were mapped on particles of the non-sterile treatment using NanoSIMS. New microbial products were heterogeneously distributed and spatially decoupled at the surface of on soil particles. 13C microbial products were scarce and presumably within or in the vicinity of microbial cells. In contrast, 15N microbial products seemed evenly spread at the surface of soil particles, likely as soluble exoenzymes diffusing away from their parent cell. Macroscopic measurements among density fractions suggested that the diffusion of such 15N microbial products was spatially limited yet, because of pore space architecture. NanoSIMS images further allowed gaining insight into the attachment of the new microbial products on particle surfaces already covered by OM, in a multilayer fashion. Using an internal calibration method to determine C/N ratios of NanoSIMS images, we showed the preferential attachment of soluble microbial N-metabolites to N-rich mineral-attached OM (C/N ratios mostly < 16). Exceptions were found in dense particles, supposed to contained aluminium and iron (hydr)oxides, with the microbial N-metabolites apparently preferentially attached to C-rich mineral-attached OM (C/N ratios > 80). This work provided visual evidences that the attachment of new microbial products to the soil matrix is mediated by distinct processes for N-rich and C-rich metabolites. It also demonstrated that the pore space architecture has impact on the formation of stable OM by limiting the diffusion of soluble microbial metabolites and their access to reactive and stabilising surfaces.

How people make friends in social networking sites—A microscopic perspective

NASA Astrophysics Data System (ADS)

Hu, Haibo; Wang, Xiaofan

2012-02-01

We study the detailed growth of a social networking site with full temporal information by examining the creation process of each friendship relation that can collectively lead to the macroscopic properties of the network. We first study the reciprocal behavior of users, and find that link requests are quickly responded to and that the distribution of reciprocation intervals decays in an exponential form. The degrees of inviters/accepters are slightly negatively correlative with reciprocation time. In addition, the temporal feature of the online community shows that the distributions of intervals of user behaviors, such as sending or accepting link requests, follow a power law with a universal exponent, and peaks emerge for intervals of an integral day. We finally study the preferential selection and linking phenomena of the social networking site and find that, for the former, a linear preference holds for preferential sending and reception, and for the latter, a linear preference also holds for preferential acceptance, creation, and attachment. Based on the linearly preferential linking, we put forward an analyzable network model which can reproduce the degree distribution of the network. The research framework presented in the paper could provide a potential insight into how the micro-motives of users lead to the global structure of online social networks.

A fractal growth model: Exploring the connection pattern of hubs in complex networks

NASA Astrophysics Data System (ADS)

Li, Dongyan; Wang, Xingyuan; Huang, Penghe

2017-04-01

Fractal is ubiquitous in many real-world networks. Previous researches showed that the strong disassortativity between the hub-nodes on all length scales was the key principle that gave rise to the fractal architecture of networks. Although fractal property emerged in some models, there were few researches about the fractal growth model and quantitative analyses about the strength of the disassortativity for fractal model. In this paper, we proposed a novel inverse renormalization method, named Box-based Preferential Attachment (BPA), to build the fractal growth models in which the Preferential Attachment was performed at box level. The proposed models provided a new framework that demonstrated small-world-fractal transition. Also, we firstly demonstrated the statistical characteristic of connection patterns of the hubs in fractal networks. The experimental results showed that, given proper growing scale and added edges, the proposed models could clearly show pure small-world or pure fractal or both of them. It also showed that the hub connection ratio showed normal distribution in many real-world networks. At last, the comparisons of connection pattern between the proposed models and the biological and technical networks were performed. The results gave useful reference for exploring the growth principle and for modeling the connection patterns for real-world networks.

A coevolving model based on preferential triadic closure for social media networks

PubMed Central

Li, Menghui; Zou, Hailin; Guan, Shuguang; Gong, Xiaofeng; Li, Kun; Di, Zengru; Lai, Choy-Heng

2013-01-01

The dynamical origin of complex networks, i.e., the underlying principles governing network evolution, is a crucial issue in network study. In this paper, by carrying out analysis to the temporal data of Flickr and Epinions–two typical social media networks, we found that the dynamical pattern in neighborhood, especially the formation of triadic links, plays a dominant role in the evolution of networks. We thus proposed a coevolving dynamical model for such networks, in which the evolution is only driven by the local dynamics–the preferential triadic closure. Numerical experiments verified that the model can reproduce global properties which are qualitatively consistent with the empirical observations. PMID:23979061

Unraveling the Nature of Active Sites in Ethanol Electro-oxidation by Site-Specific Marking of a Pt Catalyst with Isotope-Labeled 13CO.

PubMed

Farias, Manuel J S; Cheuquepán, William; Tanaka, Auro A; Feliu, Juan M

2018-03-15

This works deals with the identification of preferential site-specific activation at a model Pt surface during a multiproduct reaction. The (110)-type steps of a Pt(332) surface were selectively marked by attaching isotope-labeled 13 CO molecules to them, and ethanol oxidation was probed by in situ Foureir transfrom infrared spectroscopy in order to precisely determine the specific sites at which CO 2 , acetic acid, and acetaldehyde were preferentially formed. The (110) steps were active for splitting the C-C bond, but unexpectedly, we provide evidence that the pathway of CO 2 formation was preferentially activated at (111) terraces, rather than at (110) steps. Acetaldehyde was formed at (111) terraces at potentials comparable to those for CO 2 formation also at (111) terraces, while the acetic acid formation pathway became active only when the (110) steps were released by the oxidation of adsorbed 13 CO, at potentials higher than for the formation of CO 2 at (111) terraces of the stepped surface.

Investigation of the role of hydrophilic chain length in amphiphilic perfluoropolyether/poly(ethylene glycol) networks: towards high-performance antifouling coatings.

PubMed

Wang, Yapei; Pitet, Louis M; Finlay, John A; Brewer, Lenora H; Cone, Gemma; Betts, Douglas E; Callow, Maureen E; Callow, James A; Wendt, Dean E; Hillmyer, Marc A; DeSimonea, Joseph M

2011-01-01

The facile preparation of amphiphilic network coatings having a hydrophobic dimethacryloxy-functionalized perfluoropolyether (PFPE-DMA; M(w) = 1500 g mol(-1)) crosslinked with hydrophilic monomethacryloxy functionalized poly(ethylene glycol) macromonomers (PEG-MA; M(w) = 300, 475, 1100 g mol(-1)), intended as non-toxic high-performance marine coatings exhibiting antifouling characteristics is demonstrated. The PFPE-DMA was found to be miscible with the PEG-MA. Photo-cured blends of these materials containing 10 wt% of PEG-MA oligomers did not swell significantly in water. PFPE-DMA crosslinked with the highest molecular weight PEG oligomer (ie PEG1100) deterred settlement (attachment) of algal cells and cypris larvae of barnacles compared to a PFPE control coating. Dynamic mechanical analysis of these networks revealed a flexible material. Preferential segregation of the PEG segments at the polymer/air interface resulted in enhanced antifouling performance. The cured amphiphilic PFPE/PEG films showed decreased advancing and receding contact angles with increasing PEG chain length. In particular, the PFPE/PEG1100 network had a much lower advancing contact angle than static contact angle, suggesting that the PEG1100 segments diffuse to the polymer/water interface quickly. The preferential interfacial aggregation of the larger PEG segments enables the coating surface to have a substantially enhanced resistance to settlement of spores of the green seaweed Ulva, cells of the diatom Navicula and cypris larvae of the barnacle Balanus amphitrite as well as low adhesion of sporelings (young plants) of Ulva, adhesion being lower than to a polydimethyl elastomer, Silastic T2.

eIF4B stimulates translation of long mRNAs with structured 5′ UTRs and low closed-loop potential but weak dependence on eIF4G

PubMed Central

Sen, Neelam Dabas; Zhou, Fujun; Harris, Michael S.; Ingolia, Nicholas T.

2016-01-01

DEAD-box RNA helicases eukaryotic translation initiation factor 4A (eIF4A) and Ded1 promote translation by resolving mRNA secondary structures that impede preinitiation complex (PIC) attachment to mRNA or scanning. Eukaryotic translation initiation factor 4B (eIF4B) is a cofactor for eIF4A but also might function independently of eIF4A. Ribosome profiling of mutants lacking eIF4B or with impaired eIF4A or Ded1 activity revealed that eliminating eIF4B reduces the relative translational efficiencies of many more genes than does inactivation of eIF4A, despite comparable reductions in bulk translation, and few genes display unusually strong requirements for both factors. However, either eliminating eIF4B or inactivating eIF4A preferentially impacts mRNAs with longer, more structured 5′ untranslated regions (UTRs). These findings reveal an eIF4A-independent role for eIF4B in addition to its function as eIF4A cofactor in promoting PIC attachment or scanning on structured mRNAs. eIF4B, eIF4A, and Ded1 mutations also preferentially impair translation of longer mRNAs in a fashion mitigated by the ability to form closed-loop messenger ribonucleoprotein particles (mRNPs) via eIF4F–poly(A)-binding protein 1 (Pab1) association, suggesting cooperation between closed-loop assembly and eIF4B/helicase functions. Remarkably, depleting eukaryotic translation initiation factor 4G (eIF4G), the scaffold subunit of eukaryotic translation initiation factor 4F (eIF4F), preferentially impacts short mRNAs with strong closed-loop potential and unstructured 5′ UTRs, exactly the opposite features associated with hyperdependence on the eIF4B/helicases. We propose that short, highly efficient mRNAs preferentially depend on the stimulatory effects of eIF4G-dependent closed-loop assembly. PMID:27601676

Design of a space shuttle structural dynamics model

NASA Technical Reports Server (NTRS)

1972-01-01

A 1/8 scale structural dynamics model of a parallel burn space shuttle has been designed. Basic objectives were to represent the significant low frequency structural dynamic characteristics while keeping the fabrication costs low. The model was derived from the proposed Grumman Design 619 space shuttle. The design includes an orbiter, two solid rocket motors (SRM) and an external tank (ET). The ET consists of a monocoque LO2 tank an interbank skirt with three frames to accept SRM attachment members, an LH2 tank with 10 frames of which 3 provide for orbiter attachment members, and an aft skirt with on frame to provide for aft SRM attachment members. The frames designed for the SRM attachments are fitted with transverse struts to take symmetric loads.

A class of vertex-edge-growth small-world network models having scale-free, self-similar and hierarchical characters

NASA Astrophysics Data System (ADS)

Ma, Fei; Su, Jing; Hao, Yongxing; Yao, Bing; Yan, Guanghui

2018-02-01

The problem of uncovering the internal operating function of network models is intriguing, demanded and attractive in researches of complex networks. Notice that, in the past two decades, a great number of artificial models are built to try to answer the above mentioned task. Based on the different growth ways, these previous models can be divided into two categories, one type, possessing the preferential attachment, follows a power-law P(k) ∼k-γ, 2 < γ < 3. The other has exponential-scaling feature, P(k) ∼α-k. However, there are no models containing above two kinds of growth ways to be presented, even the study of interconnection between these two growth manners in the same model is lacking. Hence, in this paper, we construct a class of planar and self-similar graphs motivated from a new attachment way, vertex-edge-growth network-operation, more precisely, the couple of both them. We report that this model is sparse, small world and hierarchical. And then, not only is scale-free feature in our model, but also lies the degree parameter γ(≈ 3 . 242) out the typical range. Note that, we suggest that the coexistence of multiple vertex growth ways will have a prominent effect on the power-law parameter γ, and the preferential attachment plays a dominate role on the development of networks over time. At the end of this paper, we obtain an exact analytical expression for the total number of spanning trees of models and also capture spanning trees entropy which we have compared with those of their corresponding component elements.

The effect of metal microstructure on the initial attachment of Escherichia coli to 1010 carbon steel.

PubMed

Javed, M A; Stoddart, P R; McArthur, S L; Wade, S A

2013-09-01

Metallurgical features have been shown to play an important role in the attachment of microorganisms to metal surfaces. In the present study, the influence of the microstructure of as-received (AR) and heat-treated (HT) 1010 carbon steel on the initial attachment of bacteria was investigated. Heat treatment was carried out with the aim of increasing the grain size of the carbon steel coupons. Mirror-polished carbon steel coupons were immersed in a minimal medium inoculated with Escherichia coli (ATCC 25922) to investigate the early (15, 30 and 60 min) and relatively longer-term (4 h) stages of bacterial attachment. The results showed preferential colonisation of bacteria on the grain boundaries of the steel coupons. The bacterial attachment to AR steel coupons was relatively uniform compared to the HT steel coupons where an increased number of localised aggregates of bacteria were found. Quantitative analysis showed that the ratio of the total number of isolated (i.e., single) bacteria to the number of bacteria in aggregates was significantly higher on the AR coupons than the HT coupons. Longer-term immersion studies showed production of extracellular polymeric substances by the bacteria and corrosion at the grain boundaries on both types of steel coupon tested.

Stability of Proteins in Carbohydrates and Other Additives during Freezing: The Human Growth Hormone as a Case Study.

PubMed

Arsiccio, Andrea; Pisano, Roberto

2017-09-21

Molecular dynamics is here used to elucidate the mechanism of protein stabilization by carbohydrates and other additives during freezing. More specifically, we used molecular dynamics simulations to obtain a quantitative estimation of the capability of various cryoprotectants to preserve a model protein, the human growth hormone, against freezing stresses. Three mechanisms were investigated, preferential exclusion, water replacement, and vitrification. Model simulations were finally validated upon experimental data in terms of the ability of excipients to prevent protein aggregation. Overall, we found that the preferential exclusion and vitrification mechanisms are important during the whole freezing process, while water replacement becomes dominant only toward the end of the cryoconcentration phase. The disaccharides were found to be the most efficient excipients, in regard to both preferential exclusion and water replacement. Moreover, sugars were in general more efficient than other excipients, such as glycine or sorbitol.

Thermodynamics of Micelle Formation and Membrane Fusion Modulate Antimicrobial Lipopeptide Activity

PubMed Central

Lin, Dejun; Grossfield, Alan

2015-01-01

Antimicrobial lipopeptides (AMLPs) are antimicrobial drug candidates that preferentially target microbial membranes. One class of AMLPs, composed of cationic tetrapeptides attached to an acyl chain, have minimal inhibitory concentrations in the micromolar range against a range of bacteria and fungi. Previously, we used coarse-grained molecular dynamics simulations and free energy methods to study the thermodynamics of their interaction with membranes in their monomeric state. Here, we extended the study to the biologically relevant micellar state, using, to our knowledge, a novel reaction coordinate based on hydrophobic contacts. Using umbrella sampling along this reaction coordinate, we identified the critical transition states when micelles insert into membranes. The results indicate that the binding of these AMLP micelles to membranes is thermodynamically favorable, but in contrast to the monomeric case, there are significant free energy barriers. The height of these free energy barriers depends on the membrane composition, suggesting that the AMLPs’ ability to selectively target bacterial membranes may be as much kinetic as thermodynamic. This mechanism highlights the importance of considering oligomeric state in solution as criterion when optimizing peptides or lipopeptides as antibiotic leads. PMID:26287627

Population Fluctuation Promotes Cooperation in Networks

PubMed Central

Miller, Steve; Knowles, Joshua

2015-01-01

We consider the problem of explaining the emergence and evolution of cooperation in dynamic network-structured populations. Building on seminal work by Poncela et al., which shows how cooperation (in one-shot prisoner’s dilemma) is supported in growing populations by an evolutionary preferential attachment (EPA) model, we investigate the effect of fluctuations in the population size. We find that a fluctuating model – based on repeated population growth and truncation – is more robust than Poncela et al.’s in that cooperation flourishes for a wider variety of initial conditions. In terms of both the temptation to defect, and the types of strategies present in the founder network, the fluctuating population is found to lead more securely to cooperation. Further, we find that this model will also support the emergence of cooperation from pre-existing non-cooperative random networks. This model, like Poncela et al.’s, does not require agents to have memory, recognition of other agents, or other cognitive abilities, and so may suggest a more general explanation of the emergence of cooperation in early evolutionary transitions, than mechanisms such as kin selection, direct and indirect reciprocity. PMID:26061705

The role of social and ecological processes in structuring animal populations: a case study from automated tracking of wild birds

PubMed Central

Farine, Damien R.; Firth, Josh A.; Aplin, Lucy M.; Crates, Ross A.; Culina, Antica; Garroway, Colin J.; Hinde, Camilla A.; Kidd, Lindall R.; Milligan, Nicole D.; Psorakis, Ioannis; Radersma, Reinder; Verhelst, Brecht; Voelkl, Bernhard; Sheldon, Ben C.

2015-01-01

Both social and ecological factors influence population process and structure, with resultant consequences for phenotypic selection on individuals. Understanding the scale and relative contribution of these two factors is thus a central aim in evolutionary ecology. In this study, we develop a framework using null models to identify the social and spatial patterns that contribute to phenotypic structure in a wild population of songbirds. We used automated technologies to track 1053 individuals that formed 73 737 groups from which we inferred a social network. Our framework identified that both social and spatial drivers contributed to assortment in the network. In particular, groups had a more even sex ratio than expected and exhibited a consistent age structure that suggested local association preferences, such as preferential attachment or avoidance. By contrast, recent immigrants were spatially partitioned from locally born individuals, suggesting differential dispersal strategies by phenotype. Our results highlight how different scales of social decision-making, ranging from post-natal dispersal settlement to fission–fusion dynamics, can interact to drive phenotypic structure in animal populations. PMID:26064644

Revisiting structure and dynamics of preferential solvation of K(I) ion in aqueous ammonia using QMCF-MD simulation

NASA Astrophysics Data System (ADS)

Hidayat, Yuniawan; Pranowo, Harno Dwi; Armunanto, Ria

2018-05-01

Structure and dynamics of preferential solvation of K(I) ion in aqueous ammonia have been reinvestigated using ab initio quantum mechanical charge field (QMCF) molecular dynamics (MD) simulation. The average coordination number of the first solvation consists of 2 ammonia and 4 waters. The mean residence time is less than 2 ps confirming the rapid mobility of ligands. The distance evolution data shows the frequent of ligand exchanges. The second solvation shell shows a more labile structure. The NBO analysis of the first shell structure emphasizes that interaction of K(I)-H2O is stronger than K(I)-NH3. The Wiberg bond confirms a weak electrostatic of ion-ligand interaction.

Evolving network simulation study. From regular lattice to scale free network

NASA Astrophysics Data System (ADS)

Makowiec, D.

2005-12-01

The Watts-Strogatz algorithm of transferring the square lattice to a small world network is modified by introducing preferential rewiring constrained by connectivity demand. The evolution of the network is two-step: sequential preferential rewiring of edges controlled by p and updating the information about changes done. The evolving system self-organizes into stationary states. The topological transition in the graph structure is noticed with respect to p. Leafy phase a graph formed by multiple connected vertices (graph skeleton) with plenty of leaves attached to each skeleton vertex emerges when p is small enough to pretend asynchronous evolution. Tangling phase where edges of a graph circulate frequently among low degree vertices occurs when p is large. There exist conditions at which the resulting stationary network ensemble provides networks which degree distribution exhibit power-law decay in large interval of degrees.

Reliance on leaders and social institutions: an attachment perspective.

PubMed

Mayseless, Ofra; Popper, Micha

2007-03-01

The ramifications of attachment processes in adulthood at the societal level are explored, specifically, why and under what circumstances followers form attachment relationships with a leader, and how the variability in these relationships can reflect the followers' internal working models of attachment. It is argued that in crisis situations, individuals tend to form affectional bonds with (mostly charismatic) leaders that function in many respects like an attachment relationship between a child and a parent. Relations between individuals and various social institutions, such as community or state, are likewise portrayed as involving attachment dynamics. The provision of security and protection (the safe haven and the secure base functions) by social structures, institutions, and leaders is seen as needed because of the inherent perceived imperfection and fallibility of "regular" attachment figures in adulthood (e.g., parents, friends, and romantic partners). This reliance on leaders and social institutions is seen as reflecting the normative diversification in attachment dynamics that takes place with development. Cultural and individual variations in these processes are also considered.

On the use of attachment modes in substructure coupling for dynamic analysis

NASA Technical Reports Server (NTRS)

Craig, R. R., Jr.; Chang, C.-J.

1977-01-01

Substructure coupling or component-mode synthesis may be employed in the solution of dynamics problems for complex structures. Although numerous substructure-coupling methods have been devised, little attention has been devoted to methods employing attachment modes. In the present paper the various mode sets (normal modes, constraint modes, attachment modes) are defined. A generalized substructure-coupling procedure is described. Those substructure-coupling methods which employ attachment modes are described in detail. One of these methods is shown to lead to results (e.g., system natural frequencies) comparable to or better than those obtained by the Hurty (1965) method.

Momentum-imaging apparatus for the study of dissociative electron attachment dynamics

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

Moradmand, A.; Williams, J. B.; Landers, A. L.

An ion-momentum spectrometer is used to study the dissociative dynamics of electron attachment to molecules. A skimmed, supersonic gas jet is crossed with a pulsed beam of low-energy electrons, and the resulting negative ions are extracted toward a time- and position-sensitive detector. Calculations of the momentum in three dimensions may be used to determine the angular dependence of dissociative attachment as well as the energetics of the reaction.

Identifying protein complex by integrating characteristic of core-attachment into dynamic PPI network.

PubMed

Shen, Xianjun; Yi, Li; Jiang, Xingpeng; He, Tingting; Yang, Jincai; Xie, Wei; Hu, Po; Hu, Xiaohua

2017-01-01

How to identify protein complex is an important and challenging task in proteomics. It would make great contribution to our knowledge of molecular mechanism in cell life activities. However, the inherent organization and dynamic characteristic of cell system have rarely been incorporated into the existing algorithms for detecting protein complexes because of the limitation of protein-protein interaction (PPI) data produced by high throughput techniques. The availability of time course gene expression profile enables us to uncover the dynamics of molecular networks and improve the detection of protein complexes. In order to achieve this goal, this paper proposes a novel algorithm DCA (Dynamic Core-Attachment). It detects protein-complex core comprising of continually expressed and highly connected proteins in dynamic PPI network, and then the protein complex is formed by including the attachments with high adhesion into the core. The integration of core-attachment feature into the dynamic PPI network is responsible for the superiority of our algorithm. DCA has been applied on two different yeast dynamic PPI networks and the experimental results show that it performs significantly better than the state-of-the-art techniques in terms of prediction accuracy, hF-measure and statistical significance in biology. In addition, the identified complexes with strong biological significance provide potential candidate complexes for biologists to validate.

Stalking as paranoid attachment: a typological and dynamic model.

PubMed

Wilson, John S; Ermshar, Annette L; Welsh, Robert K

2006-06-01

Stalking encompasses a wide range of behavioral patterns, risk factors, interpersonal dynamics, and dangerousness. To account for these diverse phenomena, we propose that stalking behavior is best conceptualized by a dynamic interaction of attachment styles and psychodynamic phenomena. This paper articulates a model that explains stalking behavior within the framework of attachment theory. Four prototypical configurations of stalkers and their victims are developed. Each configuration is discussed in terms of a pattern of internal representations, affective constellations, combinations of aggression and narcissism, and potential for future violence. The four configurations proposed here are maintained through stalkers' over ideational linkage fantasies and projective identifications, which range from shame-prone and needy idealization to malevolent torment of the victim. Our model arrays erotomanic, jealous, and persecutory attachments along a continuum of increasingly paranoid and pathological identifications. We argue that these prototypical attachment configurations provide a theoretically driven means of differentiating phases of stalking, and as such provide useful leads in the empirical study and clinical assessment, treatment, and management of stalkers.

Preferential solvation of lysozyme in dimethyl sulfoxide/water binary mixture probed by terahertz spectroscopy.

PubMed

Das, Dipak Kumar; Patra, Animesh; Mitra, Rajib Kumar

2016-09-01

We report the changes in the hydration dynamics around a model protein hen egg white lysozyme (HEWL) in water-dimethyl sulfoxide (DMSO) binary mixture using THz time domain spectroscopy (TTDS) technique. DMSO molecules get preferentially solvated at the protein surface, as indicated by circular dichroism (CD) and Fourier transform infrared (FTIR) study in the mid-infrared region, resulting in a conformational change in the protein, which consequently modifies the associated hydration dynamics. As a control we also study the collective hydration dynamics of water-DMSO binary mixture and it is found that it follows a non-ideal behavior owing to the formation of DMSO-water clusters. It is observed that the cooperative dynamics of water at the protein surface does follow the DMSO-mediated conformational modulation of the protein. Copyright © 2016 Elsevier B.V. All rights reserved.

Surface structural conformations of fibrinogen polypeptides for improved biocompatibility.

PubMed

Yaseen, Mohammed; Zhao, Xiubo; Freund, Amy; Seifalian, Alexander M; Lu, Jian R

2010-05-01

This work reports on how incorporation of silica nanocages into poly(urethane) copolymers (PU) affects conformational orientations of adsorbed fibrinogen and how different surfaces subsequently influenced HeLa cell attachment and proliferation. Incorporation of 2 wt% silica nanocages into poly(urethane) (PU4) substantially altered the surface topography of the films and some 50% of the surface was covered with the nanocages due to their preferential exposure. AFM studies revealed the deposition of a dense protein network on the soft polymeric domains of PU4 and much reduced fibrinogen adsorption on the hard nanocage domains. As on the bare SiO(2) control surface, fibrinogen molecules adsorbed on top of the hard nanocages mainly took the dominant trinodular structures in monomeric and dimeric forms. In addition, net positively charged long alpha chains were prone to being hidden beneath the D domains whilst gamma chains predominantly remained exposed. Dynamic interfacial adsorption as probed by spectroscopic ellipsometry revealed fast changes in interfacial conformation induced by electrostatic interactions between different segments of fibrinogen and the surface, consistent with the AFM imaging. On the PU surfaces without nanocage incorporation (PUA), however, adsorbed fibrinogen molecules formed beads-like chain networks, consistent with the structure featured on the soft PU4 domains, showing very different effects of surface chemical nature. Monoclonal antibodies specific to the alpha and gamma chains showed reduced alpha but increased gamma chain binding at the silicon oxide control and PU4 surfaces, whilst on the PUA, C18 and amine surfaces (organic surface controls) the opposite binding trend was detected with alpha chain binding dominant, showing different fibrinogen conformations. Cell attachment studies revealed differences in cell attachment and proliferation, consistent with the different polypeptide conformations on the two types of surfaces, showing a strong preference to the extent of exposure of gamma chains. Crown Copyright 2010. Published by Elsevier Ltd. All rights reserved.

Sampling silica and ferrihydrite colloids with fiberglass wicks under unsaturated conditions.

PubMed

Shira, Jason M; Williams, Barbara C; Flury, Markus; Czigány, Szabolcs; Tuller, Markus

2006-01-01

The suitability of passive capillary samplers (PCAPS) for collection of representative colloid samples under partially saturated conditions was evaluated by investigating the transport of negatively and positively charged colloids in fiberglass wicks. A synthetic pore water solution was used to suspend silica microspheres (330 nm in diameter) and ferrihydrite (172 nm in diameter) for transport experiments on fiberglass wicks. Breakthrough curves were collected for three unsaturated flow rates with silica microspheres and one unsaturated flow rate with ferrihydrite colloids. A moisture characteristic curve, relating tensiometer measurements of matric potential to moisture content, was developed for the fiberglass wick. Results indicate that retention of the silica and the ferrihydrite on the wick occurred; that is, the wicks did not facilitate quantitative sampling of the colloids. For silica microspheres, 90% of the colloids were transmitted through the wicks. For ferrihydrite, 80 to 90% of the colloids were transmitted. The mechanisms responsible for the retention of the colloids on the fiberglass wicks appeared to be physicochemical attachment and not thin-film, triple-phase entrapment, or mechanical straining. Visualization of pathways by iron staining indicates that flow is preferential at the center of twisted bundles of filaments. Although axial preferential flow in PCAPS may enhance their hydraulic suitability for sampling mobile colloids, we conclude that without specific preparation to reduce attachment or retention, fiberglass wicks should only be used for qualitative sampling of pore water colloids.

Quantifying Attachment and Antibiotic Resistance of from Conventional and Organic Swine Manure.

PubMed

Zwonitzer, Martha R; Soupir, Michelle L; Jarboe, Laura R; Smith, Douglas R

2016-03-01

Broad-spectrum antibiotics are often administered to swine, contributing to the occurrence of antibiotic-resistant bacteria in their manure. During land application, the bacteria in swine manure preferentially attach to particles in the soil, affecting their transport in overland flow. However, a quantitative understanding of these attachment mechanisms is lacking, and their relationship to antibiotic resistance is unknown. The objective of this study is to examine the relationships between antibiotic resistance and attachment to very fine silica sand in collected from swine manure. A total of 556 isolates were collected from six farms, two organic and four conventional (antibiotics fed prophylactically). Antibiotic resistance was quantified using 13 antibiotics at three minimum inhibitory concentrations: resistant, intermediate, and susceptible. Of the 556 isolates used in the antibiotic resistance assays, 491 were subjected to an attachment assay. Results show that isolates from conventional systems were significantly more resistant to amoxicillin, ampicillin, chlortetracycline, erythromycin, kanamycin, neomycin, streptomycin, tetracycline, and tylosin ( < 0.001). Results also indicate that isolated from conventional systems attached to very fine silica sand at significantly higher levels than those from organic systems ( < 0.001). Statistical analysis showed that a significant relationship did not exist between antibiotic resistance levels and attachment in from conventional systems but did for organic systems ( < 0.001). Better quantification of these relationships is critical to understanding the behavior of in the environment and preventing exposure of human populations to antibiotic-resistant bacteria. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Attachment dynamics of Photosystem I on nano-tailored surfaces for photovoltaic applications

NASA Astrophysics Data System (ADS)

Mukherjee, Dibyendu; Bruce, Barry D.; Khomami, Bamin

2010-03-01

Photosystem I (PSI), a biological photodiode, is a supra-molecular protein complex that charge separates upon exposure to light. Effective use of photo-electrochemical activities of PSI for hybrid photovoltaic (PV) device fabrications requires optimal encapsulation of these proteins onto organic/ inorganic substrates. Our results indicate that various experimental parameters alter the surface attachment dynamics of PSI deposited from colloidal aqueous buffer suspensions onto OH-terminated alkanethiolate/Au SAM substrates, thereby resulting in complex structural arrangements which affect the electron transfer and capture pathway of PSI. We present surface topographical, specific adsorption and polarization fluorescence characterizations of PSI/Au SAM substrates to elucidate the protein-surface interaction kinetics as well as the directional attachment dynamics of PSI. Our final goal is to enable site-specific homogeneous attachment of directionally aligned PSI onto chemically tailored nano-patterned substrates.

[Sibling relations from the family therapy perspective--support, attachment, rivalry and envy].

PubMed

Cierpka, M

2001-01-01

In family therapy, during the last years more and more importance is attached to the dynamics of the sibling subsystem. In the present paper differences between them as well as similarities are discussed from the point of view of family theory. Relevant dimensions like support, attachment, rivalry and envy between brothers and sisters contribute essentially to the family dynamics. In this clinically orientated paper, we describe by means of a case example how the couple's conflicts after their separation is unconsciously repeated in the sibling subsystem. It is shown how the intergenerational dynamics can be interrupted by the initiative of the children and the initiated family therapy.

Dynamics of dissociative electron attachment to ammonia

DOE PAGES

Rescigno, T. N.; Trevisan, C. S.; Orel, A. E.; ...

2016-05-12

We present that ab initio theoretical studies and momentum-imaging experiments are combined to provide a consistent picture of the dynamics of dissociative electron attachment to ammonia through its 5.5- and 10.5-eV resonance channels. The present study clarifies the character and symmetry of the anion states involved and the dynamics that leads to the observed fragment-ion channels, their branching ratios, and angular distributions.

Dynamics of dissociative electron attachment to ammonia

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

Rescigno, T. N.; Trevisan, C. S.; Orel, A. E.

We present that ab initio theoretical studies and momentum-imaging experiments are combined to provide a consistent picture of the dynamics of dissociative electron attachment to ammonia through its 5.5- and 10.5-eV resonance channels. The present study clarifies the character and symmetry of the anion states involved and the dynamics that leads to the observed fragment-ion channels, their branching ratios, and angular distributions.

Different perspectives on the sex-attachment link: towards an emotion-motivational account.

PubMed

Dewitte, Marieke

2012-01-01

Although the link between sex and attachment was made decades ago (Hazan & Shaver, 1987), theories on sexual and attachment functioning have been developed in relative isolation. Recent efforts to integrate both literatures have been complicated by the fact that the sex-attachment link has been approached from very different perspectives, including biological, evolutionary, developmental, cognitive, and social psychology approaches. Also, at the empirical level, research on sex and attachment lacks overarching synthesis. This article gives an overview of the most important theoretical ideas and empirical insights on sex and attachment. It starts with describing general models that approach the sex-attachment link from an evolutionary and neurobiological perspective. Then, it summarizes theoretical and empirical ideas of attachment theory and describes how attachment style differences are manifested in intimate and sexual relationships. Research so far has been limited to studying the predicted link between sex and attachment in terms of broad descriptives, and it would benefit the literature to specify the processes and pathways that mediate the sex-attachment link. After a short discussion of the functional similarities between the sexual and the attachment systems, the article describes some specific--dynamical--models that focus on the emotional and cognitive-motivational processes through which attachment schemas influence sexual experiences. Such an emotion-motivational perspective on sex and attachment can help to organize theoretical ideas and empirical findings and eventually promote an integrative view on how attachment dynamics can interact with sexual experiences.

Scaling of Topologically Similar Functional Modules Defines Mouse Primary Auditory and Somatosensory Microcircuitry

PubMed Central

Sadovsky, Alexander J.

2013-01-01

Mapping the flow of activity through neocortical microcircuits provides key insights into the underlying circuit architecture. Using a comparative analysis we determined the extent to which the dynamics of microcircuits in mouse primary somatosensory barrel field (S1BF) and auditory (A1) neocortex generalize. We imaged the simultaneous dynamics of up to 1126 neurons spanning multiple columns and layers using high-speed multiphoton imaging. The temporal progression and reliability of reactivation of circuit events in both regions suggested common underlying cortical design features. We used circuit activity flow to generate functional connectivity maps, or graphs, to test the microcircuit hypothesis within a functional framework. S1BF and A1 present a useful test of the postulate as both regions map sensory input anatomically, but each area appears organized according to different design principles. We projected the functional topologies into anatomical space and found benchmarks of organization that had been previously described using physiology and anatomical methods, consistent with a close mapping between anatomy and functional dynamics. By comparing graphs representing activity flow we found that each region is similarly organized as highlighted by hallmarks of small world, scale free, and hierarchical modular topologies. Models of prototypical functional circuits from each area of cortex were sufficient to recapitulate experimentally observed circuit activity. Convergence to common behavior by these models was accomplished using preferential attachment to scale from an auditory up to a somatosensory circuit. These functional data imply that the microcircuit hypothesis be framed as scalable principles of neocortical circuit design. PMID:23986241

Brownian dynamics simulation of fission yeast mitotic spindle formation

NASA Astrophysics Data System (ADS)

Edelmaier, Christopher

2014-03-01

The mitotic spindle segregates chromosomes during mitosis. The dynamics that establish bipolar spindle formation are not well understood. We have developed a computational model of fission-yeast mitotic spindle formation using Brownian dynamics and kinetic Monte Carlo methods. Our model includes rigid, dynamic microtubules, a spherical nuclear envelope, spindle pole bodies anchored in the nuclear envelope, and crosslinkers and crosslinking motor proteins. Crosslinkers and crosslinking motor proteins attach and detach in a grand canonical ensemble, and exert forces and torques on the attached microtubules. We have modeled increased affinity for crosslinking motor attachment to antiparallel microtubule pairs, and stabilization of microtubules in the interpolar bundle. We study parameters controlling the stability of the interpolar bundle and assembly of a bipolar spindle from initially adjacent spindle-pole bodies.

Identifying Dynamic Protein Complexes Based on Gene Expression Profiles and PPI Networks

PubMed Central

Li, Min; Chen, Weijie; Wang, Jianxin; Pan, Yi

2014-01-01

Identification of protein complexes from protein-protein interaction networks has become a key problem for understanding cellular life in postgenomic era. Many computational methods have been proposed for identifying protein complexes. Up to now, the existing computational methods are mostly applied on static PPI networks. However, proteins and their interactions are dynamic in reality. Identifying dynamic protein complexes is more meaningful and challenging. In this paper, a novel algorithm, named DPC, is proposed to identify dynamic protein complexes by integrating PPI data and gene expression profiles. According to Core-Attachment assumption, these proteins which are always active in the molecular cycle are regarded as core proteins. The protein-complex cores are identified from these always active proteins by detecting dense subgraphs. Final protein complexes are extended from the protein-complex cores by adding attachments based on a topological character of “closeness” and dynamic meaning. The protein complexes produced by our algorithm DPC contain two parts: static core expressed in all the molecular cycle and dynamic attachments short-lived. The proposed algorithm DPC was applied on the data of Saccharomyces cerevisiae and the experimental results show that DPC outperforms CMC, MCL, SPICi, HC-PIN, COACH, and Core-Attachment based on the validation of matching with known complexes and hF-measures. PMID:24963481

Preferential sites for InAsP/InP quantum wire nucleation using molecular dynamics

NASA Astrophysics Data System (ADS)

Nuñez-Moraleda, Bernardo; Pizarro, Joaquin; Guerrero, Elisa; Guerrero-Lebrero, Maria P.; Yáñez, Andres; Molina, Sergio Ignacio; Galindo, Pedro Luis

2014-11-01

In this paper, stress fields at the surface of the capping layer of self-assembled InAsP quantum wires grown on an InP (001) substrate have been determined from atomistic models using molecular dynamics and Stillinger-Weber potentials. To carry out these calculations, the quantum wire compositional distribution was extracted from previous works, where the As and P distributions were determined by electron energy loss spectroscopy and high-resolution aberration-corrected Z-contrast imaging. Preferential sites for the nucleation of wires on the surface of the capping layer were studied and compared with (i) previous simulations using finite element analysis to solve anisotropic elastic theory equations and (ii) experimentally measured locations of stacked wires. Preferential nucleation sites of stacked wires were determined by the maximum stress location at the MD model surface in good agreement with experimental results and those derived from finite element analysis. This indicates that MD simulations based on empirical potentials provide a suitable and flexible tool to study strain dependent atom processes.

Applications of Lexical Link Analysis Web Service for Large-Scale Automation, Validation, Discovery, Visualization, and Real-Time Program-Awareness

DTIC Science & Technology

2012-04-30

individualistic , Western view of human behavior. That is, it assumes that people adhere to the individualistic principles of Western culture . What happens to...people with networks rich in structural holes that live/work in environments that adhere to other principles, such as those of a collectivistic ... culture ? •http://orgtheory.wordpress.com/2007/06/19/structural-holes-in-context/ Preferential Attachment (PA) [Barabási & Albert, 1999] • The most

Empirical Determination of Pattern Match Confidence in Labeled Graphs

DTIC Science & Technology

2014-02-07

were explored; Erdős–Rényi [6] random graphs, Barabási–Albert preferential attachment graphs [2], and Watts– Strogatz [18] small world graphs. The ER...B. Erdos - Renyi Barabasi - Albert Gr ap h Ty pe Strogatz - Watts Direct Within 2 nodes Within 4 nodes Search Limit 1 10 100 1000 10000 100000 100...Barabási–Albert (BA, crosses) and Watts– Strogatz (WS, trian- gles) graphs were generated with sizes ranging from 50 to 2500 nodes, and labeled

Competition-Induced Criticality in a Model of Meme Popularity

NASA Astrophysics Data System (ADS)

Gleeson, James P.; Ward, Jonathan A.; O'Sullivan, Kevin P.; Lee, William T.

2014-01-01

Heavy-tailed distributions of meme popularity occur naturally in a model of meme diffusion on social networks. Competition between multiple memes for the limited resource of user attention is identified as the mechanism that poises the system at criticality. The popularity growth of each meme is described by a critical branching process, and asymptotic analysis predicts power-law distributions of popularity with very heavy tails (exponent α <2, unlike preferential-attachment models), similar to those seen in empirical data.

Competition-induced criticality in a model of meme popularity.

PubMed

Gleeson, James P; Ward, Jonathan A; O'Sullivan, Kevin P; Lee, William T

2014-01-31

Heavy-tailed distributions of meme popularity occur naturally in a model of meme diffusion on social networks. Competition between multiple memes for the limited resource of user attention is identified as the mechanism that poises the system at criticality. The popularity growth of each meme is described by a critical branching process, and asymptotic analysis predicts power-law distributions of popularity with very heavy tails (exponent α<2, unlike preferential-attachment models), similar to those seen in empirical data.

A multiscale computational approach to dissect early events in the Erb family receptor mediated activation, differential signaling, and relevance to oncogenic transformations.

PubMed

Liu, Yingting; Purvis, Jeremy; Shih, Andrew; Weinstein, Joshua; Agrawal, Neeraj; Radhakrishnan, Ravi

2007-06-01

We describe a hierarchical multiscale computational approach based on molecular dynamics simulations, free energy-based molecular docking simulations, deterministic network-based kinetic modeling, and hybrid discrete/continuum stochastic dynamics protocols to study the dimer-mediated receptor activation characteristics of the Erb family receptors, specifically the epidermal growth factor receptor (EGFR). Through these modeling approaches, we are able to extend the prior modeling of EGF-mediated signal transduction by considering specific EGFR tyrosine kinase (EGFRTK) docking interactions mediated by differential binding and phosphorylation of different C-terminal peptide tyrosines on the RTK tail. By modeling signal flows through branching pathways of the EGFRTK resolved on a molecular basis, we are able to transcribe the effects of molecular alterations in the receptor (e.g., mutant forms of the receptor) to differing kinetic behavior and downstream signaling response. Our molecular dynamics simulations show that the drug sensitizing mutation (L834R) of EGFR stabilizes the active conformation to make the system constitutively active. Docking simulations show preferential characteristics (for wildtype vs. mutant receptors) in inhibitor binding as well as preferential enhancement of phosphorylation of particular substrate tyrosines over others. We find that in comparison to the wildtype system, the L834R mutant RTK preferentially binds the inhibitor erlotinib, as well as preferentially phosphorylates the substrate tyrosine Y1068 but not Y1173. We predict that these molecular level changes result in preferential activation of the Akt signaling pathway in comparison to the Erk signaling pathway for cells with normal EGFR expression. For cells with EGFR over expression, the mutant over activates both Erk and Akt pathways, in comparison to wildtype. These results are consistent with qualitative experimental measurements reported in the literature. We discuss these consequences in light of how the network topology and signaling characteristics of altered (mutant) cell lines are shaped differently in relationship to native cell lines.

Dynamics and Removal Pathway of Edge Dislocations in Imperfectly Attached PbTe Nanocrystal Pairs: Toward Design Rules for Oriented Attachment.

PubMed

Ondry, Justin C; Hauwiller, Matthew R; Alivisatos, A Paul

2018-04-24

Using in situ high-resolution TEM, we study the structure and dynamics of well-defined edge dislocations in imperfectly attached PbTe nanocrystals. We identify that attachment of PbTe nanocrystals on both {100} and {110} facets gives rise to b = a/2⟨110⟩ edge dislocations. Based on the Burgers vector of individual dislocations, we can identify the glide plane of the dislocations. We observe that defects in particles attached on {100} facets have glide planes that quickly intersect the surface, and HRTEM movies show that the defects follow the glide plane to the surface. For {110} attached particles, the glide plane is collinear with the attachment direction, which does not provide an easy path for the dislocation to reach the surface. Indeed, HRTEM movies of dislocations for {110} attached particles show that defect removal is much slower. Further, we observe conversion from pure edge dislocations in imperfectly attached particles to dislocations with mixed edge and screw character, which has important implications for crystal growth. Finally, we observe that dislocations initially closer to the surface have a higher speed of removal, consistent with the strong dislocation free surface attractive force. Our results provide important design rules for defect-free attachment of preformed nanocrystals into epitaxial assemblies.

Viral Capsid DNA Aptamer Conjugates as Multivalent Cell Targeting Vehicles

PubMed Central

Tong, Gary J.; Hsiao, Sonny C.; Carrico, Zachary M.; Francis, Matthew B.

2009-01-01

Nucleic acid aptamers offer significant potential as convenient and evolvable targeting groups for drug delivery. To attach them to the surface of a genome-free viral capsid carrier, an efficient oxidative coupling strategy has been developed. The method involves the periodate-mediated reaction of phenylene diamine substituted oligonucleotides with aniline groups installed on the outer surface of the capsid shells. Up to 60 DNA strands can be attached to each viral capsid with no apparent loss of base-pairing capabilities or protein stability. The ability of the capsids to bind specific cellular targets was demonstrated through the attachment of a 41-nucleotide sequence that targets a tyrosine kinase receptor on Jurkat T cells. After the installation of a fluorescent dye on the capsid interior, capsids bearing the cell-targeting sequence showed significant levels of binding to the cells relative to control samples. Colocalization experiments using confocal microscopy indicated that the capsids were endocytosed and trafficked to lysosomes for degradation. These observations suggest that aptamer-labeled capsids could be used for the targeted drug delivery of acid-labile prodrugs that would be preferentially released upon lysosomal acidification. PMID:19603808

The lutheran/basal cell adhesion molecule promotes tumor cell migration by modulating integrin-mediated cell attachment to laminin-511 protein.

PubMed

Kikkawa, Yamato; Ogawa, Takaho; Sudo, Ryo; Yamada, Yuji; Katagiri, Fumihiko; Hozumi, Kentaro; Nomizu, Motoyoshi; Miner, Jeffrey H

2013-10-25

Cell-matrix interactions are critical for tumor cell migration. Lutheran (Lu), also known as basal cell adhesion molecule (B-CAM), competes with integrins for binding to laminin α5, a subunit of LM-511, a major component of basement membranes. Here we show that the preferential binding of Lu/B-CAM to laminin α5 promotes tumor cell migration. The attachment of Lu/B-CAM transfectants to LM-511 was slightly weaker than that of control cells, and this was because Lu/B-CAM disturbed integrin binding to laminin α5. Lu/B-CAM induced a spindle cell shape with pseudopods and promoted cell migration on LM-511. In addition, blocking with an anti-Lu/B-CAM antibody led to a flat cell shape and inhibited migration on LM-511, similar to the effects of an activating integrin β1 antibody. We conclude that tumor cell migration on LM-511 requires that Lu/B-CAM competitively modulates cell attachment through integrins. We suggest that this competitive interaction is involved in a balance between static and migratory cell behaviors.

High-Frequency Stimulation of Dorsal Column Axons: Potential Underlying Mechanism of Paresthesia-Free Neuropathic Pain Relief.

PubMed

Arle, Jeffrey E; Mei, Longzhi; Carlson, Kristen W; Shils, Jay L

2016-06-01

Spinal cord stimulation (SCS) treats neuropathic pain through retrograde stimulation of dorsal column axons and their inhibitory effects on wide dynamic range (WDR) neurons. Typical SCS uses frequencies from 50-100 Hz. Newer stimulation paradigms use high-frequency stimulation (HFS) up to 10 kHz and produce pain relief but without paresthesia. Our hypothesis is that HFS preferentially blocks larger diameter axons (12-15 µm) based on dynamics of ion channel gates and the electric potential gradient seen along the axon, resulting in inhibition of WDR cells without paresthesia. We input field potential values from a finite element model of SCS into an active axon model with ion channel subcomponents for fiber diameters 1-20 µm and simulated dynamics on a 0.001 msec time scale. Assuming some degree of wave rectification seen at the axon, action potential (AP) blockade occurs as hypothesized, preferentially in larger over smaller diameters with blockade in most medium and large diameters occurring between 4.5 and 10 kHz. Simulations show both ion channel gate and virtual anode dynamics are necessary. At clinical HFS frequencies and pulse widths, HFS preferentially blocks larger-diameter fibers and concomitantly recruits medium and smaller fibers. These effects are a result of interaction between ion gate dynamics and the "activating function" (AF) deriving from current distribution over the axon. The larger fibers that cause paresthesia in low-frequency simulation are blocked, while medium and smaller fibers are recruited, leading to paresthesia-free neuropathic pain relief by inhibiting WDR cells. © 2016 International Neuromodulation Society.

Novel fragmentation pathways of anionic adducts of steroids formed by electrospray anion attachment involving regioselective attachment, regiospecific decompositions, charge-induced pathways, and ion-dipole complex intermediates.

PubMed

Rannulu, Nalaka S; Cole, Richard B

2012-09-01

The analysis of several bifunctional neutral steroids, 5-α-pregnane diol (5-α-pregnane-3α-20βdiol), estradiol (3,17α-dihydroxy-1,3,5(10)-estratriene), progesterone (4-pregnene-3,20-dione), lupeol (3β-hydroxy-20(29)-lupene), pregnenolone (5-pregnen-3β-ol-20-one), and pregnenolone acetate (5-pregnen-3β-ol-20-one acetate) was accomplished by negative ion electrospray mass spectrometry (ESI-MS) employing adduct formation with various anions: fluoride, bicarbonate, acetate, and chloride. Fluoride yielded higher abundances of anionic adducts and more substantial abundances of deprotonated molecules compared with other investigated anions. Collision-induced dissociation (CID) of precursor [M + anion](-) adducts of these steroids revealed that fluoride adduct [M + F](-) precursors first lose HF to produce [M - H](-) and then undergo consecutive decompositions to yield higher abundances of structurally-informative product ions than the other tested anions. In addition to charge-remote fragmentations, the majority of CID pathways of estradiol are deduced to occur via charge-induced fragmentation. Most interestingly, certain anions exhibit preferential attachment to a specific site on these bifunctional steroid molecules, which we are calling "regioselective anion attachment." Regioselective anion attachment is evidenced by subsequent regiospecific decomposition. Regioselective attachment of fluoride (and acetate) anions to low (and moderate) acidity functional groups of pregnenolone, respectively, is demonstrated using deuterated compounds. Moreover, the formation of unique intermediate ion-dipole complexes leading to novel fragmentation pathways of fluoride adducts of pregnenolone acetate, and bicarbonate adducts of d(4)-pregnenolone, are also discussed.

Novel Fragmentation Pathways of Anionic Adducts of Steroids Formed by Electrospray Anion Attachment Involving Regioselective Attachment, Regiospecific Decompositions, Charge-Induced Pathways, and Ion-Dipole Complex Intermediates

NASA Astrophysics Data System (ADS)

Rannulu, Nalaka S.; Cole, Richard B.

2012-09-01

The analysis of several bifunctional neutral steroids, 5-α-pregnane diol (5-α-pregnane-3α-20βdiol), estradiol (3,17α-dihydroxy-1,3,5(10)-estratriene), progesterone (4-pregnene-3,20-dione), lupeol (3β-hydroxy-20(29)-lupene), pregnenolone (5-pregnen-3β-ol-20-one), and pregnenolone acetate (5-pregnen-3β-ol-20-one acetate) was accomplished by negative ion electrospray mass spectrometry (ESI-MS) employing adduct formation with various anions: fluoride, bicarbonate, acetate, and chloride. Fluoride yielded higher abundances of anionic adducts and more substantial abundances of deprotonated molecules compared with other investigated anions. Collision-induced dissociation (CID) of precursor [M + anion]- adducts of these steroids revealed that fluoride adduct [M + F]- precursors first lose HF to produce [M - H]- and then undergo consecutive decompositions to yield higher abundances of structurally-informative product ions than the other tested anions. In addition to charge-remote fragmentations, the majority of CID pathways of estradiol are deduced to occur via charge-induced fragmentation. Most interestingly, certain anions exhibit preferential attachment to a specific site on these bifunctional steroid molecules, which we are calling "regioselective anion attachment." Regioselective anion attachment is evidenced by subsequent regiospecific decomposition. Regioselective attachment of fluoride (and acetate) anions to low (and moderate) acidity functional groups of pregnenolone, respectively, is demonstrated using deuterated compounds. Moreover, the formation of unique intermediate ion-dipole complexes leading to novel fragmentation pathways of fluoride adducts of pregnenolone acetate, and bicarbonate adducts of d4-pregnenolone, are also discussed.

Community dynamics of attached and free cells and the effects of attached cells on chalcopyrite bioleaching by Acidithiobacillus sp.

PubMed

Yang, Hailin; Feng, Shoushuai; Xin, Yu; Wang, Wu

2014-02-01

The community dynamics of attached and free cells of Acidithiobacillus sp. were investigated and compared during chalcopyrite bioleaching process. In the mixed strains system, Acidithiobacillus ferrooxidans was the dominant species at the early stage while Acidithiobacillus thiooxidans owned competitive advantage from the middle stage to the end of bioprocess. Meanwhile, compared to A. ferrooxidans, more significant effects of attached cells on free biomass with A. thiooxidans were shown in either the pure or mixed strains systems. Moreover, the effects of attached cells on key chemical parameters were also studied in different adsorption-deficient systems. Consistently, the greatest reduction of key chemical ion was shown with A. thiooxidans and the loss of bioleaching efficiency was high to 50.5%. These results all demonstrated the bioleaching function of attached cells was more efficient than the free cells, especially with A. thiooxidans. These notable results would help us to further understand the chalcopyrite bioleaching. Copyright © 2013 Elsevier Ltd. All rights reserved.

Poly(ADP-ribose) polymerases covalently modify strand break termini in DNA fragments in vitro

PubMed Central

Talhaoui, Ibtissam; Lebedeva, Natalia A.; Zarkovic, Gabriella; Saint-Pierre, Christine; Kutuzov, Mikhail M.; Sukhanova, Maria V.; Matkarimov, Bakhyt T.; Gasparutto, Didier; Saparbaev, Murat K.; Lavrik, Olga I.; Ishchenko, Alexander A.

2016-01-01

Poly(ADP-ribose) polymerases (PARPs/ARTDs) use nicotinamide adenine dinucleotide (NAD+) to catalyse the synthesis of a long branched poly(ADP-ribose) polymer (PAR) attached to the acceptor amino acid residues of nuclear proteins. PARPs act on single- and double-stranded DNA breaks by recruiting DNA repair factors. Here, in in vitro biochemical experiments, we found that the mammalian PARP1 and PARP2 proteins can directly ADP-ribosylate the termini of DNA oligonucleotides. PARP1 preferentially catalysed covalent attachment of ADP-ribose units to the ends of recessed DNA duplexes containing 3′-cordycepin, 5′- and 3′-phosphate and also to 5′-phosphate of a single-stranded oligonucleotide. PARP2 preferentially ADP-ribosylated the nicked/gapped DNA duplexes containing 5′-phosphate at the double-stranded termini. PAR glycohydrolase (PARG) restored native DNA structure by hydrolysing PAR-DNA adducts generated by PARP1 and PARP2. Biochemical and mass spectrometry analyses of the adducts suggested that PARPs utilise DNA termini as an alternative to 2′-hydroxyl of ADP-ribose and protein acceptor residues to catalyse PAR chain initiation either via the 2′,1″-O-glycosidic ribose-ribose bond or via phosphodiester bond formation between C1′ of ADP-ribose and the phosphate of a terminal deoxyribonucleotide. This new type of post-replicative modification of DNA provides novel insights into the molecular mechanisms underlying biological phenomena of ADP-ribosylation mediated by PARPs. PMID:27471034

An exploration of family dynamics and attachment strategies in a family with ADHD/conduct problems.

PubMed

Dallos, Rudi; Smart, Cordet

2011-10-01

This article reports the preliminary findings of a study of attachment patterns and relationship themes using the TAAI (Transition to Adulthood Attachment Interview), AAI (Adult Attachment Interview) and family interviews (based on the first of 15 families). Research data is presented on a young man aged 16 with a diagnosis of ADHD and his family. Individual interviews, attachment interviews, and family interviews were conducted in order to explore the link between family dynamics, ADHD and attachment strategies. In contrast to findings from existing research indicating pre-occupied patterns for young people diagnosed with ADHD, the young man displayed a complex 'disoriented' attachment pattern which primarily featured a dismissive strategy. However, this was combined with pre-occupied patterns triggered by intrusions from unresolved traumas and memories of his parents' continuing unresolved conflicts. His sense of confusion and lack of a coherent strategy appeared to be closely related to his position of being triangulated into his parents' conflicts. Trans-generational processes were also influential, in that the parents' corrective intentions at more positive parenting were impeded by their own lack of experience of positive attachments in their own childhoods. The study emphasizes the need to consider the relationship between attachment patterns and problems within wider systemic process in the family, in particular triangulation and corrective scripts.

Use of soil moisture dynamics and patterns for the investigation of runoff generation processes with emphasis on preferential flow

NASA Astrophysics Data System (ADS)

Blume, T.; Zehe, E.; Bronstert, A.

2007-08-01

Spatial patterns as well as temporal dynamics of soil moisture have a major influence on runoff generation. The investigation of these dynamics and patterns can thus yield valuable information on hydrological processes, especially in data scarce or previously ungauged catchments. The combination of spatially scarce but temporally high resolution soil moisture profiles with episodic and thus temporally scarce moisture profiles at additional locations provides information on spatial as well as temporal patterns of soil moisture at the hillslope transect scale. This approach is better suited to difficult terrain (dense forest, steep slopes) than geophysical techniques and at the same time less cost-intensive than a high resolution grid of continuously measuring sensors. Rainfall simulation experiments with dye tracers while continuously monitoring soil moisture response allows for visualization of flow processes in the unsaturated zone at these locations. Data was analyzed at different spacio-temporal scales using various graphical methods, such as space-time colour maps (for the event and plot scale) and indicator maps (for the long-term and hillslope scale). Annual dynamics of soil moisture and decimeter-scale variability were also investigated. The proposed approach proved to be successful in the investigation of flow processes in the unsaturated zone and showed the importance of preferential flow in the Malalcahuello Catchment, a data-scarce catchment in the Andes of Southern Chile. Fast response times of stream flow indicate that preferential flow observed at the plot scale might also be of importance at the hillslope or catchment scale. Flow patterns were highly variable in space but persistent in time. The most likely explanation for preferential flow in this catchment is a combination of hydrophobicity, small scale heterogeneity in rainfall due to redistribution in the canopy and strong gradients in unsaturated conductivities leading to self-reinforcing flow paths.

Small-world network model of propagation of the AIDS epidemic

NASA Astrophysics Data System (ADS)

Shi, Pengliang; Small, Michael

2004-03-01

Sexual contact and intravenus drug-use are the most common modes of transmission of HIV-AIDS. In this paper, homogenerous and heterogeneous models are proposed to model the dynamics in a system contains Small-World clusters. Four high risk groups: intravenus drug-users (D); homosexuals (H); individuals with multiple-sexual partners (M) and prostitutes (P), are classified using two models. Both networks are embedded among a background (low-risk) population using rich-get-richer preferential attachment. When a network is established, an epidemic is simulated in it by seeding randomly. We compare the two epidemic networks in detail and consider the effect of different levels of control policies in both. This study highlights two main conclusions: (i) set high protection coefficient for a massive-linkage-vertex (i.e. protect the highly connected individuals); and, (ii) a quick removal for the infected massive-linkage-veterx from the network is essential (rapidly quarantine infected individuals). While these conclusions may be intuitive, they indicate a necessary change of public policy toward prostitution in some developing countries such as China and India. An active effort to prevent possible infection from super-spreader is recommended.

Information dynamics shape the sexual networks of Internet-mediated prostitution

PubMed Central

Rocha, Luis E. C.; Liljeros, Fredrik; Holme, Petter

2010-01-01

Like many other social phenomena, prostitution is increasingly coordinated over the Internet. The online behavior affects the offline activity; the reverse is also true. We investigated the reported sexual contacts between 6,624 anonymous escorts and 10,106 sex buyers extracted from an online community from its beginning and six years on. These sexual encounters were also graded and categorized (in terms of the type of sexual activities performed) by the buyers. From the temporal, bipartite network of posts, we found a full feedback loop in which high grades on previous posts affect the future commercial success of the sex worker, and vice versa. We also found a peculiar growth pattern in which the turnover of community members and sex workers causes a sublinear preferential attachment. There is, moreover, a strong geographic influence on network structure—the network is geographically clustered but still close to connected, the contacts consistent with the inverse-square law observed in trading patterns. We also found that the number of sellers scales sublinearly with city size, so this type of prostitution does not, comparatively speaking, benefit much from an increasing concentration of people. PMID:20231480

Competing Classical and Quantum Effects in Shape Relaxation of a Metallic Nanostructure

NASA Technical Reports Server (NTRS)

Chen, Dongmin; Okamoto, Hiroshi; Yamada, Toshishi; Biegel, Bryan (Technical Monitor)

2003-01-01

We demonstrate for the first time that the quantum size effect (QSE) plays a competing role along side the classical thermodynamic effect in the shape relaxation of a small metallic island. Together, these effects transforms a lead(Pb) island grown on Si(111) substrate from its initially flattop faceted morphology to a peculiar ring-shape island, a process catalysed by the tip electric field of a scanning tunnelling microscope (STM). We shall show for the first time how QSE affects the relaxation process dynamically. In particular, it leads to a novel strip-flow growth and double-step growth on selective strips of a plateau inside the ring, defined by the substrate steps more than 60?0?3 below. It appears that atoms diffusing on the plateau can clearly (sub i)(deg)sense(sub i)+/- the quantized energy states inside the island and have preferentially attached to regions that further reduces the surface energy as a result of the QSE, limiting its own growth and stabilizing the ring shape. The mechanism proposed here offers a sound explanation for ring shape metal and semiconductor islands observed in other systems as well.

An evolving model for the lodging-service network in a tourism destination

NASA Astrophysics Data System (ADS)

Hernández, Juan M.; González-Martel, Christian

2017-09-01

Tourism is a complex dynamic system including multiple actors which are related each other composing an evolving social network. This paper presents a growing model that explains how part of the supply components in a tourism system forms a social network. Specifically, the lodgings and services in a destination are the network nodes and a link between them appears if a representative tourist hosted in the lodging visits/consumes the service during his/her stay. The specific link between both categories are determined by a random and preferential attachment rule. The analytic results show that the long-term degree distribution of services follows a shifted power-law distribution. The numerical simulations show slight disagreements with the theoretical results in the case of the one-mode degree distribution of services, due to the low order of convergence to zero of X-motifs. The model predictions are compared with real data coming from a popular tourist destination in Gran Canaria, Spain, showing a good agreement between analytical and empirical data for the degree distribution of services. The theoretical model was validated assuming four type of perturbations in the real data.

Molecular Mechanisms That Underlie the Dynamic Adaptation of Innate Monocyte Memory to Varying Stimulant Strength of TLR Ligands.

PubMed

Yuan, Ruoxi; Geng, Shuo; Li, Liwu

2016-01-01

In adaptation to rising stimulant strength, innate monocytes can be dynamically programed to preferentially express either pro- or anti-inflammatory mediators. Such dynamic innate adaptation or programing may bear profound relevance in host health and disease. However, molecular mechanisms that govern innate adaptation to varying strength of stimulants are not well understood. Using lipopolysaccharide (LPS), the model stimulant of toll-like-receptor 4 (TLR4), we reported that the expressions of pro-inflammatory mediators are preferentially sustained in monocytes adapted by lower doses of LPS, and suppressed/tolerized in monocytes adapted by higher doses of LPS. Mechanistically, monocytes adapted by super-low dose LPS exhibited higher levels of transcription factor, interferon regulatory factor 5 (IRF5), and reduced levels of transcriptional modulator B lymphocyte-induced maturation protein-1 (Blimp-1). Intriguingly, the inflammatory monocyte adaptation by super-low dose LPS is dependent upon TRAM/TRIF but not MyD88. Similar to LPS, we also observed biphasic inflammatory adaptation and tolerance in monocytes challenged with varying dosages of TLR7 agonist. In sharp contrast, rising doses of TLR3 agonist preferentially caused inflammatory adaptation without inducing tolerance. At the molecular level, the differential regulation of IRF5 and Blimp-1 coincides with unique monocyte adaptation dynamics by TLR4/7 and TLR3 agonists. Our study provides novel clue toward the understanding of monocyte adaptation and memory toward distinct TLR ligands.

Application of Attachment Theory to the Study of Sexual Abuse.

ERIC Educational Resources Information Center

Alexander, Pamela C.

1992-01-01

Attachment theory provides useful conceptual framework for understanding familial antecedents and long-term consequences of sexual abuse. Themes associated with insecure parent-child attachment (rejection, role reversal/parentification, and fear/unresolved trauma) are frequently found in dynamics of families characterized by sexual abuse, and…

Reorientation Motion and Preferential Interactions of a Peptide in Denaturants and Osmolyte.

PubMed

Jas, Gouri S; Rentchler, Eric C; Słowicka, Agnieszka M; Hermansen, John R; Johnson, Carey K; Middaugh, C Russell; Kuczera, Krzysztof

2016-03-31

Fluorescence anisotropy decay measurements and all atom molecular dynamics simulations are used to characterize the orientational motion and preferential interaction of a peptide, N-acetyl-tryptophan-amide (NATA) containing two peptide bonds, in aqueous, urea, guanidinium chloride (GdmCl), and proline solution. Anisotropy decay measurements as a function of temperature and concentration showed moderate slowing of reorientations in urea and GdmCl and very strong slowing in proline solution, relative to water. These effects deviate significantly from simple proportionality of peptide tumbling time to solvent viscosity, leading to the investigation of microscopic preferential interaction behavior through molecular dynamics simulations. Examination of the interactions of denaturants and osmolyte with the peptide backbone uncovers the presence of strongest interaction with urea, intermediate with proline, and weakest with GdmCl. In contrast, the strongest preferential solvation of the peptide side chain is by the nonpolar part of the proline zwitterion, followed by urea, and GdmCl. Interestingly, the local density of urea around the side chain is higher, but the GdmCl distribution is more organized. Thus, the computed preferential solvation of the side chain by the denaturants and osmolyte can account for the trend in reorientation rates. Analysis of water structure and its dynamics uncovered underlying differences between urea, GdmCl, and proline. Urea exerted the smallest perturbation of water behavior. GdmCl had a larger effect on water, slowing kinetics and stabilizing interactions. Proline had the largest overall interactions, exhibiting a strong stabilizing effect on both water-water and water-peptide hydrogen bonds. The results for this elementary peptide system demonstrate significant differences in microscopic behavior of the examined solvent environments. For the commonly used denaturants, urea tends to form disorganized local aggregates around the peptide groups and has little influence on water, while GdmCl only forms specific interactions with the side chain and tends to destabilize water structure. The protective osmolyte proline has the strongest and most specific interactions with the tryptophan side chain, and also stabilizes both water-water and water-peptide hydrogen bonds. Our results strongly suggest protein or peptide denaturation triggered by urea occurs by direct interaction, whereas GdmCl interacts favorably with side chains and destabilizes peptide-water hydrogen bonds. The stabilization of biopolymers by an osmolyte such as proline is governed by favorable preferential interaction with the side chains and stabilization of water.

Propellant grain dynamics in aft attach ring of shuttle solid rocket booster

NASA Technical Reports Server (NTRS)

Verderaime, V.

1979-01-01

An analytical technique for implementing simultaneously the temperature, dynamic strain, real modulus, and frequency properties of solid propellant in an unsymmetrical vibrating ring mode is presented. All dynamic parameters and sources are defined for a free vibrating ring-grain structure with initial displacement and related to a forced vibrating system to determine the change in real modulus. Propellant test data application is discussed. The technique was developed to determine the aft attach ring stiffness of the shuttle booster at lift-off.

Electron driven processes in sulphur containing compounds CH3SCH3 and CH3SSCH3

NASA Astrophysics Data System (ADS)

Kopyra, Janina; Władziński, Jakub

2015-06-01

Dissociative electron attachment to gas phase dimethyl sulphide (CH3SCH3) and dimethyl disulphide (CH3SSCH3) has been studied by means of a crossed beams apparatus. Cleavage of the C-S bond within CH3SCH3 and the S-S bond within CH3SSCH3 is observed within a resonance in the energy range below 2 eV and visible preferentially via the appearance of the fragment CH2S-. The striking finding is that the intensity of CH2S- generated from CH3SSCH3 is more than two orders of magnitude higher than the intensity of the respective anionic fragment generated from CH3SCH3. Our results clearly demonstrate that the CH3SSCH3 molecule, which contains disulphide bridge is substantially more sensitive towards electron attachment resulting mainly in dissociation along the S-S bridge.

Preliminary evaluation of the effect of a dynamic preferential runway system upon community noise disturbance

NASA Technical Reports Server (NTRS)

Patterson, H. P.; Edmiston, R. P.; Connor, W. K.

1972-01-01

A dynamic preferential runway system (DPRS) was developed for John F. Kennedy International Airport for the purpose of controlling short term noise exposure in the neighboring communities. The DPRS is a computer-aided procedure for optimum selection of runways from the standpoint of noise and is based upon a community disturbance model which takes into account flyover levels, size of exposed populations, time of day and week, and persistence of overflights. A preliminary evaluation of the DPRS is presented on the basis of social survey data and telephone complaint records, for the trial period of August and September, 1971. Comparative use is made of data taken in a previous survey of the same community areas in 1969.

Effects of individual popularity on information spreading in complex networks

NASA Astrophysics Data System (ADS)

Gao, Lei; Li, Ruiqi; Shu, Panpan; Wang, Wei; Gao, Hui; Cai, Shimin

2018-01-01

In real world, human activities often exhibit preferential selection mechanism based on the popularity of individuals. However, this mechanism is seldom taken into account by previous studies about spreading dynamics on networks. Thus in this work, an information spreading model is proposed by considering the preferential selection based on individuals' current popularity, which is defined as the number of individuals' cumulative contacts with informed neighbors. A mean-field theory is developed to analyze the spreading model. Through systematically studying the information spreading dynamics on uncorrelated configuration networks as well as real-world networks, we find that the popularity preference has great impacts on the information spreading. On the one hand, the information spreading is facilitated, i.e., a larger final prevalence of information and a smaller outbreak threshold, if nodes with low popularity are preferentially selected. In this situation, the effective contacts between informed nodes and susceptible nodes are increased, and nodes almost have uniform probabilities of obtaining the information. On the other hand, if nodes with high popularity are preferentially selected, the final prevalence of information is reduced, the outbreak threshold is increased, and even the information cannot outbreak. In addition, the heterogeneity of the degree distribution and the structure of real-world networks do not qualitatively affect the results. Our research can provide some theoretical supports for the promotion of spreading such as information, health related behaviors, and new products, etc.

Human Ska complex and Ndc80 complex interact to form a load-bearing assembly that strengthens kinetochore–microtubule attachments

PubMed Central

Zelter, Alex; Riffle, Michael; MacCoss, Michael J.; Asbury, Charles L.; Davis, Trisha N.

2018-01-01

Accurate segregation of chromosomes relies on the force-bearing capabilities of the kinetochore to robustly attach chromosomes to dynamic microtubule tips. The human Ska complex and Ndc80 complex are outer-kinetochore components that bind microtubules and are required to fully stabilize kinetochore–microtubule attachments in vivo. While purified Ska complex tracks with disassembling microtubule tips, it remains unclear whether the Ska complex–microtubule interaction is sufficiently strong to make a significant contribution to kinetochore–microtubule coupling. Alternatively, Ska complex might affect kinetochore coupling indirectly, through recruitment of phosphoregulatory factors. Using optical tweezers, we show that the Ska complex itself bears load on microtubule tips, strengthens Ndc80 complex-based tip attachments, and increases the switching dynamics of the attached microtubule tips. Cross-linking mass spectrometry suggests the Ska complex directly binds Ndc80 complex through interactions between the Ska3 unstructured C-terminal region and the coiled-coil regions of each Ndc80 complex subunit. Deletion of the Ska complex microtubule-binding domain or the Ska3 C terminus prevents Ska complex from strengthening Ndc80 complex-based attachments. Together, our results indicate that the Ska complex can directly strengthen the kinetochore–microtubule interface and regulate microtubule tip dynamics by forming an additional connection between the Ndc80 complex and the microtubule. PMID:29487209

Dipole-Guided Electron Capture Causes Abnormal Dissociations of Phosphorylated Pentapeptides

NASA Astrophysics Data System (ADS)

Moss, Christopher L.; Chung, Thomas W.; Wyer, Jean A.; Nielsen, Steen Brøndsted; Hvelplund, Preben; Tureček, František

2011-04-01

Electron transfer and capture mass spectra of a series of doubly charged ions that were phosphorylated pentapeptides of a tryptic type (pS,A,A,A,R) showed conspicuous differences in dissociations of charge-reduced ions. Electron transfer from both gaseous cesium atoms at 100 keV kinetic energies and fluoranthene anion radicals in an ion trap resulted in the loss of a hydrogen atom, ammonia, and backbone cleavages forming complete series of sequence z ions. Elimination of phosphoric acid was negligible. In contrast, capture of low-energy electrons by doubly charged ions in a Penning ion trap induced loss of a hydrogen atom followed by elimination of phosphoric acid as the dominant dissociation channel. Backbone dissociations of charge-reduced ions also occurred but were accompanied by extensive fragmentation of the primary products. z-Ions that were terminated with a deaminated phosphoserine radical competitively eliminated phosphoric acid and H2PO4 radicals. A mechanism is proposed for this novel dissociation on the basis of a computational analysis of reaction pathways and transition states. Electronic structure theory calculations in combination with extensive molecular dynamics mapping of the potential energy surface provided structures for the precursor phosphopeptide dications. Electron attachment produces a multitude of low lying electronic states in charge-reduced ions that determine their reactivity in backbone dissociations and H- atom loss. The predominant loss of H atoms in ECD is explained by a distortion of the Rydberg orbital space by the strong dipolar field of the peptide dication framework. The dipolar field steers the incoming electron to preferentially attach to the positively charged arginine side chain to form guanidinium radicals and trigger their dissociations.

In situ localization of nucleolin in the plant nucleolar matrix.

PubMed

Minguez, A; Moreno Diaz de la Espina, S

1996-01-10

The analysis of isolated nucleolar matrices from onion cells by light and electron microscopy, 2-D separation of proteins, and confocal microscopy has confirmed the existence of an organized nucleolar matrix with a complex protein composition to which are attached the insoluble processing complexes. In the present work, we present evidence from immunoblotting, immunofluorescence, immunogold labeling, and preferential cytochemical staining with bismuth salts that an insoluble fraction of the multifunctional protein nucleolin, is a component of the onion nucleolar matrix, and analyse its ultrastructural distribution in the described domains of the matrix.

Incorporation of Deoxyribonucleic Acid Precursors by T4 Deoxyribonucleic Acid-Protein Complexes Retained on Glass Fiber Filters

PubMed Central

Miller, Robert C.; Kozinski, Andrzej W.

1970-01-01

Bacteriophage T4 deoxyribonucleic acid (DNA)-protein complexes were retained preferentially on glass fiber filters. DNA polymerase activity in the complex was detected through the incorporation of 3H-labeled DNA precursors. The primer-product DNA hybridized with both phage and Escherichia coli DNA. Density labeling experiments showed that about 30% of incorporated 3H-deoxyadenosine triphosphate was found in DNA which hybridized with phage DNA; this DNA was found to be covalently attached to the primer DNA. PMID:5497903

Structural Preferential Attachment: Network Organization beyond the Link

NASA Astrophysics Data System (ADS)

Hébert-Dufresne, Laurent; Allard, Antoine; Marceau, Vincent; Noël, Pierre-André; Dubé, Louis J.

2011-10-01

We introduce a mechanism which models the emergence of the universal properties of complex networks, such as scale independence, modularity and self-similarity, and unifies them under a scale-free organization beyond the link. This brings a new perspective on network organization where communities, instead of links, are the fundamental building blocks of complex systems. We show how our simple model can reproduce social and information networks by predicting their community structure and more importantly, how their nodes or communities are interconnected, often in a self-similar manner.

Optrode for sensing hydrocarbons

DOEpatents

Miller, Holly; Milanovich, Fred P.; Hirschfeld, Tomas B.; Miller, Fred S.

1987-01-01

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons.

Optrode for sensing hydrocarbons

DOEpatents

Miller, H.; Milanovich, F.P.; Hirschfeld, T.B.; Miller, F.S.

1987-05-19

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons. 6 figs.

Optrode for sensing hydrocarbons

DOEpatents

Miller, H.; Milanovich, F.P.; Hirschfeld, T.B.; Miller, F.S.

1988-09-13

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons. 5 figs.

Optrode for sensing hydrocarbons

DOEpatents

Miller, Holly; Milanovich, Fred P.; Hirschfeld, Tomas B.; Miller, Fred S.

1988-01-01

A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons.

Beginnings and Endings in Social Work Supervision: The Interaction between Attachment and Developmental Processes

ERIC Educational Resources Information Center

Bennett, Susanne; Deal, Kathleen Holtz

2009-01-01

This article discusses the interaction of attachment processes and stages of social work student development within the field supervisory relationship and suggests ways supervisors can modify interactions with students. Attachment theory and research provide a framework for understanding innate capacities of students and the relational dynamics of…

Active and Passive Radiative Transfer Modeling with Preferentially-Aligned Particles

NASA Technical Reports Server (NTRS)

Adams, Ian Stuart

2017-01-01

The fluid dynamics of falling hydrometeors often results in preferential orientations that can affect both the intensity and polarization of electromagnetic radiation. In order to properly interpret remote sensing observations of ice and snow, such alignments should be considered when constructing databases of scattering particles; however, the inclusion of aligned particles increases the complexity of the scattering data. To demonstrate the use of scattering properties of preferentially-aligned particles, millimeter-wave brightness temperatures and radar observables, including reflectivity and linear depolarization ratio, are modeled using the Atmospheric Radiative Transfer Simulator (ARTS). The necessary scattering parameters for vector radiative transfer, particularly with respect to ARTS, are reviewed, and the exploitation of particle symmetries, as well as scattering reciprocity relationships, are detailed.

The Effects of Grain Size and Texture on Dynamic Abnormal Grain Growth in Mo

NASA Astrophysics Data System (ADS)

Noell, Philip J.; Taleff, Eric M.

2016-10-01

This is the first report of abnormal grain morphologies specific to a Mo sheet material produced from a commercial-purity arc-melted ingot. Abnormal grains initiated and grew during plastic deformation of this material at temperatures of 1793 K and 1813 K (1520 °C and 1540 °C). This abnormal grain growth during high-temperature plastic deformation is termed dynamic abnormal grain growth, DAGG. DAGG in this material readily consumes nearly all grains near the sheet center while leaving many grains near the sheet surface unconsumed. Crystallographic texture, grain size, and other microstructural features are characterized. After recrystallization, a significant through-thickness variation in crystallographic texture exists in this material but does not appear to directly influence DAGG propagation. Instead, dynamic normal grain growth, which may be influenced by texture, preferentially occurs near the sheet surface prior to DAGG. The large grains thus produced near the sheet surface inhibit the subsequent growth of the abnormal grains produced by DAGG, which preferentially consume the finer grains near the sheet center. This produces abnormal grains that span the sheet center but leave unconsumed polycrystalline microstructure near the sheet surface. Abnormal grains are preferentially oriented with the < 110rangle approximately along the tensile axis. These results provide additional new evidence that boundary curvature is the primary driving force for DAGG in Mo.

Intrinsic Nucleic Acid Dynamics Modulates HIV-1 Nucleocapsid Protein Binding to Its Targets

PubMed Central

Bazzi, Ali; Zargarian, Loussiné; Chaminade, Françoise; De Rocquigny, Hugues; René, Brigitte; Mély, Yves; Fossé, Philippe; Mauffret, Olivier

2012-01-01

HIV-1 nucleocapsid protein (NC) is involved in the rearrangement of nucleic acids occurring in key steps of reverse transcription. The protein, through its two zinc fingers, interacts preferentially with unpaired guanines in single-stranded sequences. In mini-cTAR stem-loop, which corresponds to the top half of the cDNA copy of the transactivation response element of the HIV-1 genome, NC was found to exhibit a clear preference for the TGG sequence at the bottom of mini-cTAR stem. To further understand how this site was selected among several potential binding sites containing unpaired guanines, we probed the intrinsic dynamics of mini-cTAR using 13C relaxation measurements. Results of spin relaxation time measurements have been analyzed using the model-free formalism and completed by dispersion relaxation measurements. Our data indicate that the preferentially recognized guanine in the lower part of the stem is exempt of conformational exchange and highly mobile. In contrast, the unrecognized unpaired guanines of mini-cTAR are involved in conformational exchange, probably related to transient base-pairs. These findings support the notion that NC preferentially recognizes unpaired guanines exhibiting a high degree of mobility. The ability of NC to discriminate between close sequences through their dynamic properties contributes to understanding how NC recognizes specific sites within the HIV genome. PMID:22745685

Identifying attachment ruptures underlying severe music performance anxiety in a professional musician undertaking an assessment and trial therapy of Intensive Short-Term Dynamic Psychotherapy (ISTDP).

PubMed

Kenny, Dianna T; Arthey, Stephen; Abbass, Allan

2016-01-01

Kenny has proposed that severe music performance anxiety that is unresponsive to usual treatments such as cognitive-behaviour therapy may be one manifestation of unresolved attachment ruptures in early life. Intensive Short-Term Dynamic Psychotherapy specifically targets early relationship trauma. Accordingly, a trial of Intensive Short-Term Dynamic Psychotherapy with severely anxious musicians was implemented to assess whether resolution of attachment ruptures resulted in clinically significant relief from music performance anxiety. Volunteer musicians participating in a nationally funded study were screened for MPA severity. Those meeting the critical cut-off score on the Kenny Music Performance Anxiety Inventory were offered a trial of Intensive Short-Term Dynamic Psychotherapy. In this paper, we present the theoretical foundations and rationale for the treatment approach, followed by sections of a verbatim transcript and process analysis of the assessment phase of treatment that comprised a 3-h trial therapy session. The 'case' was a professional orchestral musician (male, aged 55) who had suffered severe music performance anxiety over the course of his entire career, which spanned more than 30 years at the time he presented for treatment following his failure to secure a position at audition. The participant was able to access the pain, rage and grief associated with unresolved attachment ruptures with both parents that demonstrated the likely nexus between early attachment trauma and severe music performance anxiety. Intensive Short-Term Dynamic Psychotherapy is a potentially cost-effective treatment for severe music performance anxiety. Further research using designs with higher levels of evidence are required before clinical recommendations can be made for the use of this therapy with this population.

Inhibition and enhancement of microbial surface colonization: the role of silicate composition

USGS Publications Warehouse

Roberts, Jennifer A.

2004-01-01

Classical treatment of cell attachment by models of filtration or coulombic attraction assumes that attachment of cells to mineral surfaces would be controlled by factors such as response to predation, collision efficiency, or coulombic attraction between the charged groups at the mineral and cell surfaces. In the study reported here, the passive model of attachment was investigated using a native microbial consortium and a variety of Al- and Fe-bearing silicates and oxides to determine if other controls, such as mineral composition, also influence the interaction between cells and surfaces. Results from in situ colonization studies in an anaerobic groundwater at pH 6.8 combined with most probable number analyses (MPN) of surface-adherent cells demonstrate that electrostatic effects dominate microbial colonization on positively charged oxide surfaces regardless of mineral composition. In contrast, on negatively charged silicate minerals and glasses, the solid phase composition is a factor in determining the extent of microbial colonization, as well as the diversity of the attached community. In particular, silicates containing more than 1.2% Al exhibit less biomass than Al-poor silicates and MPN suggests a shift in community diversity, possibly indicating Al toxicity on these surfaces. When Fe is present in the silicate, however, this trend is reversed and abundant colonization of the surface is observed. Here, microorganisms preferentially colonize those silicate surfaces that offer beneficial nutrients and avoid those that contain potentially toxic elements.

Attachment of Pathogenic Prion Protein to Model Oxide Surfaces

PubMed Central

Jacobson, Kurt H.; Kuech, Thomas R.; Pedersen, Joel A.

2014-01-01

Prions are the infectious agents in the class of fatal neurodegenerative diseases known as transmissible spongiform encephalopathies, which affect humans, deer, sheep, and cattle. Prion diseases of deer and sheep can be transmitted via environmental routes, and soil is has been implicated in the transmission of these diseases. Interaction with soil particles is expected to govern the transport, bioavailability and persistence of prions in soil environments. A mechanistic understanding of prion interaction with soil components is critical for understanding the behavior of these proteins in the environment. Here, we report results of a study to investigate the interactions of prions with model oxide surfaces (Al2O3, SiO2) using quartz crystal microbalance with dissipation monitoring and optical waveguide light mode spectroscopy. The efficiency of prion attachment to Al2O3 and SiO2 depended strongly on pH and ionic strength in a manner consistent with electrostatic forces dominating interaction with these oxides. The N-terminal portion of the protein appeared to facilitate attachment to Al2O3 under globally electrostatically repulsive conditions. We evaluated the utility of recombinant prion protein as a surrogate for prions in attachment experiments and found that its behavior differed markedly from that of the infectious agent. Our findings suggest that prions preferentially associate with positively charged mineral surfaces in soils (e.g., iron and aluminum oxides). PMID:23611152

Dissociative electron attachments to ethanol and acetaldehyde: A combined experimental and simulation study

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

Wang, Xu-Dong; Xuan, Chuan-Jin; Feng, Wen-Ling

Dissociation dynamics of the temporary negative ions of ethanol and acetaldehyde formed by the low-energy electron attachments is investigated by using the anion velocity map imaging technique and ab initio molecular dynamics simulations. The momentum images of the dominant fragments O{sup −}/OH{sup −} and CH{sub 3}{sup −} are recorded, indicating the low kinetic energies of O{sup −}/OH{sup −} for ethanol while the low and high kinetic energy distributions of O{sup −} ions for acetaldehyde. The CH{sub 3}{sup −} image for acetaldehyde also shows the low kinetic energy. With help of the dynamics simulations, the fragmentation processes are qualitatively clarified. Amore » new cascade dissociation pathway to produce the slow O{sup −} ion via the dehydrogenated intermediate, CH{sub 3}CHO{sup −} (acetaldehyde anion), is proposed for the dissociative electron attachment to ethanol. After the electron attachment to acetaldehyde molecule, the slow CH{sub 3}{sup −} is produced quickly in the two-body dissociation with the internal energy redistributions in different aspects before bond cleavages.« less

Links between Risk and Attachment Security: Models of Influence

ERIC Educational Resources Information Center

Raikes, H. Abigail; Thompson, Ross A.

2005-01-01

The relation between maternal behavior and child attachment security is weaker among low SES samples, but it is unclear how stressors/risks associated with low SES alter the dynamics of attachment relationships. Results of this study of 63 low income mothers and their 24-36-month-old children indicated that the influence of multiple economic risks…

A paradigm for viewing biologic systems as scale-free networks based on energy efficiency: implications for present therapies and the future of evolution.

PubMed

Yun, Anthony J; Lee, Patrick Y; Doux, John D

2006-01-01

A network constitutes an abstract description of the relationships among entities, respectively termed links and nodes. If a power law describes the probability distribution of the number of links per node, the network is said to be scale-free. Scale-free networks feature link clustering around certain hubs based on preferential attachments that emerge due either to merit or legacy. Biologic systems ranging from sub-atomic to ecosystems represent scale-free networks in which energy efficiency forms the basis of preferential attachments. This paradigm engenders a novel scale-free network theory of evolution based on energy efficiency. As environmental flux induces fitness dislocations and compels a new meritocracy, new merit-based hubs emerge, previously merit-based hubs become legacy hubs, and network recalibration occurs to achieve system optimization. To date, Darwinian evolution, characterized by innovation sampling, variation, and selection through filtered termination, has enabled biologic progress through optimization of energy efficiency. However, as humans remodel their environment, increasing the level of unanticipated fitness dislocations and inducing evolutionary stress, the tendency of networks to exhibit inertia and retain legacy hubs engender maladaptations. Many modern diseases may fundamentally derive from these evolutionary displacements. Death itself may constitute a programmed adaptation, terminating individuals who represent legacy hubs and recalibrating the network. As memes replace genes as the basis of innovation, death itself has become a legacy hub. Post-Darwinian evolution may favor indefinite persistence to optimize energy efficiency. We describe strategies to reprogram or decommission legacy hubs that participate in human disease and death.

Preferential location of lidocaine and etidocaine in lecithin bilayers as determined by EPR, fluorescence and 2H NMR.

PubMed

de Paula, Eneida; Schreier, Shirley; Jarrell, Harold C; Fraceto, Leonardo Fernandes

2008-01-01

We have examined the effect of the uncharged species of lidocaine (LDC) and etidocaine (EDC) on the acyl chain moiety of egg phosphatidylcholine liposomes. Changes in membrane organization caused by both anesthetics were detected through the use of EPR spin labels (5, 7 and 12 doxyl stearic acid methyl ester) or fluorescence probes (4, 6, 10, 16 pyrene-fatty acids). The disturbance caused by the LA was greater when the probes were inserted in more external positions of the acyl chain and decreased towards the hydrophobic core of the membrane. The results indicate a preferential insertion of LDC at the polar interface of the bilayer and in the first half of the acyl chain, for EDC. Additionally, (2)H NMR spectra of multilamellar liposomes composed by acyl chain-perdeutero DMPC and EPC (1:4 mol%) allowed the determination of the segmental order (S(mol)) and dynamics (T(1)) of the acyl chain region. In accordance to the fluorescence and EPR results, changes in molecular orientation and dynamics are more prominent if the LA preferential location is more superficial, as for LDC while EDC seems to organize the acyl chain region between carbons 2-8, which is indicative of its positioning. We propose that the preferential location of LDC and EDC inside the bilayers creates a "transient site", which is related to the anesthetic potency since it could modulate the access of these molecules to their binding site(s) in the voltage-gated sodium channel.

Energetics and dynamics of the fragmentation reactions of protonated peptides containing methionine sulfoxide or aspartic acid via energy- and time-resolved surface induced dissociation.

PubMed

Lioe, Hadi; Laskin, Julia; Reid, Gavin E; O'Hair, Richard A J

2007-10-25

The surface-induced dissociation (SID) of six model peptides containing either methionine sulfoxide or aspartic acid (GAILM(O)GAILR, GAILM(O)GAILK, GAILM(O)GAILA, GAILDGAILR, GAILDGAILK, and GAILDGAILA) have been studied using a specially configured Fourier transform ion-cyclotron resonance mass spectrometer (FT-ICR MS). In particular, we have investigated the energetics and dynamics associated with (i) preferential cleavage of the methionine sulfoxide side chain via the loss of CH3SOH (64 Da), and (ii) preferential cleavage of the amide bond C-terminal to aspartic acid. The role of proton mobility in these selective bond cleavage reactions was examined by changing the C-terminal residue of the peptide from arginine (nonmobile proton conditions) to lysine (partially mobile proton conditions) to alanine (mobile proton conditions). Time- and energy-resolved fragmentation efficiency curves (TFECs) reveal that selective cleavages due to the methionine sulfoxide and aspartic acid residues are characterized by slow fragmentation kinetics. RRKM modeling of the experimental data suggests that the slow kinetics is associated with large negative entropy effects and these may be due to the presence of rearrangements prior to fragmentation. It was found that the Arrhenius pre-exponential factor (A) for peptide fragmentations occurring via selective bond cleavages are 1-2 orders of magnitude lower than nonselective peptide fragmentation reactions, while the dissociation threshold (E0) is relatively invariant. This means that selective bond cleavage is kinetically disfavored compared to nonselective amide bond cleavage. It was also found that the energetics and dynamics for the preferential loss of CH3SOH from peptide ions containing methionine sulfoxide are very similar to selective C-terminal amide bond cleavage at the aspartic acid residue. These results suggest that while preferential cleavage can compete with amide bond cleavage energetically, dynamically, these processes are much slower compared to amide bond cleavage, explaining why these selective bond cleavages are not observed if fragmentation is performed under mobile proton conditions. This study further affirms that fragmentation of peptide ions in the gas phase are predominantly governed by entropic effects.

Dynamics of small flexible fibers in turbulent channel flow

NASA Astrophysics Data System (ADS)

Marchioli, Cristian; Dotto, Diego; Soldati, Alfredo

2017-11-01

In this paper we investigate the dynamics of small flexible fibers in turbulent channel flow. Our aim is to examine the effect of local shear and turbulence anisotropy on the translation and rotation of fibers with different elongation and inertia. To these aims, we use a Eulerian-Lagrangian approach based on direct numerical simulation of turbulence in the dilute regime, and we model fibers, which are longer than the Kolmogorov scale, as chains of sub-Kolmogorov rods connected through ball-and-socket joints that enable bending and twisting. Velocity, orientation and concentration statistics, extracted from simulations at Reτ = 300 , are presented to give insights into the complex fibers-turbulence interactions that arise when non-sphericity and deformability add to inertial bias. Compared to fibers that translate and rotate as rigid bodies relative to the surrounding fluid, flexible fibers exhibit a stronger tendency to accumulate in the near-wall region, where they are trapped by the same mechanisms that govern preferential concentration of spherical particles. In such region, the mean shear is strong enough to reduce bending and stretch the fibers. Preferential segregation into low-speed streaks and preferential orientation in the mean flow direction are also observed.

A Hybrid Analytical/Numerical Model for the Characterization of Preferential Flow Path with Non-Darcy Flow

PubMed Central

Wang, Sen; Feng, Qihong; Han, Xiaodong

2013-01-01

Due to the long-term fluid-solid interactions in waterflooding, the tremendous variation of oil reservoir formation parameters will lead to the widespread evolution of preferential flow paths, thereby preventing the further enhancement of recovery efficiency because of unstable fingering and premature breakthrough. To improve oil recovery, the characterization of preferential flow paths is essential and imperative. In efforts that have been previously documented, fluid flow characteristics within preferential paths are assumed to obey Darcy's equation. However, the occurrence of non-Darcy flow behavior has been increasingly suggested. To examine this conjecture, the Forchheimer number with the inertial coefficient estimated from different empirical formulas is applied as the criterion. Considering a 10% non-Darcy effect, the fluid flow in a preferential path may do experience non-Darcy behavior. With the objective of characterizing the preferential path with non-Darcy flow, a hybrid analytical/numerical model has been developed to investigate the pressure transient response, which dynamically couples a numerical model describing the non-Darcy effect of a preferential flow path with an analytical reservoir model. The characteristics of the pressure transient behavior and the sensitivities of corresponding parameters have also been discussed. In addition, an interpretation approach for pressure transient testing is also proposed, in which the Gravitational Search Algorithm is employed as a non-linear regression technology to match measured pressure with this hybrid model. Examples of applications from different oilfields are also presented to illustrate this method. This cost-effective approach provides more accurate characterization of a preferential flow path with non-Darcy flow, which will lay a solid foundation for the design and operation of conformance control treatments, as well as several other Enhanced Oil Recovery projects. PMID:24386224

Tests of Theories of Crime in Female Prisoners.

PubMed

Lindberg, Marc A; Fugett, April; Adkins, Ashtin; Cook, Kelsey

2017-02-01

Several general theories of crime were tested with path models on 293 female prisoners in a U.S. State prison. The theories tested included Social Bond and Control, Thrill/Risk Seeking, and a new attachment-based Developmental Dynamic Systems model. A large battery of different instruments ranging from measures of risk taking, to a crime addiction scale, to Childhood Adverse Events, to attachments and clinical issues were used. The older general theories of crime did not hold up well under the rigor of path modeling. The new dynamic systems model was supported that incorporated adverse childhood events leading to (a) peer crime, (b) crime addiction, and (c) a measure derived from the Attachment and Clinical Issues Questionnaire (ACIQ) that takes individual differences in attachments and clinical issues into account. The results were discussed in terms of new approaches to Research Defined Criteria of Diagnosis (RDoC) and new approaches to intervention.

An attachment model of depression: integrating findings from the mood disorder laboratory.

PubMed

Holmes, Jeremy

2013-01-01

This paper is written from a psychodynamic clinician's perspective, juxtaposing a psychoanalytic-attachment model of depression with recent developments in neuroscience. Three main components of the attachment approach are described: the role of loss, of childhood trauma predisposing to depression in later life, and failure of co-regulation of role of primitive emotions, such as fear, despair, and helplessness. Blatt's distinction between anaclitic and introjective depression is delineated and related to hyper- and de-activation of the attachment dynamic. Recent advances in evolutionary, sociological, epigenetic, biochemical, and neuro-imaging studies of depression are reviewed. A dynamic model of depression is proposed, linking interpersonal and intra-psychic perspectives with neuro-anatomical models. The final section of the paper considers the specific role of psychodynamic approaches to the treatment of refractory depression. These include length of treatment, capacity to rework implicit memories, and focus on transference and counter-transference.

Simultaneous dynamic optical and electrical properties of endothelial cell attachment on indium tin oxide bioelectrodes.

PubMed

Choi, Chang K; English, Anthony E; Kihm, Kenneth D; Margraves, Charles H

2007-01-01

This study quantifies the dynamic attachment and spreading of porcine pulmonary artery endothelial cells (PPAECs) on optically thin, indium tin oxide (ITO) biosensors using simultaneous differential interference contrast microscopy (DICM) and electrical microimpedance spectroscopy. A lock-in amplifier circuit monitored the impedance of PPAECs cultivated on the transparent ITO bioelectrodes as a function of frequency between 10 Hz and 100 kHz and as a function of time, while DICM images were simultaneously acquired. A digital image processing algorithm quantified the cell-covered electrode area as a function of time. The results of this study show that the fraction of the cell-covered electrode area is in qualitative agreement with the electrical impedance during the attachment phase following the cell settling on the electrode surface. The possibility of several distinctly different states of electrode coverage and cellular attachment giving rise to similar impedance signals is discussed.

Infant bonding and attachment to the caregiver: insights from basic and clinical science.

PubMed

Sullivan, Regina; Perry, Rosemarie; Sloan, Aliza; Kleinhaus, Karine; Burtchen, Nina

2011-12-01

Early life infant-caregiver attachment is a dynamic, bidirectional process that involving both the infant and caregiver. Infant attachment appears to have a dual function. First, it ensures the infant remains close to the caregiver in order to receive necessary care for survival. Second, the quality of attachment and its associated sensory stimuli organize the brain to define the infant's cognitive and emotional development. Here we present attachment within an historical view and highlight the importance of integrating human and animal research in understanding infant care. Copyright © 2011 Elsevier Inc. All rights reserved.

Distorted asymmetric cubic nanostructure of soluble fullerene crystals in efficient polymer:fullerene solar cells.

PubMed

Kim, Youngkyoo; Nelson, Jenny; Zhang, Tong; Cook, Steffan; Durrant, James R; Kim, Hwajeong; Park, Jiho; Shin, Minjung; Nam, Sungho; Heeney, Martin; McCulloch, Iain; Ha, Chang-Sik; Bradley, Donal D C

2009-09-22

We found that 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C(61) (PCBM) molecules make a distorted asymmetric body-centered cubic crystal nanostructure in the bulk heterojunction films of reigoregular poly(3-hexylthiophene) and PCBM. The wider angle of distortion in the PCBM nanocrystals was approximately 96 degrees , which can be assigned to the influence of the attached side group to the fullerene ball of PCBM to bestow solubility. Atom concentration analysis showed that after thermal annealing the PCBM nanocrystals do preferentially distribute above the layer of P3HT nanocrystals inside devices.

The investigation of social networks based on multi-component random graphs

NASA Astrophysics Data System (ADS)

Zadorozhnyi, V. N.; Yudin, E. B.

2018-01-01

The methods of non-homogeneous random graphs calibration are developed for social networks simulation. The graphs are calibrated by the degree distributions of the vertices and the edges. The mathematical foundation of the methods is formed by the theory of random graphs with the nonlinear preferential attachment rule and the theory of Erdôs-Rényi random graphs. In fact, well-calibrated network graph models and computer experiments with these models would help developers (owners) of the networks to predict their development correctly and to choose effective strategies for controlling network projects.

Percolation and epidemics in random clustered networks

NASA Astrophysics Data System (ADS)

Miller, Joel C.

2009-08-01

The social networks that infectious diseases spread along are typically clustered. Because of the close relation between percolation and epidemic spread, the behavior of percolation in such networks gives insight into infectious disease dynamics. A number of authors have studied percolation or epidemics in clustered networks, but the networks often contain preferential contacts in high degree nodes. We introduce a class of random clustered networks and a class of random unclustered networks with the same preferential mixing. Percolation in the clustered networks reduces the component sizes and increases the epidemic threshold compared to the unclustered networks.

Dynamic self-cleaning in gecko setae via digital hyperextension

PubMed Central

Hu, Shihao; Lopez, Stephanie; Niewiarowski, Peter H.; Xia, Zhenhai

2012-01-01

Gecko toe pads show strong adhesion on various surfaces yet remain remarkably clean around everyday contaminants. An understanding of how geckos clean their toe pads while being in motion is essential for the elucidation of animal behaviours as well as the design of biomimetic devices with optimal performance. Here, we test the self-cleaning of geckos during locomotion. We provide, to our knowledge, the first evidence that geckos clean their feet through a unique dynamic self-cleaning mechanism via digital hyperextension. When walking naturally with hyperextension, geckos shed dirt from their toes twice as fast as they would if walking without hyperextension, returning their feet to nearly 80 per cent of their original stickiness in only four steps. Our dynamic model predicts that when setae suddenly release from the attached substrate, they generate enough inertial force to dislodge dirt particles from the attached spatulae. The predicted cleaning force on dirt particles significantly increases when the dynamic effect is included. The extraordinary design of gecko toe pads perfectly combines dynamic self-cleaning with repeated attachment/detachment, making gecko feet sticky yet clean. This work thus provides a new mechanism to be considered for biomimetic design of highly reuseable and reliable dry adhesives and devices. PMID:22696482

Subsurface lateral preferential flow network revealed by time-lapse ground-penetrating radar in a hillslope

NASA Astrophysics Data System (ADS)

Guo, Li; Chen, Jin; Lin, Henry

2014-12-01

Subsurface lateral preferential flow (LPF) has been observed to contribute substantially to hillslope and catchment runoff. However, the complex nature of LPF and the lack of an appropriate investigation method have hindered direct LPF observation in the field. Thus, the initiation, persistence, and dynamics of LPF networks remain poorly understood. This study explored the application of time-lapse ground-penetrating radar (GPR) together with an artificial infiltration to shed light on the nature of LPF and its dynamics in a hillslope. Based on our enhanced field experimental setup and carefully refined GPR data postprocessing algorithms, we developed a new protocol to reconstruct LPF networks with centimeter resolution. This is the first time that a detailed LPF network and its dynamics have been revealed noninvasively along a hillslope. Real-time soil water monitoring and field soil investigation confirmed the locations of LPF mapped by time-lapse GPR surveys. Our results indicated the following: (1) Increased spatial variations of radar signals after infiltration suggested heterogeneous soil water changes within the studied soil, which reflected the generation and dynamics of LPF; (2) Two types of LPF networks were identified, the network at the location of soil permeability contrasts and that formed via a series of connected preferential flow paths; and (3) The formation and distribution of LPF networks were influenced by antecedent soil water condition. Overall, this study demonstrates clearly that carefully designed time-lapse GPR surveys with enhanced data postprocessing offer a practical and nondestructive way of mapping LPF networks in the field, thereby providing a potentially significant enhancement in our ability to study complex subsurface flow processes across the landscape.

Dynamics of HIV-1 Assembly and Release

PubMed Central

Ivanchenko, Sergey; Godinez, William J.; Lampe, Marko; Kräusslich, Hans-Georg; Eils, Roland; Rohr, Karl; Bräuchle, Christoph; Müller, Barbara; Lamb, Don C.

2009-01-01

Assembly and release of human immunodeficiency virus (HIV) occur at the plasma membrane of infected cells and are driven by the Gag polyprotein. Previous studies analyzed viral morphogenesis using biochemical methods and static images, while dynamic and kinetic information has been lacking until very recently. Using a combination of wide-field and total internal reflection fluorescence microscopy, we have investigated the assembly and release of fluorescently labeled HIV-1 at the plasma membrane of living cells with high time resolution. Gag assembled into discrete clusters corresponding to single virions. Formation of multiple particles from the same site was rarely observed. Using a photoconvertible fluorescent protein fused to Gag, we determined that assembly was nucleated preferentially by Gag molecules that had recently attached to the plasma membrane or arrived directly from the cytosol. Both membrane-bound and cytosol derived Gag polyproteins contributed to the growing bud. After their initial appearance, assembly sites accumulated at the plasma membrane of individual cells over 1–2 hours. Assembly kinetics were rapid: the number of Gag molecules at a budding site increased, following a saturating exponential with a rate constant of ∼5×10−3 s−1, corresponding to 8–9 min for 90% completion of assembly for a single virion. Release of extracellular particles was observed at ∼1,500±700 s after the onset of assembly. The ability of the virus to recruit components of the cellular ESCRT machinery or to undergo proteolytic maturation, or the absence of Vpu did not significantly alter the assembly kinetics. PMID:19893629

Measuring discursive influence across scholarship.

PubMed

Gerow, Aaron; Hu, Yuening; Boyd-Graber, Jordan; Blei, David M; Evans, James A

2018-03-27

Assessing scholarly influence is critical for understanding the collective system of scholarship and the history of academic inquiry. Influence is multifaceted, and citations reveal only part of it. Citation counts exhibit preferential attachment and follow a rigid "news cycle" that can miss sustained and indirect forms of influence. Building on dynamic topic models that track distributional shifts in discourse over time, we introduce a variant that incorporates features, such as authorship, affiliation, and publication venue, to assess how these contexts interact with content to shape future scholarship. We perform in-depth analyses on collections of physics research (500,000 abstracts; 102 years) and scholarship generally (JSTOR repository: 2 million full-text articles; 130 years). Our measure of document influence helps predict citations and shows how outcomes, such as winning a Nobel Prize or affiliation with a highly ranked institution, boost influence. Analysis of citations alongside discursive influence reveals that citations tend to credit authors who persist in their fields over time and discount credit for works that are influential over many topics or are "ahead of their time." In this way, our measures provide a way to acknowledge diverse contributions that take longer and travel farther to achieve scholarly appreciation, enabling us to correct citation biases and enhance sensitivity to the full spectrum of scholarly impact. Copyright © 2018 the Author(s). Published by PNAS.

Measuring discursive influence across scholarship

PubMed Central

Gerow, Aaron; Hu, Yuening; Boyd-Graber, Jordan; Blei, David M.

2018-01-01

Assessing scholarly influence is critical for understanding the collective system of scholarship and the history of academic inquiry. Influence is multifaceted, and citations reveal only part of it. Citation counts exhibit preferential attachment and follow a rigid “news cycle” that can miss sustained and indirect forms of influence. Building on dynamic topic models that track distributional shifts in discourse over time, we introduce a variant that incorporates features, such as authorship, affiliation, and publication venue, to assess how these contexts interact with content to shape future scholarship. We perform in-depth analyses on collections of physics research (500,000 abstracts; 102 years) and scholarship generally (JSTOR repository: 2 million full-text articles; 130 years). Our measure of document influence helps predict citations and shows how outcomes, such as winning a Nobel Prize or affiliation with a highly ranked institution, boost influence. Analysis of citations alongside discursive influence reveals that citations tend to credit authors who persist in their fields over time and discount credit for works that are influential over many topics or are “ahead of their time.” In this way, our measures provide a way to acknowledge diverse contributions that take longer and travel farther to achieve scholarly appreciation, enabling us to correct citation biases and enhance sensitivity to the full spectrum of scholarly impact. PMID:29531061

Actin filament curvature biases branching direction

NASA Astrophysics Data System (ADS)

Wang, Evan; Risca, Viviana; Chaudhuri, Ovijit; Chia, Jia-Jun; Geissler, Phillip; Fletcher, Daniel

2012-02-01

Actin filaments are key components of the cellular machinery, vital for a wide range of processes ranging from cell motility to endocytosis. Actin filaments can branch, and essential in this process is a protein complex known as the Arp2/3 complex, which nucleate new ``daughter'' filaments from pre-existing ``mother'' filaments by attaching itself to the mother filament. Though much progress has been made in understanding the Arp2/3-actin junction, some very interesting questions remain. In particular, F-actin is a dynamic polymer that undergoes a wide range of fluctuations. Prior studies of the Arp2/3-actin junction provides a very static notion of Arp2/3 binding. The question we ask is how differently does the Arp2/3 complex interact with a straight filament compared to a bent filament? In this study, we used Monte Carlo simulations of a surface-tethered worm-like chain to explore possible mechanisms underlying the experimental observation that there exists preferential branch formation by the Arp2/3 complex on the convex face of a curved filament. We show that a fluctuation gating model in which Arp2/3 binding to the actin filament is dependent upon a rare high-local-curvature shape fluctuation of the filament is consistent with the experimental data.

Tests of the Attachment and Developmental Dynamic Systems Theory of Crime (ADDSTOC): Toward a Differential RDoC Diagnostic and Treatment Approach.

PubMed

Lindberg, Marc A; Zeid, Dana

2018-01-01

The Attachment and Developmental Dynamic Systems Theory of Crime was tested on 206 male inmates. They completed measures tapping attachments, clinical issues, adverse childhood events, peer crime, and crime addictions. A significant path model was found, going from insecure parental attachments to adverse childhood events, and then on to the behavioral crime addiction and criminal peers scales. Peer crime was also predicted by insecure parent attachments and the crime addiction scale. Finally, the crime addiction, peer crime, and insecure parental attachment scales predicted frequencies of criminal behavior. The model also fit a sample of 239 female inmates. The notions of crime addiction, in this context of adverse events and insecure parental attachments, offered newer and more powerful explanations than previously offered by social learning theories on why some individuals are more likely to associate with peers engaging in criminal behavior, and also how these combine to predict degrees of criminal behavior. By moving beyond main effects models, it was found that a focus on systems of interactions was robust in theory and application. However, profile data from the Attachment and Clinical Issues Questionnaire showed that individual differences in Research Domain Criteria diagnoses are fundamental to treatment settings. Such approaches to reducing rates of recidivism and substance abuse should also enhance outcomes in many domains, including HIV prevention, costs to health care, and at the same time increase overall public safety.

Ion-momentum imaging of dissociative attachment of electrons to molecules

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

Slaughter, D. S.; Belkacem, A.; McCurdy, C. W.

Here, we present an overview of experiments and theory relevant to dissociative electron attachment studied by momentum imaging. We describe several key examples of characteristic transient anion dynamics in the form of small polyatomic electron-molecule systems. In each of these examples the so-called axial recoil approximation is found to break down due to correlation of the electronic and nuclear degrees of freedom of the transient anion. Guided by anion fragment momentum measurements and predictions of the electron scattering attachment probability in the molecular frame, we demonstrate that accurate predictions of the dissociation dynamics can be achieved without a detailed investigationmore » of the surface topology of the relevant electronic states or the fragment trajectories on those surfaces.« less

Ion-momentum imaging of dissociative attachment of electrons to molecules

DOE PAGES

Slaughter, D. S.; Belkacem, A.; McCurdy, C. W.; ...

2016-10-24

Here, we present an overview of experiments and theory relevant to dissociative electron attachment studied by momentum imaging. We describe several key examples of characteristic transient anion dynamics in the form of small polyatomic electron-molecule systems. In each of these examples the so-called axial recoil approximation is found to break down due to correlation of the electronic and nuclear degrees of freedom of the transient anion. Guided by anion fragment momentum measurements and predictions of the electron scattering attachment probability in the molecular frame, we demonstrate that accurate predictions of the dissociation dynamics can be achieved without a detailed investigationmore » of the surface topology of the relevant electronic states or the fragment trajectories on those surfaces.« less

Contributions of microtubule rotation and dynamic instability to kinetochore capture

NASA Astrophysics Data System (ADS)

Sweezy-Schindler, Oliver; Edelmaier, Christopher; Blackwell, Robert; Glaser, Matt; Betterton, Meredith

2014-03-01

The capture of lost kinetochores (KCs) by microtubules (MTs) is a crucial part of prometaphase during mitosis. Microtubule dynamic instability has been considered the primary mechanism of KC capture, but recent work discovered that lateral KC attachment to pivoting MTs enabled rapid capture even with significantly reduced MT dynamics. We aim to understand the relative contributions of MT rotational diffusion and dynamic instability to KC capture, as well as KC capture through end-on and/or lateral attachment. Our model consists of rigid MTs and a spherical KC, which are allowed to diffuse inside a spherical nuclear envelope consistent with the geometry of fission yeast. For simplicity, we include a single spindle pole body, which is anchored to the nuclear membrane, and its associated polar MTs. Brownian dynamics treats the diffusion of the MTs and KC and kinetic Monte Carlo models stochastic processes such as dynamic instability. NSF 1546021.

Molecular Packing of High-Mobility Diketo Pyrrolo-Pyrrole Polymer Semiconductors with Branched Alkyl Side Chains

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

X Zhang; L Richter; D DeLongchamp

We describe a series of highly soluble diketo pyrrolo-pyrrole (DPP)-bithiophene copolymers exhibiting field effect hole mobilities up to 0.74 cm{sup 2} V{sup -1} s{sup -1}, with a common synthetic motif of bulky 2-octyldodecyl side groups on the conjugated backbone. Spectroscopy, diffraction, and microscopy measurements reveal a transition in molecular packing behavior from a preferentially edge-on orientation of the conjugated plane to a preferentially face-on orientation as the attachment density of the side chains increases. Thermal annealing generally reduces both the face-on population and the misoriented edge-on domains. The highest hole mobilities of this series were obtained from edge-on molecular packingmore » and in-plane liquid-crystalline texture, but films with a bimodal orientation distribution and no discernible in-plane texture exhibited surprisingly comparable mobilities. The high hole mobility may therefore arise from the molecular packing feature common to the entire polymer series: backbones that are strictly oriented parallel to the substrate plane and coplanar with other backbones in the same layer.« less

Specific end-to-end attachment of chromosomes in Ornithogalum virens.

PubMed

Ashley, T

1979-08-01

C-banding of nonhomologous chromosomes in haploid generative nuclei of Ornithogalum virens (n = 3) reveals a high degree of specificity with respect to end-to-end connexions. The centromeric end of chromosome 2 preferentially associates with the centromeric end of chromosome 3 and the telomeric end of chromosome 3 associates preferentially with the telomeric end of chromosome 1. This same association of nonhomologous chromosomes persists in prophase nuclei of diploid root tips. In addition, the telomeric ends of the 2 chromosome 2s are connected to one another as are the centromeric ends of the chromosome 1s. This results in a ring of chromosomes in which homologues lie opposite one another. Centromeric ends lie on one side of the nucleus and telomeric ends on the other. It is proposed that this specific association of chromosome ends reflects an order which was probably established at the preceding anaphase or telophase and which persists throughout interphase. The suggestion is made that the proximity of homologous ends and consequently homologous alignment may facilitate initiation of pairing at meiosis.

Interdependence of attachment styles and relationship quality in parent-adolescent dyads.

PubMed

Chow, Chong Man; Hart, Ellen; Ellis, Lillian; Tan, Cin Cin

2017-12-01

The current study examined how attachment styles of parents and adolescents may jointly influence the quality of their relationship. Parent-adolescent (N dyads  = 77) pairs were recruited from a Midwestern town in the United States. The mean of adolescents' age was 16.25. Both members reported their attachment styles, relationship closeness, and relationship discord. The Actor-Partner Interdependence Model (APIM) showed that both members' attachment avoidance was associated with self-report lower levels of closeness. Parents' attachment anxiety was related to relationship discord. Parents with higher avoidant attachment reported lower closeness when adolescents were higher in avoidant attachment. Higher parents' anxious attachment was related to higher relationship closeness when adolescents were higher on anxious attachment. Such an association was negative when adolescents had lower anxious attachment. Higher parents' anxious attachment was related to greater discord when adolescents were lower on anxiety attachment. This study reveals the complex dyadic dynamics of relationship quality in parent-adolescent pairs. Copyright © 2017 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

Rapid runoff via shallow throughflow and deeper preferential flow in a boreal catchment underlain by frozen silt (Alaska, USA)

USGS Publications Warehouse

Koch, Joshua C.; Ewing, Stephanie A.; Striegl, Robert G.; McKnight, Diane M.

2013-01-01

In high-latitude catchments where permafrost is present, runoff dynamics are complicated by seasonal active-layer thaw, which may cause a change in the dominant flowpaths as water increasingly contacts mineral soils of low hydraulic conductivity. A 2-year study, conducted in an upland catchment in Alaska (USA) underlain by frozen, well-sorted eolian silt, examined changes in infiltration and runoff with thaw. It was hypothesized that rapid runoff would be maintained by flow through shallow soils during the early summer and deeper preferential flow later in the summer. Seasonal changes in soil moisture, infiltration, and runoff magnitude, location, and chemistry suggest that transport is rapid, even when soils are thawed to their maximum extent. Between June and September, a shift occurred in the location of runoff, consistent with subsurface preferential flow in steep and wet areas. Uranium isotopes suggest that late summer runoff erodes permafrost, indicating that substantial rapid flow may occur along the frozen boundary. Together, throughflow and deep preferential flow may limit upland boreal catchment water and solute storage, and subsequently biogeochemical cycling on seasonal to annual timescales. Deep preferential flow may be important for stream incision, network drainage development, and the release of ancient carbon to ecosystems

Stability of Attachment Style in Adolescence: An Empirical Test of Alternative Developmental Processes.

PubMed

Jones, Jason D; Fraley, R Chris; Ehrlich, Katherine B; Stern, Jessica A; Lejuez, C W; Shaver, Phillip R; Cassidy, Jude

2018-05-01

Few studies have examined stability and change in attachment during adolescence. This 5-year longitudinal study (a) examined whether prototype or revisionist developmental dynamics better characterized patterns of stability and change in adolescent attachment (at T1, N = 176; M age  = 14.0 years, SD = 0.9), (b) tested potential moderators of prototype-like attachment stability, and (c) compared attachment stability in adolescence to stability in adulthood. The results supported the prototype model, which assumes that there is a stable, enduring factor underlying stability and change in attachment. Exploratory moderation analyses revealed that family conflict, parental separation or divorce, minority status, and male sex might undermine the prototype-like stability of adolescent attachment. Stability of attachment was lower in adolescence relative to adulthood. © 2017 The Authors. Child Development © 2017 Society for Research in Child Development, Inc.

Attachment Theory: Implications for School Psychology

ERIC Educational Resources Information Center

Kennedy, Janice H.; Kennedy, Charles E.

2004-01-01

The effective practice of school psychology requires a strong research and theoretical base, a framework that encompasses developmental processes and outcomes, both adaptive and maladaptive, which facilitates assessment and intervention and offers insight into classroom and family dynamics. Attachment theory provides the school psychologist with…

Network evolution by nonlinear preferential rewiring of edges

NASA Astrophysics Data System (ADS)

Xu, Xin-Jian; Hu, Xiao-Ming; Zhang, Li-Jie

2011-06-01

The mathematical framework for small-world networks proposed in a seminal paper by Watts and Strogatz sparked a widespread interest in modeling complex networks in the past decade. However, most of research contributing to static models is in contrast to real-world dynamic networks, such as social and biological networks, which are characterized by rearrangements of connections among agents. In this paper, we study dynamic networks evolved by nonlinear preferential rewiring of edges. The total numbers of vertices and edges of the network are conserved, but edges are continuously rewired according to the nonlinear preference. Assuming power-law kernels with exponents α and β, the network structures in stationary states display a distinct behavior, depending only on β. For β>1, the network is highly heterogeneous with the emergence of starlike structures. For β<1, the network is widely homogeneous with a typical connectivity. At β=1, the network is scale free with an exponential cutoff.

Evaluation of the effects of one year's operation of the dynamic preferential runway system. [human reactions to overflight air traffic pattern

NASA Technical Reports Server (NTRS)

Borsky, P. N.

1974-01-01

The FAA introduced an experimental aircraft operations program at JFK Airport called the Dynamic Preferential Runway System (DPRS) in the summer of 1971. The program is designed to distribute air traffic as equally as possible over the surrounding communities, to limit periods of continuous overflight and to vary the same hours of overflight from day to day. After a full year's operation, an evaluation was made of the system's effectiveness. All of the operation's goals were moderately achieved with the greatest relief in reduced overflight afforded the most heavily impacted areas. Few residents, however, were aware of DPRS or felt that it had greatly reduced annoyance or represented a major effort by the aircraft authorities. Statistical analyses of reported annoyance obtained from two independent surveys in 1969 and 1972 reveal limited reductions in annoyance in 1972, with shifts from reported high annoyance to moderate annoyance.

Intelligent Robotic Systems Study (IRSS), phase 3

NASA Technical Reports Server (NTRS)

1991-01-01

This phase of the Intelligent Robotic Systems Study (IRSS) examines some basic dynamics and control issues for a space manipulator attached to its worksite through a compliant base. One example of this scenario is depicted, which is a simplified, planar representation of the Flight Telerobotic Servicer (FTS) Development Test Flight 2 (DTF-2) experiment. The system consists of 4 major components: (1) dual FTS arms to perform dextrous tasks; (2) the main body to house power and electronics; (3) an Attachment Stabilization and Positioning Subsystem (ASPS) to provide coarse positioning and stabilization of the arms, and (4) the Worksite Attachment Mechanism (WAM) which anchors the system to its worksite, such as a Space Station truss node or Shuttle bay platform. The analysis is limited to the DTF-2 scenario. The goal is to understand the basic interaction dynamics between the arm, the positioner and/or stabilizer, and the worksite. The dynamics and controls simulation model are described. Analysis and simulation results are presented.

Social climber attachment in forming networks produces a phase transition in a measure of connectivity

NASA Astrophysics Data System (ADS)

Taylor, Dane; Larremore, Daniel B.

2012-09-01

The formation and fragmentation of networks are typically studied using percolation theory, but most previous research has been restricted to studying a phase transition in cluster size, examining the emergence of a giant component. This approach does not study the effects of evolving network structure on dynamics that occur at the nodes, such as the synchronization of oscillators and the spread of information, epidemics, and neuronal excitations. We introduce and analyze an alternative link-formation rule, called social climber (SC) attachment, that may be combined with arbitrary percolation models to produce a phase transition using the largest eigenvalue of the network adjacency matrix as the order parameter. This eigenvalue is significant in the analyses of many network-coupled dynamical systems in which it measures the quality of global coupling and is hence a natural measure of connectivity. We highlight the important self-organized properties of SC attachment and discuss implications for controlling dynamics on networks.

The Attachment and Clinical Issues Questionnaire: a new methodology for science and practice in criminology and forensics.

PubMed

Lindberg, Marc A; Fugett, April; Lounder, Lindsay

2014-10-01

Most modern theories suggest that interpersonal relationships are of central importance in the development of criminal behavior. We tested the parent attachment scales of a new research and clinical measure, the Attachment and Clinical Issues Questionnaire (ACIQ). It is a 29-scale battery assessing attachments to mother, father, partner, and peers, which also includes several related clinical scales. Sixty-one (18-20 years of age) male offenders from a maximum security detention center and 131 contrasts completed the ACIQ. ANOVA demonstrated that mother and father attachments displayed different patterns. The attachment scales also predicted the numbers of crimes within the population of juvenile offenders. Thus, the parent attachment scales of the ACIQ showed promise as an instrument to test dynamic systems approaches to developmental models of criminal behavior. © The Author(s) 2013.

Structural ordering at solid-liquid interfaces in Al-Sm system: A molecular-dynamics study

DOE PAGES

Sun, Yang; Zhang, Feng; Ye, Zhuo; ...

2016-07-12

The structural ordering at solid-liquid interfaces far from equilibrium is studied with molecular dynamics simulations for the Al-Sm system. Using the van-Hove self-correlation function as the criterion to identify attachment/detachment events that occur at the interface, we are able to determine the time-dependent interface position, and characterize the detailed interfacial structure ordering surrounding the attached atoms. For the interface between an undercooled Al90Sm10 liquid and a metastable cubic structure, the solid induces the crystalline order of the cubic phase in the liquid layers, promoting the continuous growth of the crystal phase. When the same liquid is put in contact withmore » f.c.c. Al, Sm from the liquid can still attach to the solid interface despite its insolubility in the Al lattice. Non-f.c.c. order is revealed surrounding the attached Sm atoms. Lastly, we show that the local structure ordering at interface is highly correlated to solid packing and liquid ordering.« less

The attachment system in fledgling relationships: an activating role for attachment anxiety.

PubMed

Eastwick, Paul W; Finkel, Eli J

2008-09-01

Is it sensible to study attachment dynamics between potential romantic partners before they share a full-fledged attachment bond? The present data indicate that such an approach may reveal novel insights about initial attraction processes. Four studies suggest that the state-like experience of attachment anxiety has functional implications within fledgling (i.e., desired or undeveloped) romantic relationships, well before the formation of an attachment bond. Studies 1 and 3 reveal that attachment anxiety directed toward a particular romantic interest is elevated before (in comparison with after) participants report being in an established relationship. Studies 2 and 3 demonstrate that such partner-specific attachment anxiety predicts attachment-relevant outcomes in fledgling relationships, including proximity seeking, safe haven, secure base, passionate love, and other approach behaviors. These associations were reliable above and beyond (and were typically as strong as or stronger than) the effect of sexual desire. Finally, Study 4 presents evidence that partner-specific attachment anxiety may cause several of these attachment-relevant outcomes. Attachment anxiety seems to be a normative experience and may signal the activation of the attachment system during the earliest stages of romantic relationships.

Factor VII and protein C are phosphatidic acid-binding proteins.

PubMed

Tavoosi, Narjes; Smith, Stephanie A; Davis-Harrison, Rebecca L; Morrissey, James H

2013-08-20

Seven proteins in the human blood clotting cascade bind, via their GLA (γ-carboxyglutamate-rich) domains, to membranes containing exposed phosphatidylserine (PS), although with membrane binding affinities that vary by 3 orders of magnitude. Here we employed nanodiscs of defined phospholipid composition to quantify the phospholipid binding specificities of these seven clotting proteins. All bound preferentially to nanobilayers in which PS headgroups contained l-serine versus d-serine. Surprisingly, however, nanobilayers containing phosphatidic acid (PA) bound substantially more of two of these proteins, factor VIIa and activated protein C, than did equivalent bilayers containing PS. Consistent with this finding, liposomes containing PA supported higher proteolytic activity by factor VIIa and activated protein C toward their natural substrates (factors X and Va, respectively) than did PS-containing liposomes. Moreover, treating activated human platelets with phospholipase D enhanced the rates of factor X activation by factor VIIa in the presence of soluble tissue factor. We hypothesize that factor VII and protein C bind preferentially to the monoester phosphate of PA because of its accessibility and higher negative charge compared with the diester phosphates of most other phospholipids. We further found that phosphatidylinositol 4-phosphate, which contains a monoester phosphate attached to its myo-inositol headgroup, also supported enhanced enzymatic activity of factor VIIa and activated protein C. We conclude that factor VII and protein C bind preferentially to monoester phosphates, which may have implications for the function of these proteases in vivo.

Space Shuttle Projects

NASA Image and Video Library

1978-09-01

Workmen in the Dynamic Test Stand lowered the nose cone into place to complete stacking of the left side of the solid rocket booster (SRB) in the Dynamic Test Stand at the east test area of the Marshall Space Flight Center (MSFC). The SRB would be attached to the external tank (ET) and then the orbiter later for the Mated Vertical Ground Vibration Test (MVGVT), that resumed in October 1978. The stacking of a complete Shuttle in the Dynamic Test Stand allowed test engineers to perform ground vibration testing on the Shuttle in its liftoff configuration. The purpose of the MVGVT was to verify that the Space Shuttle would perform as predicted during launch. The platforms inside the Dynamic Test Stand were modified to accommodate two SRB'S to which the ET was attached.

Comparing dynamic recording of infiltration by X-Ray tomography to the results of a dual porosity model for structured soils

NASA Astrophysics Data System (ADS)

Lissy, Anne-Sophie; Sammartino, Stephane; Di Pietro, Liliana; Lecompte, François; Ruy, Stephane

2017-04-01

With climate change, preferential flow phenomenon in soil could be predominant in Mediterranean zone. Understanding this phenomenon becomes a fundamental issue for preserving the water resource in quantity (drinking water) and quality (pesticide content). Non-invasive imaging technics, as X-ray tomography, allow studying water infiltration in laboratory with time-lapse imaging to visualize preferential flow path in soil columns (Sammartino et al. 2012). The modeling of water flow with a dual porosity model (matrix and macropores) integrates these fast flow phenomena (Ilhem 2014). These models, however needs more explicit links with the soil structure. The comparison of experimental results of infiltration (dynamics images and mass data) and modeling could improve our comprehension of preferential flow phenomenon and allow a better integration of the functional macroporosity (i.e. which drains water infiltration during a rain event) in such mass transfer models (Sammartino et al. 2015). Soil columns (Ø 12 cm - hauteur 13 cm, clay-loamy & medium sandy loam) have been sampled in the field to preserve their structure (field plowed or not). Several rains have been simulated in the laboratory and the last one was performed in an X-ray medical scanner (Siemens Somatom® 128 slices) at the CIRE platform (INRA, Centre - Val de Loire). Total and functional macro porosities were identified from time lapse tridimensional images. Water dynamics in the porosities was characterized from the identification and analysis of voxels filled by water. With an image resolution of 350μm only water in the largest macropores can be identified. The modeling of these experiments was carried out via the VirtualSoil platform (UMR Emmah, Avignon; www6.inra.fr/vsoil) using a water flow model coupling Darcy-Richards and KDW equations (Di Pietro et al., 2003). The simulated water flux drained by macropores is similar to the experimental hydrograph obtained for rainfalls on soils close to the saturation. The model reproduced well the flow dynamics: (1) breakthrough time (arrival time of the first drop at the bottom of the column) and (2) the total drained water quantity. A sensitivity analysis of this model is in progress in order to determine the influence of each KDW parameters (two kinematic parameters and one dispersion parameter) and to probe where the functional soil structure could be accounted for in the model structure or in the model parameters. First results show that the kinematic parameters modify the breakthrough time and the slope of the drainage curve. Keywords: functional macroporosity, modeling, RX tomography, infiltration, Richards and KDW equations. Sammartino et al., 2012. A novel method to visualize and characterize preferential flow in undisturbed soil cores by using multislice helical CT. Vadose Zone Journal. Sammartino et Lissy, 2015. Identifying the functional macropore network related to preferential flow in structured soils, Vadose Zone Journal, vol. 14, no. 10. Di Pietro et al. 2003. Predicting preferential water flow in soils by traveling-dispersive waves. Journal of Hydrology (278), pp.64-75. Adel Ilhem (2014) - Modélisation des transferts d'eau dans les sols hétérogènes (internship report)

Modeling the locomotion of the African trypanosome using multi-particle collision dynamics

NASA Astrophysics Data System (ADS)

Babu, Sujin B.; Stark, Holger

2012-08-01

The African trypanosome is a single flagellated micro-organism that causes the deadly sleeping sickness in humans and animals. We study the locomotion of a model trypanosome by modeling the spindle-shaped cell body using an elastic network of vertices with additional bending rigidity. The flagellum firmly attached to the model cell body is either straight or helical. A bending wave propagates along the flagellum and pushes the trypanosome forward in its viscous environment, which we simulate with the method of multi-particle collision dynamics. The relaxation dynamics of the model cell body due to a static bending wave reveals the sperm number from elastohydrodynamics as the relevant parameter. Characteristic cell body conformations for the helically attached flagellum resemble experimental observations. We show that the swimming velocity scales as the root of the angular frequency of the bending wave reminiscent of predictions for an actuated slender rod attached to a large viscous load. The swimming velocity for one geometry collapses on a single master curve when plotted versus the sperm number. The helically attached flagellum leads to a helical swimming path and a rotation of the model trypanosome about its long axis as observed in experiments. The simulated swimming velocity agrees with the experimental value.

"Not just a dog": an attachment perspective on relationships with assistance dogs.

PubMed

Kwong, Marilyn J; Bartholomew, Kim

2011-09-01

We explored individuals' relationships with an assistance dog from an attachment-theory perspective. We used both inductive and deductive thematic methods to analyze semi-structured interviews with 25 participants who had lost an assistance dog to retirement or death. Analyses revealed attachment processes of safe haven, secure base, and separation anxiety. Although attachment dynamics were an important feature of these relationships, caregiving was equally important. When confronted with the loss of their dog, almost all participants experienced intense grief. Most grief responses were consistent with the loss of a caregiving relationship. Findings suggest that grief is a natural response to the loss of a beloved companion who fulfilled fundamental needs for attachment and caregiving.

Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry

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

Wicklein, S.; Koehl, A.; Dittmann, R.

2012-09-24

By combining structural and chemical thin film analysis with detailed plume diagnostics and modeling of the laser plume dynamics, we are able to elucidate the different physical mechanisms determining the stoichiometry of the complex oxides model material SrTiO{sub 3} during pulsed laser deposition. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O{sub 2} background gas. On the one hand, a progressive preferential ablation of the Ti species with increasing laser fluence leads to a regime ofmore » Ti-rich thin film growth at larger fluences. On the other hand, in the low laser fluence regime, a more effective scattering of the lighter Ti plume species results in Sr rich films.« less

Dynamic formation of microenvironments at the myotendinous junction correlates with muscle fiber morphogenesis in zebrafish

PubMed Central

Snow, Chelsi J.; Henry, Clarissa A.

2009-01-01

Muscle development involves the specification and morphogenesis of muscle fibers that attach to tendons. After attachment, muscles and tendons then function as an integrated unit to transduce force to the skeletal system and stabilize joints. The attachment site is the myotendinous junction, or MTJ, and is the primary site of force transmission. We find that attachment of fast-twitch myofibers to the MTJ correlates with the formation of novel microenvironments within the MTJ. The expression or activation of two proteins involved in anchoring the intracellular cytoskeleton to the extracellular matrix, Focal adhesion kinase (Fak) and β-dystroglycan is up-regulated. Conversely, the extracellular matrix protein Fibronectin (Fn) is down-regulated. This degradation of Fn as fast-twitch fibers attach to the MTJ results in Fn protein defining a novel microenvironment within the MTJ adjacent to slow-twitch, but not fast-twitch, muscle. Interestingly, however, Fak, laminin, Fn and β-dystroglycan concentrate at the MTJ in mutants that do not have slow-twitch fibers. Taken together, these data elucidate novel and dynamic microenvironments within the MTJ and indicate that MTJ morphogenesis is spatially and temporally complex. PMID:18783736

Transient and chaotic low-energy transfers in a system with bistable nonlinearity

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

Romeo, F., E-mail: francesco.romeo@uniroma1.it; Manevitch, L. I.; Bergman, L. A.

2015-05-15

The low-energy dynamics of a two-dof system composed of a grounded linear oscillator coupled to a lightweight mass by means of a spring with both cubic nonlinear and negative linear components is investigated. The mechanisms leading to intense energy exchanges between the linear oscillator, excited by a low-energy impulse, and the nonlinear attachment are addressed. For lightly damped systems, it is shown that two main mechanisms arise: Aperiodic alternating in-well and cross-well oscillations of the nonlinear attachment, and secondary nonlinear beats occurring once the dynamics evolves solely in-well. The description of the former dissipative phenomenon is provided in a two-dimensionalmore » projection of the phase space, where transitions between in-well and cross-well oscillations are associated with sequences of crossings across a pseudo-separatrix. Whereas the second mechanism is described in terms of secondary limiting phase trajectories of the nonlinear attachment under certain resonance conditions. The analytical treatment of the two aformentioned low-energy transfer mechanisms relies on the reduction of the nonlinear dynamics and consequent analysis of the reduced dynamics by asymptotic techniques. Direct numerical simulations fully validate our analytical predictions.« less

Multicellular Self-Organization of P. aeruginosa due to Interactions with Secreted Trails.

PubMed

Gelimson, Anatolij; Zhao, Kun; Lee, Calvin K; Kranz, W Till; Wong, Gerard C L; Golestanian, Ramin

2016-10-21

Guided movement in response to slowly diffusing polymeric trails provides a unique mechanism for self-organization of some microorganisms. To elucidate how this signaling route leads to microcolony formation, we experimentally probe the trajectory and orientation of Pseudomonas aeruginosa that propel themselves on a surface using type IV pili motility appendages, which preferentially attach to deposited exopolysaccharides. We construct a stochastic model by analyzing single-bacterium trajectories and show that the resulting theoretical prediction for the many-body behavior of the bacteria is in quantitative agreement with our experimental characterization of how cells explore the surface via a power-law strategy.

Application of attachment modes in the control of large space structures

NASA Technical Reports Server (NTRS)

Craig, Roy R., Jr.

1989-01-01

Various ways are examined to obtain reduced order mathematical models of structures for use in dynamic response analyses and in controller design studies. Attachment modes are deflection shapes of a structure subjected to specified unit load distributions. Attachment modes are frequently employed to supplement free-interface normal modes to improve the modeling of components (structures) employed in component mode synthesis analyses. Deflection shapes of structures subjected to generalized loads of some specified distribution and of unit magnitude can also be considered to be attachment modes. Several papers which were written under this contract are summarized herein.

Phobias of attachment-related inner states in the psychotherapy of adult survivors of childhood complex trauma.

PubMed

Liotti, Giovanni

2013-11-01

The clinical case described in this article illustrates the value of taking into account the dynamics of disorganized attachment in the assessment of attachment-related phobias (phobia of attachment and phobia of attachment loss) during the psychotherapy of chronically traumatized patients. These seemingly opposite phobias typically coexist in the same patient, appear as phobias of both inner states (affect phobias) and relational experiences, and are linked to dissociated representations of self-with-other. Theory and research on attachment disorganization provide a clinician-friendly conceptual framework for capturing both the intrapsychic (e.g., intrusive and nonintegrated mental states) and the relational (e.g., dramatic unsolvable dilemmas in interpersonal exchanges) aspects of the attachment-related phobias. The therapeutic strategy and the key interventions that logically follow from a case formulation based on this conceptual framework are examined. © 2013 Wiley Periodicals, Inc.

Bioinspired, dynamic, structured surfaces for biofilm prevention

NASA Astrophysics Data System (ADS)

Epstein, Alexander K.

Bacteria primarily exist in robust, surface-associated communities known as biofilms, ubiquitous in both natural and anthropogenic environments. Mature biofilms resist a wide range of biocidal treatments and pose persistent pathogenic threats. Treatment of adherent biofilm is difficult, costly, and, in medical systems such as catheters, frequently impossible. Adding to the challenge, we have discovered that biofilm can be both impenetrable to vapors and extremely nonwetting, repelling even low surface tension commercial antimicrobials. Our study shows multiple contributing factors, including biochemical components and multiscale reentrant topography. Reliant on surface chemistry, conventional strategies for preventing biofilm only transiently affect attachment and/or are environmentally toxic. In this work, we look to Nature's antifouling solutions, such as the dynamic spiny skin of the echinoderm, and we develop a versatile surface nanofabrication platform. Our benchtop approach unites soft lithography, electrodeposition, mold deformation, and material selection to enable many degrees of freedom—material, geometric, mechanical, dynamic—that can be programmed starting from a single master structure. The mechanical properties of the bio-inspired nanostructures, verified by AFM, are precisely and rationally tunable. We examine how synthetic dynamic nanostructured surfaces control the attachment of pathogenic biofilms. The parameters governing long-range patterning of bacteria on high-aspect-ratio (HAR) nanoarrays are combinatorially elucidated, and we discover that sufficiently low effective stiffness of these HAR arrays mechanoselectively inhibits ˜40% of Pseudomonas aeruginosa biofilm attachment. Inspired by the active echinoderm skin, we design and fabricate externally actuated dynamic elastomer surfaces with active surface microtopography. We extract from a large parameter space the critical topographic length scales and actuation time scales for achieving nearly ˜80% attachment reduction. We furthermore investigate an atomically mobile, slippery liquid infused porous surface (SLIPS) inspired by the pitcher plant. We show up to 99.6% reduction of multiple pathogenic biofilms over a 7-day period under both static and physiologically realistic flow conditions—a ˜35x improvement over state-of-the-art surface chemistry, and over a far longer timeframe. Moreover, SLIPS is shown to be nontoxic: bacteria simply cannot attach to the smooth liquid interface. These bio-inspired strategies significantly advance biofilm attachment prevention and promise a tremendous range of industrial, clinical, and consumer applications.

Low-Speed Flight Dynamic Tests and Analysis of the Orion Crew Module Drogue Parachute System

NASA Technical Reports Server (NTRS)

Hahne, David E.; Fremaux, C. Michael

2008-01-01

A test of a dynamically scaled model of the NASA Orion Crew Module (CM) with drogue parachutes was conducted in the NASA-Langley 20-Foot Vertical Spin Tunnel. The primary test objective was to assess the ability of the Orion Crew Module drogue parachute system to adequately stabilize the CM and reduce angular rates at low subsonic Mach numbers. Two attachment locations were tested: the current design nominal and an alternate. Experimental results indicated that the alternate attachment location showed a somewhat greater tendency to attenuate initial roll rate and reduce roll rate oscillations than the nominal location. Comparison of the experimental data to a Program To Optimize Simulated Trajectories (POST II) simulation of the experiment yielded results for the nominal attachment point that indicate differences between the low-speed pitch and yaw damping derivatives in the aerodynamic database and the physical model. Comparisons for the alternate attachment location indicate that riser twist plays a significant role in determining roll rate attenuation characteristics. Reevaluating the impact of the alternate attachment points using a simulation modified to account for these results showed significantly reduced roll rate attenuation tendencies when compared to the original simulation. Based on this modified simulation the alternate attachment point does not appear to offer a significant increase in allowable roll rate over the nominal configuration.

Preferential solvation, ion pairing, and dynamics of concentrated aqueous solutions of divalent metal nitrate salts

NASA Astrophysics Data System (ADS)

Yadav, Sushma; Chandra, Amalendu

2017-12-01

We have investigated the characteristics of preferential solvation of ions, structure of solvation shells, ion pairing, and dynamics of aqueous solutions of divalent alkaline-earth metal nitrate salts at varying concentration by means of molecular dynamics simulations. Hydration shell structures and the extent of preferential solvation of the metal and nitrate ions in the solutions are investigated through calculations of radial distribution functions, tetrahedral ordering, and also spatial distribution functions. The Mg2+ ions are found to form solvent separated ion-pairs while the Ca2+ and Sr2+ ions form contact ion pairs with the nitrate ions. These findings are further corroborated by excess coordination numbers calculated through Kirkwood-Buff G factors for different ion-ion and ion-water pairs. The ion-pairing propensity is found to be in the order of Mg(NO3) 2 < C a (NO3) 2 < S r (NO3) 2, and it follows the trend given by experimental activity coefficients. It is found that proper modeling of these solutions requires the inclusion of electronic polarization of the ions which is achieved in the current study through electronic continuum correction force fields. A detailed analysis of the effects of ion-pairs on the structure and dynamics of water around the hydrated ions is done through classification of water into different subspecies based on their locations around the cations or anions only or bridged between them. We have looked at the diffusion coefficients, relaxation of orientational correlation functions, and also the residence times of different subspecies of water to explore the dynamics of water in different structural environments in the solutions. The current results show that the water molecules are incorporated into fairly well-structured hydration shells of the ions, thus decreasing the single-particle diffusivities and increasing the orientational relaxation times of water with an increase in salt concentration. The different structural motifs also lead to the presence of substantial dynamical heterogeneity in these solutions of strongly interacting ions. The current study helps us to understand the molecular details of hydration structure, ion pairing, and dynamics of water in the solvation shells and also of ion diffusion in aqueous solutions of divalent metal nitrate salts.

Attachment, self-esteem, worldviews, and terror management: evidence for a tripartite security system.

PubMed

Hart, Joshua; Shaver, Phillip R; Goldenberg, Jamie L

2005-06-01

On the basis of prior work integrating attachment theory and terror management theory, the authors propose a model of a tripartite security system consisting of dynamically interrelated attachment, self-esteem, and worldview processes. Four studies are presented that, combined with existing evidence, support the prediction derived from the model that threats to one component of the security system result in compensatory defensive activation of other components. Further, the authors predicted and found that individual differences in attachment style moderate the defenses. In Studies 1 and 2, attachment threats motivated worldview defense among anxiously attached participants and motivated self-enhancement (especially among avoidant participants), effects similar to those caused by mortality salience. In Studies 3 and 4, a worldview threat and a self-esteem threat caused attachment-related proximity seeking among fearful participants and avoidance of proximity among dismissing participants. The authors' model provides an overarching framework within which to study attachment, self-esteem, and worldviews.

The dynamics of attachment insecurity and paranoid thoughts: An experience sampling study.

PubMed

Sitko, Katarzyna; Varese, Filippo; Sellwood, William; Hammond, Amy; Bentall, Richard

2016-12-30

It has been proposed that insecure attachment can have adverse effects on the course of psychosis once symptoms have emerged. There is longitudinal evidence that increased insecure attachment is associated with increased severity of psychotic symptoms. The present study examined whether in the flow of daily life attachment insecurity fluctuates, whether elevated stress precedes the occurrence of attachment insecurity, and whether elevated attachment insecurity precedes the occurrence of paranoia. Twenty clinical participants with a psychosis-spectrum diagnosis and twenty controls were studied over six consecutive days using the experience sampling method (ESM). The findings revealed that fluctuations in attachment insecurity were significantly higher in the clinical group, that elevated stress predicted a subsequent increase in attachment insecurity, and that elevated attachment insecurity predicted a subsequent increase in paranoia; this effect was not observed in auditory hallucinations once co-occurring symptoms were controlled for. Finally, although previous ESM studies have shown that low self-esteem precedes the occurrence of paranoia, attachment insecurity continued to predict paranoia even when self-esteem was controlled for. The findings suggest that attachment security may be associated with a lower risk of paranoia, and that psychological interventions should address attachment beliefs and work towards establishing a sense of attachment security. Copyright © 2016. Published by Elsevier Ireland Ltd.

Attachment theory and psychoanalysis: some remarks from an epistemological and from a Freudian viewpoint.

PubMed

Zepf, Siegfried

2006-12-01

The author examines Bowlby's attachment theory and more recent versions of it from an epistemological viewpoint and subjects it to questioning on whether they are in line with central concepts of Freudian psychoanalysis. He argues that Bowlby's basic tenets regarding attachment theory, which later attachment theorists never seriously questioned, do not conform to scientific standards, and that psychoanalytic issues such as the dynamic unconscious, internal conflicts, interaction of drive wishes and the role of defence in establishing substitutive formations are either ignored or not treated in sufficient depth. In the light of this, Fonagy's assertion that psychoanalytic criticism of attachment theory arose from mutual misunderstandings and ought nowadays to be seen as outdated is reversed: psychoanalytic criticism can only be regarded as outdated if either basic tenets of Freudian psychoanalysis, or attachment theory or both are misunderstood.

Damping Effects of Drogue Parachutes on Orion Crew Module Dynamics

NASA Technical Reports Server (NTRS)

Aubuchon, Vanessa V.; Owens, D. Bruce

2016-01-01

Because simulations of the Orion Crew Module (CM) dynamics with drogue parachutes deployed were under-predicting the amount of damping seen in free-flight tests, an attach-point damping model was applied to the Orion system. A key hypothesis in this model is that the drogue parachutes' net load vector aligns with the CM drogue attachment point velocity vector. This assumption seems reasonable and has historically produced good results, but has never been experimentally verified. The wake of the CM influences the drogue parachutes, which makes performance predictions of the parachutes difficult. Many of these effects are not currently modeled in the simulations. A forced oscillation test of the CM with parachutes was conducted in the NASA LaRC 20-Ft Vertical Spin Tunnel (VST) to gather additional data to validate and refine the attach-point damping model. A second loads balance was added to the original Orion VST model to measure the drogue parachute loads independently of the CM. The objective of the test was to identify the contribution of the drogues to CM damping and provide additional information to quantify wake effects and the interactions between the CM and parachutes. The drogue parachute force vector was shown to be highly dependent on the CM wake characteristics. Based on these wind tunnel test data, the attach-point damping model was determined to be a sufficient approximation of the parachute dynamics in relationship to the CM dynamics for preliminary entry vehicle system design. More wake effects should be included to better model the system.

Biofilm attachment reduction on bioinspired, dynamic, micro-wrinkling surfaces

NASA Astrophysics Data System (ADS)

Epstein, Alexander K.; Hong, Donggyoon; Kim, Philseok; Aizenberg, Joanna

2013-09-01

Most bacteria live in multicellular communities known as biofilms that are adherent to surfaces in our environment, from sea beds to plumbing systems. Biofilms are often associated with clinical infections, nosocomial deaths and industrial damage such as bio-corrosion and clogging of pipes. As mature biofilms are extremely challenging to eradicate once formed, prevention is advantageous over treatment. However, conventional surface chemistry strategies are either generally transient, due to chemical masking, or toxic, as in the case of leaching marine antifouling paints. Inspired by the nonfouling skins of echinoderms and other marine organisms, which possess highly dynamic surface structures that mechanically frustrate bio-attachment, we have developed and tested a synthetic platform based on both uniaxial mechanical strain and buckling-induced elastomer microtopography. Bacterial biofilm attachment to the dynamic substrates was studied under an array of parameters, including strain amplitude and timescale (1-100 mm s-1), surface wrinkle length scale, bacterial species and cell geometry, and growth time. The optimal conditions for achieving up to ˜ 80% Pseudomonas aeruginosa biofilm reduction after 24 h growth and ˜ 60% reduction after 48 h were combinatorially elucidated to occur at 20% strain amplitude, a timescale of less than ˜ 5 min between strain cycles and a topography length scale corresponding to the cell dimension of ˜ 1 μm. Divergent effects on the attachment of P. aeruginosa, Staphylococcus aureus and Escherichia coli biofilms showed that the dynamic substrate also provides a new means of species-specific biofilm inhibition, or inversely, selection for a desired type of bacteria, without reliance on any toxic or transient surface chemical treatments.

Use of soil moisture dynamics and patterns at different spatio-temporal scales for the investigation of subsurface flow processes

NASA Astrophysics Data System (ADS)

Blume, T.; Zehe, E.; Bronstert, A.

2009-07-01

Spatial patterns as well as temporal dynamics of soil moisture have a major influence on runoff generation. The investigation of these dynamics and patterns can thus yield valuable information on hydrological processes, especially in data scarce or previously ungauged catchments. The combination of spatially scarce but temporally high resolution soil moisture profiles with episodic and thus temporally scarce moisture profiles at additional locations provides information on spatial as well as temporal patterns of soil moisture at the hillslope transect scale. This approach is better suited to difficult terrain (dense forest, steep slopes) than geophysical techniques and at the same time less cost-intensive than a high resolution grid of continuously measuring sensors. Rainfall simulation experiments with dye tracers while continuously monitoring soil moisture response allows for visualization of flow processes in the unsaturated zone at these locations. Data was analyzed at different spacio-temporal scales using various graphical methods, such as space-time colour maps (for the event and plot scale) and binary indicator maps (for the long-term and hillslope scale). Annual dynamics of soil moisture and decimeter-scale variability were also investigated. The proposed approach proved to be successful in the investigation of flow processes in the unsaturated zone and showed the importance of preferential flow in the Malalcahuello Catchment, a data-scarce catchment in the Andes of Southern Chile. Fast response times of stream flow indicate that preferential flow observed at the plot scale might also be of importance at the hillslope or catchment scale. Flow patterns were highly variable in space but persistent in time. The most likely explanation for preferential flow in this catchment is a combination of hydrophobicity, small scale heterogeneity in rainfall due to redistribution in the canopy and strong gradients in unsaturated conductivities leading to self-reinforcing flow paths.

Gelation-driven component selection in the generation of constitutional dynamic hydrogels based on guanine-quartet formation

PubMed Central

Sreenivasachary, Nampally; Lehn, Jean-Marie

2005-01-01

The guanosine hydrazide 1 yields a stable supramolecular hydrogel based on the formation of a guanine quartet (G-quartet) in presence of metal cations. The effect of various parameters (concentration, nature of metal ion, and temperature) on the properties of this gel has been studied. Proton NMR spectroscopy is shown to allow a molecular characterization of the gelation process. Hydrazide 1 and its assemblies can be reversibly decorated by acylhydrazone formation with various aldehydes, resulting in formation of highly viscous dynamic hydrogels. When a mixture of aldehydes is used, the dynamic system selects the aldehyde that leads to the most stable gel. Mixing hydrazides 1, 9 and aldehydes 6, 8 in 1:1:1:1 ratio generated a constitutional dynamic library containing the four acylhydrazone derivatives A, B, C, and D. The library constitution displayed preferential formation of the acylhydrazone B that yields the strongest gel. Thus, gelation redirects the acylhydrazone distribution in the dynamic library as guanosine hydrazide 1 scavenges preferentially aldehyde 8, under the pressure of gelation because of the collective interactions in the assemblies of G-quartets B, despite the strong preference of the competing hydrazide 9 for 8. Gel formation and component selection are thermoreversible. The process amounts to gelation-driven self-organization with component selection and amplification in constitutional dynamic hydrogels based on G-quartet formation and reversible covalent connections. The observed self-organization and component selection occur by means of a multilevel self-assembly involving three dynamic processes, two of supramolecular and one of reversible covalent nature. They extend constitutional dynamic chemistry to phase-organization and phase-transition events. PMID:15840720

Gelation-driven component selection in the generation of constitutional dynamic hydrogels based on guanine-quartet formation.

PubMed

Sreenivasachary, Nampally; Lehn, Jean-Marie

2005-04-26

The guanosine hydrazide 1 yields a stable supramolecular hydrogel based on the formation of a guanine quartet (G-quartet) in presence of metal cations. The effect of various parameters (concentration, nature of metal ion, and temperature) on the properties of this gel has been studied. Proton NMR spectroscopy is shown to allow a molecular characterization of the gelation process. Hydrazide 1 and its assemblies can be reversibly decorated by acylhydrazone formation with various aldehydes, resulting in formation of highly viscous dynamic hydrogels. When a mixture of aldehydes is used, the dynamic system selects the aldehyde that leads to the most stable gel. Mixing hydrazides 1, 9 and aldehydes 6, 8 in 1:1:1:1 ratio generated a constitutional dynamic library containing the four acylhydrazone derivatives A, B, C, and D. The library constitution displayed preferential formation of the acylhydrazone B that yields the strongest gel. Thus, gelation redirects the acylhydrazone distribution in the dynamic library as guanosine hydrazide 1 scavenges preferentially aldehyde 8, under the pressure of gelation because of the collective interactions in the assemblies of G-quartets B, despite the strong preference of the competing hydrazide 9 for 8. Gel formation and component selection are thermoreversible. The process amounts to gelation-driven self-organization with component selection and amplification in constitutional dynamic hydrogels based on G-quartet formation and reversible covalent connections. The observed self-organization and component selection occur by means of a multilevel self-assembly involving three dynamic processes, two of supramolecular and one of reversible covalent nature. They extend constitutional dynamic chemistry to phase-organization and phase-transition events.

Predictive Models for Tomato Spotted Wilt Virus Spread Dynamics, Considering Frankliniella occidentalis Specific Life Processes as Influenced by the Virus

PubMed Central

Ogada, Pamella Akoth; Moualeu, Dany Pascal; Poehling, Hans-Michael

2016-01-01

Several models have been studied on predictive epidemics of arthropod vectored plant viruses in an attempt to bring understanding to the complex but specific relationship between the three cornered pathosystem (virus, vector and host plant), as well as their interactions with the environment. A large body of studies mainly focuses on weather based models as management tool for monitoring pests and diseases, with very few incorporating the contribution of vector’s life processes in the disease dynamics, which is an essential aspect when mitigating virus incidences in a crop stand. In this study, we hypothesized that the multiplication and spread of tomato spotted wilt virus (TSWV) in a crop stand is strongly related to its influences on Frankliniella occidentalis preferential behavior and life expectancy. Model dynamics of important aspects in disease development within TSWV-F. occidentalis-host plant interactions were developed, focusing on F. occidentalis’ life processes as influenced by TSWV. The results show that the influence of TSWV on F. occidentalis preferential behaviour leads to an estimated increase in relative acquisition rate of the virus, and up to 33% increase in transmission rate to healthy plants. Also, increased life expectancy; which relates to improved fitness, is dependent on the virus induced preferential behaviour, consequently promoting multiplication and spread of the virus in a crop stand. The development of vector–based models could further help in elucidating the role of tri-trophic interactions in agricultural disease systems. Use of the model to examine the components of the disease process could also boost our understanding on how specific epidemiological characteristics interact to cause diseases in crops. With this level of understanding we can efficiently develop more precise control strategies for the virus and the vector. PMID:27159134

Predictive Models for Tomato Spotted Wilt Virus Spread Dynamics, Considering Frankliniella occidentalis Specific Life Processes as Influenced by the Virus.

PubMed

Ogada, Pamella Akoth; Moualeu, Dany Pascal; Poehling, Hans-Michael

2016-01-01

Several models have been studied on predictive epidemics of arthropod vectored plant viruses in an attempt to bring understanding to the complex but specific relationship between the three cornered pathosystem (virus, vector and host plant), as well as their interactions with the environment. A large body of studies mainly focuses on weather based models as management tool for monitoring pests and diseases, with very few incorporating the contribution of vector's life processes in the disease dynamics, which is an essential aspect when mitigating virus incidences in a crop stand. In this study, we hypothesized that the multiplication and spread of tomato spotted wilt virus (TSWV) in a crop stand is strongly related to its influences on Frankliniella occidentalis preferential behavior and life expectancy. Model dynamics of important aspects in disease development within TSWV-F. occidentalis-host plant interactions were developed, focusing on F. occidentalis' life processes as influenced by TSWV. The results show that the influence of TSWV on F. occidentalis preferential behaviour leads to an estimated increase in relative acquisition rate of the virus, and up to 33% increase in transmission rate to healthy plants. Also, increased life expectancy; which relates to improved fitness, is dependent on the virus induced preferential behaviour, consequently promoting multiplication and spread of the virus in a crop stand. The development of vector-based models could further help in elucidating the role of tri-trophic interactions in agricultural disease systems. Use of the model to examine the components of the disease process could also boost our understanding on how specific epidemiological characteristics interact to cause diseases in crops. With this level of understanding we can efficiently develop more precise control strategies for the virus and the vector.

Lesions of the dopaminergic innervation of the nucleus accumbens medial shell delay the generation of preference for sucrose, but not of sexual pheromones.

PubMed

Martínez-Hernández, José; Lanuza, Enrique; Martínez-García, Fernando

2012-01-15

Male sexual pheromones are rewarding stimuli for female mice, able to induce conditioned place preference. To test whether processing these natural reinforcing stimuli depends on the dopaminergic innervation of the nucleus accumbens, as for other natural rewards, we compare the effects of specific lesions of the dopaminergic innervation of the medial shell of the nucleus accumbens on two different appetitive behaviours, 'pheromone seeking' and sucrose preferential intake. Female mice, with no previous experience with either adult male chemical stimuli or with sucrose, received injections of 6-hydroxydopamine (or vehicle) in the medial shell of the accumbens. Then, we analyzed their preference for male soiled-bedding and their preferential intake of a sucrose solution, with particular emphasis on the dynamics of acquisition of both natural rewards. The results indicate that both lesioned and sham animals showed similar preference for male sexual pheromones, which was constant along the test (linear dynamics). In contrast, lesioned animals differed from sham operated mice in the dynamics of sucrose consumption in their first test of sucrose preference. Sham animals showed an initial sucrose preference followed by preference for water, which can be interpreted as sucrose neophobia. Lesioned animals showed no preference at the beginning of the test, and a delayed sucrose preference appeared followed by a delayed neophobia. The next day, during a second sucrose-preference test, both groups displayed comparable and sustained preferential sucrose intake. Therefore, dopamine in the medial shell of the nucleus accumbens has a different role on the reward of sexual pheromones and sucrose. Copyright © 2011 Elsevier B.V. All rights reserved.

Random-growth urban model with geographical fitness

NASA Astrophysics Data System (ADS)

Kii, Masanobu; Akimoto, Keigo; Doi, Kenji

2012-12-01

This paper formulates a random-growth urban model with a notion of geographical fitness. Using techniques of complex-network theory, we study our system as a type of preferential-attachment model with fitness, and we analyze its macro behavior to clarify the properties of the city-size distributions it predicts. First, restricting the geographical fitness to take positive values and using a continuum approach, we show that the city-size distributions predicted by our model asymptotically approach Pareto distributions with coefficients greater than unity. Then, allowing the geographical fitness to take negative values, we perform local coefficient analysis to show that the predicted city-size distributions can deviate from Pareto distributions, as is often observed in actual city-size distributions. As a result, the model we propose can generate a generic class of city-size distributions, including but not limited to Pareto distributions. For applications to city-population projections, our simple model requires randomness only when new cities are created, not during their subsequent growth. This property leads to smooth trajectories of city population growth, in contrast to other models using Gibrat’s law. In addition, a discrete form of our dynamical equations can be used to estimate past city populations based on present-day data; this fact allows quantitative assessment of the performance of our model. Further study is needed to determine appropriate formulas for the geographical fitness.

An Application of Attachment Theory: Mentoring Relationship Dynamics and Ethical Concerns

ERIC Educational Resources Information Center

Gormley, Barbara

2008-01-01

In this theoretical paper, mentoring relationships are conceptualized as close relationships that occur along a spectrum from highly functional to highly dysfunctional, with most occurring in between. A complex set of factors describe the functioning level of mentoring relationships: (a) the attachment styles of the mentors and mentees; (b)…

Remote Control over Underwater Dynamic Attachment/Detachment and Locomotion.

PubMed

Ma, Yanfei; Ma, Shuanhong; Wu, Yang; Pei, Xiaowei; Gorb, Stanislav N; Wang, Zuankai; Liu, Weimin; Zhou, Feng

2018-06-19

Despite extensive efforts to mimic the fascinating adhesion capability of geckos, the development of reversible adhesives underwater has long been lagging. The appearance of mussels-inspired dopamine chemistry has provided the feasibility to fabricate underwater adhesives; however, for such a system, imitating the reversible and fast dynamic attachment/detachment mechanism of gecko feet still remains unsolved. Here, by synthesizing a thermoresponsive copolymer of poly(dopamine methacrylamide-co-methoxyethyl-acrylate-co-N-isopropyl acrylamide) and then decorating it onto mushroom-shaped poly(dimethylsiloxane) pillar arrays, a novel underwater thermoresponsive gecko-like adhesive (TRGA) can be fabricated, yielding high adhesion during the attachment state above the lower critical solution temperature (LCST) of the copolymer, yet low adhesion during the detachment state below the LCST of the copolymer. By integrating the Fe 3 O 4 nanoparticles into the TRGA, TRGAs responsive to near-infrared laser radiation can be engineered, which can be successfully used for rapid and reversible remote control over adhesion so as to capture and release heavy objects underwater because of the contrast force change of both the normal adhesion force and the lateral friction force. It is also demonstrated that the material can be assembled on the tracks of an underwater mobile device to realize controllable movement. This opens up the door for developing intelligent underwater gecko-like locomotion with dynamic attachment/detachment ability. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Topography on a subcellular scale modulates cellular adhesions and actin stress fiber dynamics in tumor associated fibroblasts

NASA Astrophysics Data System (ADS)

Azatov, Mikheil; Sun, Xiaoyu; Suberi, Alexandra; Fourkas, John T.; Upadhyaya, Arpita

2017-12-01

Cells can sense and adapt to mechanical properties of their environment. The local geometry of the extracellular matrix, such as its topography, has been shown to modulate cell morphology, migration, and proliferation. Here we investigate the effect of micro/nanotopography on the morphology and cytoskeletal dynamics of human pancreatic tumor-associated fibroblast cells (TAFs). We use arrays of parallel nanoridges with variable spacings on a subcellular scale to investigate the response of TAFs to the topography of their environment. We find that cell shape and stress fiber organization both align along the direction of the nanoridges. Our analysis reveals a strong bimodal relationship between the degree of alignment and the spacing of the nanoridges. Furthermore, focal adhesions align along ridges and form preferentially on top of the ridges. Tracking actin stress fiber movement reveals enhanced dynamics of stress fibers on topographically patterned surfaces. We find that components of the actin cytoskeleton move preferentially along the ridges with a significantly higher velocity along the ridges than on a flat surface. Our results suggest that a complex interplay between the actin cytoskeleton and focal adhesions coordinates the cellular response to micro/nanotopography.

Attached cavitation at a small diameter ultrasonic horn tip

NASA Astrophysics Data System (ADS)

Žnidarčič, Anton; Mettin, Robert; Cairós, Carlos; Dular, Matevž

2014-02-01

Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids, for instance, for cell disruption or sonochemical reactions. They are operated typically in the frequency range up to about 50 kHz and have tip diameters from some mm to several cm. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e., below the acoustic driving frequency. Here, we present a systematic study of the cavitation dynamics in water at a 20 kHz horn tip of 3 mm diameter. The system was investigated by high-speed imaging with simultaneous recording of the acoustic emissions. Measurements were performed under variation of acoustic power, air saturation, viscosity, surface tension, and temperature of the liquid. Our findings show that the liquid properties play no significant role in the dynamics of the attached cavitation at the small ultrasonic horn. Also the variation of the experimental geometry, within a certain range, did not change the dynamics. We believe that the main two reasons for the peculiar dynamics of cavitation on a small ultrasonic horn are the higher energy density on a small tip and the inability of the big tip to "wash" away the gaseous bubbles. Calculation of the somewhat adapted Strouhal number revealed that, similar to the hydrodynamic cavitation, values which are relatively low characterize slow cavitation structure dynamics. In cases where the cavitation follows the driving frequency this value lies much higher - probably at Str > 20. In the spirit to distinguish the observed phenomenon with other cavitation dynamics at ultrasonic transducer surfaces, we suggest to term the observed phenomenon of attached cavities partly covering the full horn tip as "acoustic supercavitation." This reflects the conjecture that not the sound field in terms of acoustic (negative) pressure in the liquid is responsible for nucleation, but the motion of the transducer surface.

Finite Element Model Development For Aircraft Fuselage Structures

NASA Technical Reports Server (NTRS)

Buehrle, Ralph D.; Fleming, Gary A.; Pappa, Richard S.; Grosveld, Ferdinand W.

2000-01-01

The ability to extend the valid frequency range for finite element based structural dynamic predictions using detailed models of the structural components and attachment interfaces is examined for several stiffened aircraft fuselage structures. This extended dynamic prediction capability is needed for the integration of mid-frequency noise control technology. Beam, plate and solid element models of the stiffener components are evaluated. Attachment models between the stiffener and panel skin range from a line along the rivets of the physical structure to a constraint over the entire contact surface. The finite element models are validated using experimental modal analysis results.

Inactivation of Escherichia coli O157:H7 attached to spinach harvester blade using bacteriophage.

PubMed

Patel, Jitendra; Sharma, Manan; Millner, Patricia; Calaway, Todd; Singh, Manpreet

2011-04-01

Outbreaks associated with leafy greens have focused attention on the transfer of human pathogens to these commodities during harvest with commercial equipment. Attachment of Escherichia coli O157:H7 on new or rusty spinach harvester blades immersed in spinach extract or 10% tryptic soy broth (TSB) was investigated. Bacteriophages specific for E. coli O157:H7 were evaluated to kill cells attached to blade. A cocktail of five nalidixic acid-resistant E. coli O157:H7 isolates was transferred to 25 mL of spinach extract or 10% TSB. A piece of sterilized spinach harvester blade (2×1") was placed in above spinach extract or 10% TSB and incubated at room (22 °C) or dynamic (30 °C day, 20 °C night) temperatures. E. coli O157:H7 populations attached to blade during incubation in spinach extract or 10% TSB were determined. When inoculated at 1 log CFU/mL, E. coli O157:H7 attachment to blades after 24 and 48 h incubation at dynamic temperature (6.09 and 6.37 log CFU/mL) was significantly higher than when incubated at 22 °C (4.84 and 5.68 log CFU/mL), respectively. After 48 h incubation, two blades were sprayed on each side with a cocktail of E. coli O157-specific bacteriophages before scraping the blade, and subsequent plating on Sorbitol MacConkey media-nalidixic acid. Application of bacteriophages reduced E. coli O157:H7 populations by 4.5 log CFU on blades after 2 h of phage treatment. Our study demonstrates that E. coli O157:H7 can attach to and proliferate on spinach harvester blades under static and dynamic temperature conditions, and bacteriophages are able to reduce E. coli O157:H7 populations adhered to blades. © Mary Ann Liebert, Inc.

Use of stable isotope analysis in determining aquatic food webs

EPA Science Inventory

Stable isotope analysis is a useful tool for describing resource-consumer dynamics in ecosystems. In general, organisms of a given trophic level or functional feeding group will have a stable isotope ratio identifiable different than their prey because of preferential use of one ...

Myc Dynamically and Preferentially Relocates to a Transcription Factory Occupied by Igh

PubMed Central

Osborne, Cameron S; Chakalova, Lyubomira; Mitchell, Jennifer A; Horton, Alice; Wood, Andrew L; Bolland, Daniel J; Corcoran, Anne E; Fraser, Peter

2007-01-01

Transcription in mammalian nuclei is highly compartmentalized in RNA polymerase II-enriched nuclear foci known as transcription factories. Genes in cis and trans can share the same factory, suggesting that genes migrate to preassembled transcription sites. We used fluorescent in situ hybridization to investigate the dynamics of gene association with transcription factories during immediate early (IE) gene induction in mouse B lymphocytes. Here, we show that induction involves rapid gene relocation to transcription factories. Importantly, we find that the Myc proto-oncogene on Chromosome 15 is preferentially recruited to the same transcription factory as the highly transcribed Igh gene located on Chromosome 12. Myc and Igh are the most frequent translocation partners in plasmacytoma and Burkitt lymphoma. Our results show that transcriptional activation of IE genes involves rapid relocation to preassembled transcription factories. Furthermore, the data imply a direct link between the nonrandom interchromosomal organization of transcribed genes at transcription factories and the incidence of specific chromosomal translocations. PMID:17622196

Short-ranged memory model with preferential growth

NASA Astrophysics Data System (ADS)

Schaigorodsky, Ana L.; Perotti, Juan I.; Almeira, Nahuel; Billoni, Orlando V.

2018-02-01

In this work we introduce a variant of the Yule-Simon model for preferential growth by incorporating a finite kernel to model the effects of bounded memory. We characterize the properties of the model combining analytical arguments with extensive numerical simulations. In particular, we analyze the lifetime and popularity distributions by mapping the model dynamics to corresponding Markov chains and branching processes, respectively. These distributions follow power laws with well-defined exponents that are within the range of the empirical data reported in ecologies. Interestingly, by varying the innovation rate, this simple out-of-equilibrium model exhibits many of the characteristics of a continuous phase transition and, around the critical point, it generates time series with power-law popularity, lifetime and interevent time distributions, and nontrivial temporal correlations, such as a bursty dynamics in analogy with the activity of solar flares. Our results suggest that an appropriate balance between innovation and oblivion rates could provide an explanatory framework for many of the properties commonly observed in many complex systems.

Short-ranged memory model with preferential growth.

PubMed

Schaigorodsky, Ana L; Perotti, Juan I; Almeira, Nahuel; Billoni, Orlando V

2018-02-01

In this work we introduce a variant of the Yule-Simon model for preferential growth by incorporating a finite kernel to model the effects of bounded memory. We characterize the properties of the model combining analytical arguments with extensive numerical simulations. In particular, we analyze the lifetime and popularity distributions by mapping the model dynamics to corresponding Markov chains and branching processes, respectively. These distributions follow power laws with well-defined exponents that are within the range of the empirical data reported in ecologies. Interestingly, by varying the innovation rate, this simple out-of-equilibrium model exhibits many of the characteristics of a continuous phase transition and, around the critical point, it generates time series with power-law popularity, lifetime and interevent time distributions, and nontrivial temporal correlations, such as a bursty dynamics in analogy with the activity of solar flares. Our results suggest that an appropriate balance between innovation and oblivion rates could provide an explanatory framework for many of the properties commonly observed in many complex systems.

Application of adult attachment theory to group member transference and the group therapy process.

PubMed

Markin, Rayna D; Marmarosh, Cheri

2010-03-01

Although clinical researchers have applied attachment theory to client conceptualization and treatment in individual therapy, few researchers have applied this theory to group therapy. The purpose of this article is to begin to apply theory and research on adult dyadic and group attachment styles to our understanding of group dynamics and processes in adult therapy groups. In particular, we set forth theoretical propositions on how group members' attachment styles affect relationships within the group. Specifically, this article offers some predictions on how identifying group member dyadic and group attachment styles could help leaders predict member transference within the therapy group. Implications of group member attachment for the selection and composition of a group and the different group stages are discussed. Recommendations for group clinicians and researchers are offered. PsycINFO Database Record (c) 2010 APA, all rights reserved

Infant bonding and attachment to the caregiver: Insights from basic and clinical science

PubMed Central

Sullivan, Regina; Perry, Rosemarie; Sloan, Aliza; Kleinhaus, Karine; Burtchen, Nina

2011-01-01

The bonding and early life attachment between the infant and caregiver is a dynamic, bidirectional process involving caregiver nurturing of the infant, as well as complementary infant behavior that elicits parental care. Attachment appears to have a dual function. The first function is to ensure the infant remains close to the caregiver in order to receive necessary care for survival. Interestingly, animal research has shown that both nurturing and painful stimuli associated with the caregiver support attachment. Secondly, the quality of attachment and its associated sensory stimuli organize the brain to define the infant's cognitive and emotional development. Specifically, the patterning and quality of care regulate the infant's brain function and behavioral expression that determines long-term emotional regulation. These issues, presented within an historical view of infant attachment, highlight the importance of integrating human and animal research in understanding infant care. PMID:22107895

Molecular dynamics simulations study of nano bubble attachment at hydrophobic surfaces

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

Jin, Jiaqi; Dang, Liem X.; Miller, Jan D.

Bubble attachment phenomena are examined using Molecular Dynamics Simulations (MDS) for the first time. The simulation involves a nitrogen nano bubble containing 906 nitrogen molecules in a water phase with 74,000 water molecules at molybdenite surfaces. During a simulation period of 1 ns, film rupture and displacement occurs. The attached nanobubble at the hydrophobic molybdenite face surface results in a contact angle of about 90º. This spontaneous attachment is due to a “water exclusion zone” at the molybdenite face surface and can be explained by a van der Waals (vdW) attractive force, as discussed in the literature. In contrast, themore » film is stable at the hydrophilic quartz (001) surface and the bubble does not attach. Contact angles determined from MD simulations are reported, and these results agree well with experimental and MDS sessile drop results. In this way, film stability and bubble attachment are described with respect to interfacial water structure for surfaces of different polarity. Interfacial water molecules at the hydrophobic molybdenite face surface have relatively weak interactions with the surface when compared to the hydrophilic quartz (001) surface, as revealed by the presence of a 3 Å “water exclusion zone” at the molybdenite/water interface. The molybdenite armchair-edge and zigzag-edge surfaces show a comparably slow process for film rupture and displacement when compared to the molybdenite face surface, which is consistent with their relatively weak hydrophobic character.« less

Modeling Dynamic Evolution of Online Friendship Network

NASA Astrophysics Data System (ADS)

Wu, Lian-Ren; Yan, Qiang

2012-10-01

In this paper, we study the dynamic evolution of friendship network in SNS (Social Networking Site). Our analysis suggests that an individual joining a community depends not only on the number of friends he or she has within the community, but also on the friendship network generated by those friends. In addition, we propose a model which is based on two processes: first, connecting nearest neighbors; second, strength driven attachment mechanism. The model reflects two facts: first, in the social network it is a universal phenomenon that two nodes are connected when they have at least one common neighbor; second, new nodes connect more likely to nodes which have larger weights and interactions, a phenomenon called strength driven attachment (also called weight driven attachment). From the simulation results, we find that degree distribution P(k), strength distribution P(s), and degree-strength correlation are all consistent with empirical data.

Embedded function methods for compressible high speed turbulent flow

NASA Technical Reports Server (NTRS)

Walker, J. D. A.

1989-01-01

Fundamental issues relating to compressible turbulent flow are addressed. The focus has been on developing methods and testing concepts for attached flows rather than trying to force a conventional law of the wall into a zone of backflow. Although the dynamics of the near-wall flow in an attached turbulent boundary layer are relatively well documented, the dynamical features of a zone of reversed turbulent flow are not, nor are they well understood. Incompressibility introduces effects and issues that have been dealt with only marginally in the literature, therefore, the present work has been focussed on attached high-speed flows. The wall function method has been extended up through the supersonic to hypersonic speeds. Algorithms have been successfully introduced into the code that calculates the flow all the way to the wall, and testing is being carried out for progressively more complex flow situations.

A molecular dynamics simulation of solvent effects on the crystal morphology of HMX.

PubMed

Duan, Xiaohui; Wei, Chunxue; Liu, Yonggang; Pei, Chonghua

2010-02-15

The solvent has a large effect on the crystal morphology of the organic explosive compound octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX, C(4)H(8)N(8)O(8)). The attachment energy calculations predict a growth morphology in vacuum dominated by (020), (011), (102 ), (111 ) and (100) crystal forms. Molecular dynamics simulations are performed for these crystal faces of HMX in contact with acetone solvent. A corrected attachment energy model, accounting for the surface chemistry and the associated topography (step structure) of the habit crystal plane, is applied to predict the morphological importance of a crystal surface in solvent. From the solvent-effected attachment energy calculations it follows that the (100) face becomes morphologically more important compared with that in vacuum, while the (020) and (102 ) are not visible at all. This agrees well with the observed experimental HMX morphology grown from the acetone solution.

The response dynamics of preferential choice.

PubMed

Koop, Gregory J; Johnson, Joseph G

2013-12-01

The ubiquity of psychological process models requires an increased degree of sophistication in the methods and metrics that we use to evaluate them. We contribute to this venture by capitalizing on recent work in cognitive science analyzing response dynamics, which shows that the bearing information processing dynamics have on intended action is also revealed in the motor system. This decidedly "embodied" view suggests that researchers are missing out on potential dependent variables with which to evaluate their models-those associated with the motor response that produces a choice. The current work develops a method for collecting and analyzing such data in the domain of decision making. We first validate this method using widely normed stimuli from the International Affective Picture System (Experiment 1), and demonstrate that curvature in response trajectories provides a metric of the competition between choice options. We next extend the method to risky decision making (Experiment 2) and develop predictions for three popular classes of process model. The data provided by response dynamics demonstrate that choices contrary to the maxim of risk seeking in losses and risk aversion in gains may be the product of at least one "online" preference reversal, and can thus begin to discriminate amongst the candidate models. Finally, we incorporate attentional data collected via eye-tracking (Experiment 3) to develop a formal computational model of joint information sampling and preference accumulation. In sum, we validate response dynamics for use in preferential choice tasks and demonstrate the unique conclusions afforded by response dynamics over and above traditional methods. Copyright © 2013 Elsevier Inc. All rights reserved.

A generalized preferential attachment model for business firms growth rates. I. Empirical evidence

NASA Astrophysics Data System (ADS)

Pammolli, F.; Fu, D.; Buldyrev, S. V.; Riccaboni, M.; Matia, K.; Yamasaki, K.; Stanley, H. E.

2007-05-01

We introduce a model of proportional growth to explain the distribution P(g) of business firm growth rates. The model predicts that P(g) is Laplace in the central part and depicts an asymptotic power-law behavior in the tails with an exponent ζ = 3. Because of data limitations, previous studies in this field have been focusing exclusively on the Laplace shape of the body of the distribution. We test the model at different levels of aggregation in the economy, from products, to firms, to countries, and we find that the predictions are in good agreement with empirical evidence on both growth distributions and size-variance relationships.

From the Cover: The growth of business firms: Theoretical framework and empirical evidence

NASA Astrophysics Data System (ADS)

Fu, Dongfeng; Pammolli, Fabio; Buldyrev, S. V.; Riccaboni, Massimo; Matia, Kaushik; Yamasaki, Kazuko; Stanley, H. Eugene

2005-12-01

We introduce a model of proportional growth to explain the distribution Pg(g) of business-firm growth rates. The model predicts that Pg(g) is exponential in the central part and depicts an asymptotic power-law behavior in the tails with an exponent = 3. Because of data limitations, previous studies in this field have been focusing exclusively on the Laplace shape of the body of the distribution. In this article, we test the model at different levels of aggregation in the economy, from products to firms to countries, and we find that the predictions of the model agree with empirical growth distributions and size-variance relationships. proportional growth | preferential attachment | Laplace distribution

Fitness model for the Italian interbank money market.

PubMed

De Masi, G; Iori, G; Caldarelli, G

2006-12-01

We use the theory of complex networks in order to quantitatively characterize the formation of communities in a particular financial market. The system is composed by different banks exchanging on a daily basis loans and debts of liquidity. Through topological analysis and by means of a model of network growth we can determine the formation of different group of banks characterized by different business strategy. The model based on Pareto's law makes no use of growth or preferential attachment and it reproduces correctly all the various statistical properties of the system. We believe that this network modeling of the market could be an efficient way to evaluate the impact of different policies in the market of liquidity.

Occurrence of the Leech, Pontobdella muricata Linnaeus, on Elasmobranch Species in the Northern and Central Adriatic Sea.

PubMed

Bolognini, Luca; Leoni, Simone; Polidori, Piero; Grati, Fabio; Scarcella, Giuseppe; Pellini, Giulio; Domenichetti, Filippo; Ferrà, Carmen; Fabi, Gianna

2016-12-01

This study provides a parasitological analysis of the elasmobranch species caught in the northern and central Adriatic Sea. Sixty-two marine leeches were recorded on 747 individuals of Raja clavata Linnaeus, 1758 (thornback ray), Myliobatis aquila Linnaeus, 1758 (common eagle ray), and Torpedo marmorata Risso, 1810 (marbled torpedo ray) caught in 56 hauls over a 5 yr period. All leeches were identified as Pontobdella muricata, which is a typical ectoparasite of benthic elasmobranchs. The prevalence of infection ranged from 7.11% on R. clavata to 12.00% on M. aquila. The intensity of infection, the preferential sites of attachment to the host, and the periodicity of infection were evaluated.

Numerical simulation of axisymmetric valve operation for different outer cone angle

NASA Astrophysics Data System (ADS)

Smyk, Emil

One of the method of flow separation control is application of axisymmetric valve. It is composed of nozzle with core. Normally the main flow is attached to inner cone and flow by preferential collector to primary flow pipe. If through control nozzle starts flow jet (control jet) the main flow is switched to annular secondary collector. In both situation the main flow is deflected to inner or outer cone (placed at the outlet of the valve's nozzle) by Coanda effect. The paper deals with the numerical simulation of this axisymetric annular nozzle with integrated synthetic jet actuator. The aim of the work is influence examination of outer cone angle on deflection on main stream.

Modeling online social signed networks

NASA Astrophysics Data System (ADS)

Li, Le; Gu, Ke; Zeng, An; Fan, Ying; Di, Zengru

2018-04-01

People's online rating behavior can be modeled by user-object bipartite networks directly. However, few works have been devoted to reveal the hidden relations between users, especially from the perspective of signed networks. We analyze the signed monopartite networks projected by the signed user-object bipartite networks, finding that the networks are highly clustered with obvious community structure. Interestingly, the positive clustering coefficient is remarkably higher than the negative clustering coefficient. Then, a Signed Growing Network model (SGN) based on local preferential attachment is proposed to generate a user's signed network that has community structure and high positive clustering coefficient. Other structural properties of the modeled networks are also found to be similar to the empirical networks.

Relationship between attachment style and symptom severity across the psychosis spectrum: A meta-analysis.

PubMed

Carr, Sarah Christina; Hardy, Amy; Fornells-Ambrojo, Miriam

2018-02-01

There is growing evidence for the role of attachment in psychosis, however, to date there has been no quantitative review of the prevalence of insecure attachment in psychosis. The current study sought to systematically appraise studies investigating the prevalence of insecure attachment and the association with psychosis-spectrum experiences using meta-analytic techniques. A systematic search of studies carried out between January 1980 and 30th November 2015 found 25 papers eligible for inclusion. The meta-analysis showed that the prevalence of insecure attachment style was significantly higher in individuals with psychosis (76%) than in non-clinical samples (38%), with fearful attachment being the most prevalent. Across the continuum, there was a small but significant relationship between positive symptom severity and insecure attachment and a significant relationship between negative symptom severity and insecure attachment in the non-clinical analysis. This relationship was not found in the clinical group. The prevalence of insecure attachment appears to be high in psychosis, however, the relationship between symptom severity and attachment is small. Attachment theory may provide greater understanding of the development of positive symptoms than previously thought, however, research needs to include more at-risk samples and longitudinal research to fully understand the dynamics of this relationship. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Mosasaur Tooth Attachment Apparatus as Paradigm for the Evolution of the Gnathostome Periodontium

PubMed Central

Luan, Xianghong; Walker, Cameron; Dangaria, Smit; Ito, Yoshihiro; Druzinsky, Robert; Jarosius, Kristina; Lesot, Herve; Rieppel, Olivier

2009-01-01

Vertebrate teeth are attached to jaws by a variety of mechanisms, including acrodont, pleurodont, and thecodont modes of attachment. Recent studies have suggested that various modes of attachment exist within each sub-category. Especially squamates feature a broad diversity of modes of attachment. Here we have investigated tooth attachment tissues in the late cretaceous mosasaur Clidastes and compared mosasaur tooth attachment with modes of attachment found in other extant reptiles. Using histologic analysis of ultrathin ground sections, four distinct mineralized tissues that anchor mosasaur teeth to the jaw were identified: (i) an acellular cementum layer at the interface between root and cellular cementum, (ii) a massive cone consisting of trabecular cellular cementum, (iii) the mineralized periodontal ligament containing mineralized Sharpey’s fibers, and (iv) the interdental ridges connecting adjacent teeth. The complex, multilayered attachment apparatus in mosasaurs was compared with attachment tissues in extant reptiles, including Iguana and Caiman. Based on our comparative analysis we postulate the presence of a quadruple-layer tissue architecture underlying reptilian tooth attachment, comprised of acellular cementum, cellular cementum, mineralized periodontal ligament, and interdental ridge (alveolar bone). We propose that the mineralization status of the periodontal ligament is a dynamic feature in vertebrate evolution subject to functional adaptation. PMID:19469852

Scaling and biomechanics of surface attachment in climbing animals

PubMed Central

Labonte, David; Federle, Walter

2015-01-01

Attachment devices are essential adaptations for climbing animals and valuable models for synthetic adhesives. A major unresolved question for both natural and bioinspired attachment systems is how attachment performance depends on size. Here, we discuss how contact geometry and mode of detachment influence the scaling of attachment forces for claws and adhesive pads, and how allometric data on biological systems can yield insights into their mechanism of attachment. Larger animals are expected to attach less well to surfaces, due to their smaller surface-to-volume ratio, and because it becomes increasingly difficult to distribute load uniformly across large contact areas. In order to compensate for this decrease of weight-specific adhesion, large animals could evolve overproportionally large pads, or adaptations that increase attachment efficiency (adhesion or friction per unit contact area). Available data suggest that attachment pad area scales close to isometry within clades, but pad efficiency in some animals increases with size so that attachment performance is approximately size-independent. The mechanisms underlying this biologically important variation in pad efficiency are still unclear. We suggest that switching between stress concentration (easy detachment) and uniform load distribution (strong attachment) via shear forces is one of the key mechanisms enabling the dynamic control of adhesion during locomotion. PMID:25533088

Why does high pressure destroy co-non-solvency of PNIPAm in aqueous methanol?

PubMed

de Oliveira, Tiago E; Netz, Paulo A; Mukherji, Debashish; Kremer, Kurt

2015-11-28

It is well known that poly(N-isopropylacrylamide) (PNIPAm) exhibits an interesting, yet puzzling, phenomenon of co-non-solvency. Co-non-solvency occurs when two competing good solvents for PNIPAm, such as water and alcohol, are mixed together. As a result, the same PNIPAm collapses within intermediate mixing ratios. This complex conformational transition is driven by preferential binding of methanol with PNIPAm. Interestingly, co-non-solvency can be destroyed when applying high hydrostatic pressures. In this work, using a large scale molecular dynamics simulation employing high pressures, we propose a microscopic picture behind the suppression of the co-non-solvency phenomenon. Based on thermodynamic and structural analysis, our results suggest that the preferential binding of methanol with PNIPAm gets partially lost at high pressures, making the background fluid reasonably homogeneous for the polymer. This is consistent with the hypothesis that the co-non-solvency phenomenon is driven by preferential binding and is not based on depletion effects.

The application of in situ analytical transmission electron microscopy to the study of preferential intergranular oxidation in Alloy 600.

PubMed

Burke, M G; Bertali, G; Prestat, E; Scenini, F; Haigh, S J

2017-05-01

In situ analytical transmission electron microscopy (TEM) can provide a unique perspective on dynamic reactions in a variety of environments, including liquids and gases. In this study, in situ analytical TEM techniques have been applied to examine the localised oxidation reactions that occur in a Ni-Cr-Fe alloy, Alloy 600, using a gas environmental cell at elevated temperatures. The initial stages of preferential intergranular oxidation, shown to be an important precursor phenomenon for intergranular stress corrosion cracking in pressurized water reactors (PWRs), have been successfully identified using the in situ approach. Furthermore, the detailed observations correspond to the ex situ results obtained from bulk specimens tested in hydrogenated steam and in high temperature PWR primary water. The excellent agreement between the in situ and ex situ oxidation studies demonstrates that this approach can be used to investigate the initial stages of preferential intergranular oxidation relevant to nuclear power systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Longitudinal Impact of Attachment-Related Risk and Exposure to Trauma among Young Children after Hurricane Katrina

ERIC Educational Resources Information Center

Osofsky, Joy; Kronenberg, Mindy; Bocknek, Erika; Hansel, Tonya Cross

2015-01-01

Background: Research suggests that young childhood is a dynamic developmental phase during which risks to attachment figures as well as traumatic events may be particularly important. The loss and disruption associated with Hurricane Katrina highlighted the vulnerabilities and special needs of young children exposed to natural disaster. Objective:…

CONCURRENT INJECTION OF COSOLVENT AND AIR FOR ENHANCED PCE REMOVAL

EPA Science Inventory

The goal of this study was to use preferential flow of air to improve the dynamics of cosolvent displacement in order to enhance DNAPL displacement and dissolution. The concurrent injection of cosolvent and air was evaluated in a glass micromodel for a DNAPL remediation technolog...

Space Shuttle Projects

NASA Image and Video Library

1978-09-01

This photograph shows stacking of the left side of the solid rocket booster (SRB) segments in the Dynamic Test Stand at the east test area of the Marshall Space Flight Center (MSFC). Staging shown here are the aft skirt, aft segment, and aft center segment. The SRB was attached to the external tank (ET) and then the orbiter later for the Mated Vertical Ground Vibration Test (MVGVT), that resumed in October 1978. The stacking of a complete Shuttle in the Dynamic Test Stand allowed test engineers to perform ground vibration testing on the Shuttle in its liftoff configuration. The purpose of the MVGVT is to verify that the Space Shuttle would perform as predicted during launch. The platforms inside the Dynamic Test Stand were modified to accommodate two SRB's to which the ET was attached.

Space Shuttle Projects

NASA Image and Video Library

1978-09-01

This photograph shows the left side of the solid rocket booster (SRB) segment as it awaits being mated to the nose cone and forward skirt in the Dynamic Test Stand at the east test area of the Marshall Space Flight Center (MSFC). The SRB would be attached to the external tank (ET) and then the orbiter later for the Mated Vertical Ground Vibration Test (MVGVT), that resumed in October 1978. The stacking of a complete Shuttle in the Dynamic Test Stand allowed test engineers to perform ground vibration testing on the Shuttle in its liftoff configuration. The purpose of the MVGVT was to verify that the Space Shuttle would perform as predicted during launch. The platforms inside the Dynamic Test Stand were modified to accommodate two SRB's to which the ET was attached.

Self-reported attachment patterns and Rorschach-related scores of ego boundary, defensive processes, and thinking disorders.

PubMed

Berant, Ety; Wald, Yaarit

2009-07-01

In this study, we addressed associations between self-reported attachment scales (anxiety and avoidance) and Rorschach (1921/1942) indexes indicating ego-boundary perception (barrier and penetration), use of projective identification, devaluation and splitting defenses, and Comprehensive System (Exner, 2005) scores that represent boundary blurring (incongruous and fabulized combinations). In this study, we extended the sample and findings described by Berant, Mikulincer, Shaver, and Segal (2005) using a nonclinical sample of 89 Israeli adults. We found significant associations between attachment orientations and Rorschach indexes dynamically related to anxiety. We also found a trend toward association between attachment orientation and avoidance. We discuss the theoretical and clinical implications of these findings.

A physicochemical investigation of membrane fouling in cold microfiltration of skim milk.

PubMed

Tan, T J; Wang, D; Moraru, C I

2014-01-01

The main challenge in microfiltration (MF) is membrane fouling, which leads to a significant decline in permeate flux and a change in membrane selectivity over time. This work aims to elucidate the mechanisms of membrane fouling in cold MF of skim milk by identifying and quantifying the proteins and minerals involved in external and internal membrane fouling. Microfiltration was conducted using a 1.4-μm ceramic membrane, at a temperature of 6±1°C, cross-flow velocity of 6m/s, and transmembrane pressure of 159kPa, for 90min. Internal and external foulants were extracted from a ceramic membrane both after a brief contact between the membrane and skim milk, to evaluate instantaneous adsorption of foulants, and after MF. Four foulant streams were collected: weakly attached external foulants, weakly attached internal foulants, strongly attached external foulants, and strongly attached internal foulants. Liquid chromatography coupled with tandem mass spectrometry analysis showed that all major milk proteins were present in all foulant streams. Proteins did appear to be the major cause of membrane fouling. Proteomics analysis of the foulants indicated elevated levels of serum proteins as compared with milk in the foulant fractions collected from the adsorption study. Caseins were preferentially introduced into the fouling layer during MF, when transmembrane pressure was applied, as confirmed both by proteomics and mineral analyses. The knowledge generated in this study advances the understanding of fouling mechanisms in cold MF of skim milk and can be used to identify solutions for minimizing membrane fouling and increasing the efficiency of milk MF. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Type XVII collagen (BP180) can function as a cell-matrix adhesion molecule via binding to laminin 332

PubMed Central

Van den Bergh, F.; Eliason, S.L.; Giudice, G.J.

2010-01-01

Collagen XVII (COL17) is a transmembrane glycoprotein that is expressed on the basal surface of basal epidermal keratinocytes. Previous observations have led to the hypothesis that an interaction between COL17 and laminin 332, an extracellular matrix protein, contributes to the attachment of the basal keratinocyte to the basement membrane. In order to isolate and manipulate COL17 interactions with ECM components, we induced COL17 expression in two cells lines, SK-MEL1 and K562, that exhibit little or no capacity to attach to our test substrates, including laminin 332, types I and IV collagen, and fibronectin. Cells expressing high levels of COL17 preferentially adhered to a laminin 332 matrix, and, to a lesser extent, type IV collagen, while showing little or no binding to type I collagen or fibronectin. A quantitative analysis of cell adhesive forces revealed that, compared with COL17-negative cells, COL17-positive cells required over 7-fold greater force to achieve 50% detachment from a laminin 332 substrate. When a cell preparation (either K562 or SK-MEL1) with heterogeneous COL17 expression levels was allowed to attach to a laminin 332 matrix, the COL17-positive and COL17-negative cells differentially sorted to the bound and unbound cell fractions, respectively. COL17-dependent attachment to laminin 332 could be reduced or abolished by siRNA-mediated knockdown of COL17 expression or by adding to the assay wells specific antibodies against COL17 or laminin 332. These findings provide strong support for the hypothesis that cell surface COL17 can interact with laminin 332 and, together, participate in the adherence of a cell to the extracellular matrix. PMID:21034821

Identification of an Extracellular Polysaccharide Network Essential for Cytochrome Anchoring and Biofilm Formation in Geobacter sulfurreducens▿ †

PubMed Central

Rollefson, Janet B.; Stephen, Camille S.; Tien, Ming; Bond, Daniel R.

2011-01-01

Transposon insertions in Geobacter sulfurreducens GSU1501, part of an ATP-dependent exporter within an operon of polysaccharide biosynthesis genes, were previously shown to eliminate insoluble Fe(III) reduction and use of an electrode as an electron acceptor. Replacement of GSU1501 with a kanamycin resistance cassette produced a similarly defective mutant, which could be partially complemented by expression of GSU1500 to GSU1505 in trans. The Δ1501 mutant demonstrated limited cell-cell agglutination, enhanced attachment to negatively charged surfaces, and poor attachment to positively charged poly-d-lysine- or Fe(III)-coated surfaces. Wild-type and mutant cells attached to graphite electrodes, but when electrodes were poised at an oxidizing potential inducing a positive surface charge (+0.24 V versus the standard hydrogen electrode [SHE]), Δ1501 mutant cells detached. Scanning electron microscopy revealed fibrils surrounding wild-type G. sulfurreducens which were absent from the Δ1501 mutant. Similar amounts of type IV pili and pilus-associated cytochromes were detected on both cell types, but shearing released a stable matrix of c-type cytochromes and other proteins bound to polysaccharides. The matrix from the mutant contained 60% less sugar and was nearly devoid of c-type cytochromes such as OmcZ. The addition of wild-type extracellular matrix to Δ1501 cultures restored agglutination and Fe(III) reduction. The polysaccharide binding dye Congo red preferentially bound wild-type cells and extracellular matrix material over mutant cells, and Congo red inhibited agglutination and Fe(III) reduction by wild-type cells. These results demonstrate a crucial role for the xap (extracellular anchoring polysaccharide) locus in metal oxide attachment, cell-cell agglutination, and localization of essential cytochromes beyond the Geobacter outer membrane. PMID:21169487

Fine particles on mars: Observations with the viking 1 lander cameras

USGS Publications Warehouse

Mutch, T.A.; Arvidson, R. E.; Binder, A.B.; Huck, F.O.; Levinthal, E.C.; Liebes, S.; Morris, E.C.; Nummedal, D.; Pollack, James B.; Sagan, C.

1976-01-01

Drifts of fine-grained sediment are present in the vicinity of the Viking 1 lander. Many drifts occur in the lees of large boulders. Morphologic analysis indicates that the last dynamic event was one of general deflation for at least some drifts. Particle cohesion implies that there is a distinct small-particle upturn in the threshold velocity-particle size curve; the apparent absence of the most easily moved particles (150 micrometers in diameter) may be due to their preferential transport to other regions or their preferential collisional destruction. A twilight rescan with lander cameras indicates a substantial amount of red dust with mean radius on the order of 1 micrometer in the atmosphere.

Fine particles on Mars: observations with the viking 1 lander cameras.

PubMed

Mutch, T A; Arvidson, R E; Binder, A B; Huck, F O; Levinthal, E C; Liebes, S; Morris, E C; Nummedal, D; Pollack, J B; Sagan, C

1976-10-01

Drifts of fine-grained sediment are present in the vicinity of the Viking 1 lander. Many drifts occur in the lees of large boulders. Morphologic analysis indicates that the last dynamic event was one of general deflation for at least some drifts. Particle cohesion implies that there is a distinct small-particle upturn in the threshold velocity-particle size curve; the apparent absence of the most easily moved particles (150 micrometers in diameter) may be due to their preferential transport to other regions or their preferential collisional destruction. A twilight rescan with lander cameras indicates a substantial amount of red dust with mean radius on the order of 1 micrometer in the atmosphere.

Unresolved trauma in mothers: intergenerational effects and the role of reorganization

PubMed Central

Iyengar, Udita; Kim, Sohye; Martinez, Sheila; Fonagy, Peter; Strathearn, Lane

2014-01-01

A mother's unresolved trauma may interfere with her ability to sensitively respond to her infant, thus affecting the development of attachment in her own child, and potentially contributing to the intergenerational transmission of trauma. One novel construct within the Dynamic Maturational Model of Attachment and Adaptation (DMM) coding of the Adult Attachment Interview (AAI) is “reorganization,” a process whereby speakers are actively changing their understanding of past and present experiences and moving toward attachment security. We conducted a study of mothers with unresolved trauma, exploring their own attachment classification, attachment outcomes of their children, and the potential effects of reorganization on child attachment. Forty-seven first-time mothers participated in the AAI during pregnancy, and returned with their child at 11 months to assess child attachment using the Strange Situation Procedure. Mothers with and without unresolved trauma were compared. We found that mothers with unresolved trauma had insecure attachment themselves and were more likely to have infants with insecure attachment. However, the one exception was that all of the mothers with unresolved trauma who were reorganizing toward secure attachment had infants with secure attachment. These preliminary findings suggest that mothers who are reorganizing may be able to more sensitively respond to their child's cues, contributing to the development of secure attachment. While our results need to be replicated in a larger cohort, this study is the first to explore the construct of reorganization and its potential relationship with child attachment. If confirmed in future studies, it may provide clinical insight into the intergenerational transmission of insecure attachment within the context of unresolved trauma. PMID:25225490

Escherichia coli attachment to model particulates: The effects of bacterial cell characteristics and particulate properties.

PubMed

Liang, Xiao; Liao, Chunyu; Soupir, Michelle L; Jarboe, Laura R; Thompson, Michael L; Dixon, Philip M

2017-01-01

E. coli bacteria move in streams freely in a planktonic state or attached to suspended particulates. Attachment is a dynamic process, and the fraction of attached microorganisms is thought to be affected by both bacterial characteristics and particulate properties. In this study, we investigated how the properties of cell surfaces and stream particulates influence attachment. Attachment assays were conducted for 77 E. coli strains and three model particulates (ferrihydrite, Ca-montmorillonite, or corn stover) under environmentally relevant conditions. Surface area, particle size distribution, and total carbon content were determined for each type of particulate. Among the three particulates, attachment fractions to corn stover were significantly larger than the attachments to 2-line ferrihydrite (p-value = 0.0036) and Ca-montmorillonite (p-value = 0.022). Furthermore, attachment to Ca-montmorillonite and corn stover was successfully modeled by a Generalized Additive Model (GAM) using cell characteristics as predictor variables. The natural logarithm of the net charge on the bacterial surface had a significant, positive, and linear impact on the attachment of E. coli bacteria to Ca-montmorillonite (p-value = 0.013), but it did not significantly impact the attachment to corn stover (p-value = 0.36). The large diversities in cell characteristics among 77 E. coli strains, particulate properties, and attachment fractions clearly demonstrated the inadequacy of using a static parameter or linear coefficient to predict the attachment behavior of E. coli in stream water quality models.

Anaerobic Dehalogenation of Chloroanilines by Dehalococcoides mccartyi Strain CBDB1 and Dehalobacter Strain 14DCB1 via Different Pathways as Related to Molecular Electronic Structure.

PubMed

Zhang, Shangwei; Wondrousch, Dominik; Cooper, Myriel; Zinder, Stephen H; Schüürmann, Gerrit; Adrian, Lorenz

2017-04-04

Dehalococcoides mccartyi strain CBDB1 and Dehalobacter strain 14DCB1 are organohalide-respiring microbes of the phyla Chloroflexi and Firmicutes, respectively. Here, we report the transformation of chloroanilines by these two bacterial strains via dissimilar dehalogenation pathways and discuss the underlying mechanism with quantum chemically calculated net atomic charges of the substrate Cl, H, and C atoms. Strain CBDB1 preferentially removed Cl doubly flanked by two Cl or by one Cl and NH 2 , whereas strain 14DCB1 preferentially dechlorinated Cl that has an ortho H. For the CBDB1-mediated dechlorination, comparative analysis with Hirshfeld charges shows that the least-negative Cl discriminates active from nonactive substrates in 14 out of 15 cases and may represent the preferred site of primary attack through cob(I)alamin. For the latter trend, three of seven active substrates provide strong evidence, with partial support from three of the remaining four substrates. Regarding strain 14DCB1, the most positive carbon-attached H atom discriminates active from nonactive chloroanilines in again 14 out of 15 cases. Here, regioselectivity is governed for 10 of the 11 active substrates by the most positive H attached to the highest-charge (most positive or least negative) aromatic C carrying the Cl to be removed. These findings suggest the aromatic ring H as primary site of attack through the supernucleophile Co(I), converting an initial H bond to a full electron transfer as start of the reductive dehalogenation. For both mechanisms, one- and two-electron transfer to Cl (strain CBDB1) or H (strain 14DCB1) are compatible with the presently available data. Computational chemistry research into reaction intermediates and pathways may further aid in understanding the bacterial reductive dehalogenation at the molecular level.

Preferential binding effects on protein structure and dynamics revealed by coarse-grained Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Pandey, R. B.; Jacobs, D. J.; Farmer, B. L.

2017-05-01

The effect of preferential binding of solute molecules within an aqueous solution on the structure and dynamics of the histone H3.1 protein is examined by a coarse-grained Monte Carlo simulation. The knowledge-based residue-residue and hydropathy-index-based residue-solvent interactions are used as input to analyze a number of local and global physical quantities as a function of the residue-solvent interaction strength (f). Results from simulations that treat the aqueous solution as a homogeneous effective solvent medium are compared to when positional fluctuations of the solute molecules are explicitly considered. While the radius of gyration (Rg) of the protein exhibits a non-monotonic dependence on solvent interaction over a wide range of f within an effective medium, an abrupt collapse in Rg occurs in a narrow range of f when solute molecules rapidly bind to a preferential set of sites on the protein. The structure factor S(q) of the protein with wave vector (q) becomes oscillatory in the collapsed state, which reflects segmental correlations caused by spatial fluctuations in solute-protein binding. Spatial fluctuations in solute binding also modify the effective dimension (D) of the protein in fibrous (D ˜ 1.3), random-coil (D ˜ 1.75), and globular (D ˜ 3) conformational ensembles as the interaction strength increases, which differ from an effective medium with respect to the magnitude of D and the length scale.

Molecular basis for polyol-induced protein stability revealed by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Liu, Fu-Feng; Ji, Luo; Zhang, Lin; Dong, Xiao-Yan; Sun, Yan

2010-06-01

Molecular dynamics simulations of chymotrypsin inhibitor 2 in different polyols (glycerol, xylitol, sorbitol, trehalose, and sucrose) at 363 K were performed to probe the molecular basis of the stabilizing effect, and the data in water, ethanol, and glycol were compared. It is found that protein protection by polyols is positively correlated with both the molecular volume and the fractional polar surface area, and the former contributes more significantly to the protein's stability. Polyol molecules have only a few direct hydrogen bonds with the protein, and the number of hydrogen bonds between a polyol and the protein is similar for different polyols. Thus, it is concluded that the direct interactions contribute little to the stabilizing effect. It is clarified that the preferential exclusion of the polyols is the origin of their protective effects, and it increases with increasing polyol size. Namely, there is preferential hydration on the protein surface (2 Å), and polyol molecules cluster around the protein at a distance of about 4 Å. The preferential exclusion of polyols leads to indirect interactions that prevent the protein from thermal unfolding. The water structure becomes more ordered with increasing the polyol size. So, the entropy of water in the first hydration shell decreases, and a larger extent of decrease is observed with increasing polyol size, leading to larger transfer free energy. The findings suggest that polyols protect the protein from thermal unfolding via indirect interactions. The work has thus elucidated the molecular mechanism of structural stability of the protein in polyol solutions.

Larval behavioral, morphological changes, and nematocyte dynamics during settlement of actinulae of Tubularia mesembryanthemum, Allman 1871 (Hydrozoa: Tubulariidae).

PubMed

Yamashita, Keiji; Kawaii, Satoru; Nakai, Mitsuyo; Fusetani, Nobuhiro

2003-06-01

The marine colonial hydroid Tubularia mesembryanthemum produces a morphologically unique dispersive stage, the actinula larva. Detailed observations were made on the behaviors and nematocyte dynamics of actinula larvae during attachment and morphogenesis by employing microscopic and time lapse video techniques. These observations produced four primary results. (1) Actinula larvae demonstrated two forms of attachment: temporary attachment by atrichous isorhiza (AI)-nematocysts discharged from the aboral tentacle (AT) tips-and permanent settlement by cement secretion from the columnar gland cells of the basal protrusion. (2) During larval settlement, numerous AIs were discharged from the AT tips with sinuous movement and rubbing of the tentacles onto the substrata, leading to "nematocyte-printing" around the settlement site. (3) Simultaneous with the discharge of the AIs, migration of stenoteles, desmonemes, and microbasic mastigophores occurred, resulting in a dramatic change of nematocyte composition in the ATs after larval settlement. This was in parallel with changes in larval behavior and the tentacle function. (4) Nematocyte-printing behavior during settlement could be recognized as metamorphic behavior responsible for irreversible changes in AT function, from attachment to feeding and defense.

Predicting the vibroacoustic response of satellite equipment panels.

PubMed

Conlon, S C; Hambric, S A

2003-03-01

Modern satellites are constructed of large, lightweight equipment panels that are strongly excited by acoustic pressures during launch. During design, performing vibroacoustic analyses to evaluate and ensure the integrity of the complex electronics mounted on the panels is critical. In this study the attached equipment is explicitly addressed and how its properties affect the panel responses is characterized. FEA and BEA methods are used to derive realistic parameters to input to a SEA hybrid model of a panel with multiple attachments. Specifically, conductance/modal density and radiation efficiency for nonhomogeneous panel structures with and without mass loading are computed. The validity of using the spatially averaged conductance of panels with irregular features for deriving the structure modal density is demonstrated. Maidanik's proposed method of modifying the traditional SEA input power is implemented, illustrating the importance of accounting for system internal couplings when calculating the external input power. The predictions using the SEA hybrid model agree with the measured data trends, and are found to be most sensitive to the assumed dynamic mass ratio (attachments/structure) and the attachment internal loss factor. Additional experimental and analytical investigations are recommended to better characterize dynamic masses, modal densities and loss factors.

Characterizing popularity dynamics of online videos

NASA Astrophysics Data System (ADS)

Ren, Zhuo-Ming; Shi, Yu-Qiang; Liao, Hao

2016-07-01

Online popularity has a major impact on videos, music, news and other contexts in online systems. Characterizing online popularity dynamics is nature to explain the observed properties in terms of the already acquired popularity of each individual. In this paper, we provide a quantitative, large scale, temporal analysis of the popularity dynamics in two online video-provided websites, namely MovieLens and Netflix. The two collected data sets contain over 100 million records and even span a decade. We characterize that the popularity dynamics of online videos evolve over time, and find that the dynamics of the online video popularity can be characterized by the burst behaviors, typically occurring in the early life span of a video, and later restricting to the classic preferential popularity increase mechanism.

Active Site Gate Dynamics Modulate the Catalytic Activity of the Ubiquitination Enzyme E2-25K.

PubMed

Rout, Manoj K; Lee, Brian L; Lin, Aiyang; Xiao, Wei; Spyracopoulos, Leo

2018-05-03

The ubiquitin proteasome system (UPS) signals for degradation of proteins through attachment of K48-linked polyubiquitin chains, or alterations in protein-protein recognition through attachment of K63-linked chains. Target proteins are ubiquitinated in three sequential chemical steps by a three-component enzyme system. Ubiquitination, or E2 enzymes, catalyze the central step by facilitating reaction of a target protein lysine with the C-terminus of Ub that is attached to the active site cysteine of the E2 through a thioester bond. E2 reactivity is modulated by dynamics of an active site gate, whose central residue packs against the active site cysteine in a closed conformation. Interestingly, for the E2 Ubc13, which specifically catalyzes K63-linked ubiquitination, the central gate residue adopts an open conformation. We set out to determine if active site gate dynamics play a role in catalysis for E2-25K, which adopts the canonical, closed gate conformation, and which selectively synthesizes K48-linked ubiquitin chains. Gate dynamics were characterized using mutagenesis of key residues, combined with enzyme kinetics measurements, and main chain NMR relaxation. The experimental data were interpreted with all atom MD simulations. The data indicate that active site gate opening and closing rates for E2-25K are precisely balanced.

Characterizing and modeling the dynamics of online popularity.

PubMed

Ratkiewicz, Jacob; Fortunato, Santo; Flammini, Alessandro; Menczer, Filippo; Vespignani, Alessandro

2010-10-08

Online popularity has an enormous impact on opinions, culture, policy, and profits. We provide a quantitative, large scale, temporal analysis of the dynamics of online content popularity in two massive model systems: the Wikipedia and an entire country's Web space. We find that the dynamics of popularity are characterized by bursts, displaying characteristic features of critical systems such as fat-tailed distributions of magnitude and interevent time. We propose a minimal model combining the classic preferential popularity increase mechanism with the occurrence of random popularity shifts due to exogenous factors. The model recovers the critical features observed in the empirical analysis of the systems analyzed here, highlighting the key factors needed in the description of popularity dynamics.

Wait Up!: Attachment and Sovereign Power

PubMed Central

Duschinsky, Robbie; Greco, Monica; Solomon, Judith

2017-01-01

Sociologists and feminist scholars have, over many decades, characterised attachment as a social construction that functions to support political and gender conservatism. We accept that attachment theory has seen use to these ends and consider recent deployments of attachment theory as justification for a minimal State within conservative political discourse in the UK since 2009. However, we contest that attachment is reducible to its discursive construction. We consider Judith Butler’s depiction of the infant attached to an abusive caregiver as a foundation and parallel to the position of the adult citizen subjected to punitive cultural norms and political institutions. We develop and qualify Butler’s account, drawing on the insights offered by the work of Lauren Berlant. We also return to Foucault’s Psychiatric Power lectures, in which familial relations are situated as an island of sovereign power within the sea of modern disciplinary institutions. These reflections help advance analysis of three important issues: the social and political implications of attachment research; the relationship between disciplinary and sovereign power in the affective dynamic of subjection; and the political and ethical status of professional activity within the psy disciplines. PMID:28904425

Interpersonal Processes and Attachment in Voice-Hearers.

PubMed

Robson, George; Mason, Oliver

2015-11-01

Studies of both clinical and non-clinical voice hearers suggest that distress is rather inconsistently associated with the perceived relationship between voice and hearer. It is also not clear if their beliefs about voices are relevant. This study investigated the links between attachment anxiety/avoidance, interpersonal aspects of the voice relationship, and distress whilst considering the impact of beliefs about voices and paranoia. Forty-four voice-hearing participants completed a number of self-report measures tapping attachment, interpersonal processes in the voice relationship, beliefs about voices, paranoia, distress and depression. Attachment avoidance was related to voice intrusiveness, hearer distance and distress. Attachment anxiety was related to voice intrusiveness, hearer dependence and distress. A series of simple mediation analyses were conducted that suggest that the relationship between attachment and voice related distress may be mediated by interpersonal dynamics in the voice-hearer relationship, beliefs about voices and paranoia. Beliefs about voices, the hearer's relationship with their voices, and the distress voices sometimes engender appear to be meaningfully related to their attachment style. This may be important to consider in therapeutic work.

Wait Up!: Attachment and Sovereign Power.

PubMed

Duschinsky, Robbie; Greco, Monica; Solomon, Judith

2015-09-01

Sociologists and feminist scholars have, over many decades, characterised attachment as a social construction that functions to support political and gender conservatism. We accept that attachment theory has seen use to these ends and consider recent deployments of attachment theory as justification for a minimal State within conservative political discourse in the UK since 2009. However, we contest that attachment is reducible to its discursive construction. We consider Judith Butler's depiction of the infant attached to an abusive caregiver as a foundation and parallel to the position of the adult citizen subjected to punitive cultural norms and political institutions. We develop and qualify Butler's account, drawing on the insights offered by the work of Lauren Berlant. We also return to Foucault's Psychiatric Power lectures, in which familial relations are situated as an island of sovereign power within the sea of modern disciplinary institutions. These reflections help advance analysis of three important issues: the social and political implications of attachment research; the relationship between disciplinary and sovereign power in the affective dynamic of subjection; and the political and ethical status of professional activity within the psy disciplines.

In vitro fibroblast and pre-osteoblastic cellular responses on laser surface modified Ti-6Al-4V.

PubMed

Chikarakara, Evans; Fitzpatrick, Patricia; Moore, Eric; Levingstone, Tanya; Grehan, Laura; Higginbotham, Clement; Vázquez, Mercedes; Bagga, Komal; Naher, Sumsun; Brabazon, Dermot

2014-12-29

The success of any implant, dental or orthopaedic, is driven by the interaction of implant material with the surrounding tissue. In this context, the nature of the implant surface plays a direct role in determining the long term stability as physico-chemical properties of the surface affect cellular attachment, expression of proteins, and finally osseointegration. Thus to enhance the degree of integration of the implant into the host tissue, various surface modification techniques are employed. In this work, laser surface melting of titanium alloy Ti-6Al-4V was carried out using a CO2 laser with an argon gas atmosphere. Investigations were carried out to study the influence of laser surface modification on the biocompatibility of Ti-6Al-4V alloy implant material. Surface roughness, microhardness, and phase development were recorded. Initial knowledge of these effects on biocompatibility was gained from examination of the response of fibroblast cell lines, which was followed by examination of the response of osteoblast cell lines which is relevant to the applications of this material in bone repair. Biocompatibility with these cell lines was analysed via Resazurin cell viability assay, DNA cell attachment assay, and alamarBlue metabolic activity assay. Laser treated surfaces were found to preferentially promote cell attachment, higher levels of proliferation, and enhanced bioactivity when compared to untreated control samples. These results demonstrate the tremendous potential of this laser surface melting treatment to significantly improve the biocompatibility of titanium implants in vivo.

Walking speed related joint kinetic alterations in trans-tibial amputees: impact of hydraulic 'ankle' damping.

PubMed

De Asha, Alan R; Munjal, Ramesh; Kulkarni, Jai; Buckley, John G

2013-10-17

Passive prosthetic devices are set up to provide optimal function at customary walking speed and thus may function less effectively at other speeds. This partly explains why joint kinetic adaptations become more apparent in lower-limb amputees when walking at speeds other than customary. The present study determined whether a trans-tibial prosthesis incorporating a dynamic-response foot that was attached to the shank via an articulating hydraulic device (hyA-F) lessened speed-related adaptations in joint kinetics compared to when the foot was attached via a rigid, non-articulating attachment (rigF). Eight active unilateral trans-tibial amputees completed walking trials at their customary walking speed, and at speeds they deemed to be slow-comfortable and fast-comfortable whilst using each type of foot attachment. Moments and powers at the distal end of the prosthetic shank and at the intact joints of both limbs were compared between attachment conditions. There was no change in the amount of intact-limb ankle work across speed or attachment conditions. As speed level increased there was an increase on both limbs in the amount of hip and knee joint work done, and increases on the prosthetic side were greater when using the hyA-F. However, because all walking speed levels were higher when using the hyA-F, the intact-limb ankle and combined joints work per meter travelled were significantly lower; particularly so at the customary speed level. This was the case despite the hyA-F dissipating more energy during stance. In addition, the amount of eccentric work done per meter travelled became increased at the residual knee when using the hyA-F, with increases again greatest at customary speed. Findings indicate that a trans-tibial prosthesis incorporating a dynamic-response foot reduced speed-related changes in compensatory intact-limb joint kinetics when the foot was attached via an articulating hydraulic device compared to rigid attachment. As differences between attachment conditions were greatest at customary speed, findings indicate a hydraulic ankle-foot device is most effectual at the speed it is set-up for.

Experimental and simulation-based investigation of He, Ne and Ar irradiation of polymers for ion microscopy

PubMed Central

Rzeznik, Lukasz; Fleming, Yves; Wirtz, Tom

2016-01-01

Summary Secondary ion mass spectrometry (SIMS) on the helium ion microscope (HIM) promises higher lateral resolution than on classical SIMS instruments. However, full advantage of this new technique can only be obtained when the interaction of He+ or Ne+ primary ions with the sample is fully controlled. In this work we investigate how He+ and Ne+ bombardment influences roughness formation and preferential sputtering for polymer samples and how they compare to Ar+ primary ions used in classical SIMS by combining experimental techniques with Molecular Dynamics (MD) simulations and SD_TRIM_SP modelling. The results show that diffusion coefficients for He, Ne and Ar in polymers are sufficiently high to prevent any accumulation of rare gas atoms in the polymers which could lead to some swelling and bubble formation. Roughness formation was also not observed. Preferential sputtering is more of a problem, with enrichment of carbon up to surface concentrations above 80%. In general, the preferential sputtering is largely depending on the primary ion species and the impact energies. For He+ bombardment, it is more of an issue for low keV impact energies and for the heavier primary ion species the preferential sputtering is sample dependent. For He+ steady state conditions are reached for fluences much higher than 1018 ions/cm2. For Ne+ and Ar+, the transient regime extends up to fluences of 1017–1018 ions/cm2. Hence, preferential sputtering needs to be taken into account when interpreting images recorded under He+ or Ne+ bombardment on the HIM. PMID:27547629

A novel model to assess lamellar signaling relevant to preferential weight bearing in the horse.

PubMed

Gardner, A K; van Eps, A W; Watts, M R; Burns, T A; Belknap, J K

2017-03-01

Supporting limb laminitis (SLL) is a devastating sequela to severe unilateral lameness in equine patients. The manifestation of SLL, which usually only affects one limb, is unpredictable and the etiology is unknown. A novel, non-painful preferential weight bearing model designed to mimic the effects of severe unilateral forelimb lameness was developed to assess lamellar signaling events in the supporting limb (SL). A custom v-shaped insert was attached to the shoe of one forelimb to prevent normal weight bearing and redistribute weight onto the SL. Testing of the insert using a custom scale platform built into the floor of stocks confirmed increased distribution of weight on the SL compared with the unloaded forelimb (UL) and the contralateral (CH) and ipsilateral (IH) hind limbs in six Standardbred horses. In a second part of the study, eight healthy Standardbred horses were fitted with the insert and tied with consistent monitoring and free access to hay and water for 48 h, after which the lamellae were harvested. Real-time qPCR was performed to assess lamellar mRNA concentrations of inflammatory genes and immunoblotting and immunofluorescence were performed to assess lamellar protein concentration and cellular localization of hypoxia-related proteins, respectively. Lamellar mRNA concentrations of inflammatory signaling proteins did not differ between SL and either CH or IH samples. HIF-1α concentrations were greater (P < 0.05) in the SL compared to the CH. This work establishes an experimental model to study preferential weight bearing and initial results suggest that lamellar hypoxia may occur in the SL. Copyright © 2017. Published by Elsevier Ltd.

Ultrafast dynamics of low-energy electron attachment via a non-valence correlation-bound state

NASA Astrophysics Data System (ADS)

Rogers, Joshua P.; Anstöter, Cate S.; Verlet, Jan R. R.

2018-03-01

The primary electron-attachment process in electron-driven chemistry represents one of the most fundamental chemical transformations with wide-ranging importance in science and technology. However, the mechanistic detail of the seemingly simple reaction of an electron and a neutral molecule to form an anion remains poorly understood, particularly at very low electron energies. Here, time-resolved photoelectron imaging was used to probe the electron-attachment process to a non-polar molecule using time-resolved methods. An initially populated diffuse non-valence state of the anion that is bound by correlation forces evolves coherently in ∼30 fs into a valence state of the anion. The extreme efficiency with which the correlation-bound state serves as a doorway state for low-energy electron attachment explains a number of electron-driven processes, such as anion formation in the interstellar medium and electron attachment to fullerenes.

Simulating Vibrations in a Complex Loaded Structure

NASA Technical Reports Server (NTRS)

Cao, Tim T.

2005-01-01

The Dynamic Response Computation (DIRECT) computer program simulates vibrations induced in a complex structure by applied dynamic loads. Developed to enable rapid analysis of launch- and landing- induced vibrations and stresses in a space shuttle, DIRECT also can be used to analyze dynamic responses of other structures - for example, the response of a building to an earthquake, or the response of an oil-drilling platform and attached tanks to large ocean waves. For a space-shuttle simulation, the required input to DIRECT includes mathematical models of the space shuttle and its payloads, and a set of forcing functions that simulates launch and landing loads. DIRECT can accommodate multiple levels of payload attachment and substructure as well as nonlinear dynamic responses of structural interfaces. DIRECT combines the shuttle and payload models into a single structural model, to which the forcing functions are then applied. The resulting equations of motion are reduced to an optimum set and decoupled into a unique format for simulating dynamics. During the simulation, maximum vibrations, loads, and stresses are monitored and recorded for subsequent analysis to identify structural deficiencies in the shuttle and/or payloads.

Atomic-Resolution X-ray Energy-Dispersive Spectroscopy Chemical Mapping of Substitutional Dy Atoms in a High-Coercivity Neodymium Magnet

NASA Astrophysics Data System (ADS)

Itakura, Masaru; Watanabe, Natsuki; Nishida, Minoru; Daio, Takeshi; Matsumura, Syo

2013-05-01

We have investigated local element distributions in a Dy-doped Nd2Fe14B hot-deformed magnet by atomic-column resolution chemical mapping using an X-ray energy-dispersive spectrometer (XEDS) attached to an aberration-corrected scanning transmission electron microscope (Cs-corrected STEM). The positions of the Nd and Dy atomic columns were visualized in the XEDS maps. The substitution of Dy was limited to a surface layer 2-3 unit cells thick in the Nd2Fe14B grains, and the Dy atoms preferentially occupied the 4f-Nd sites of Nd2Fe14B. These results provide further insights into the principal mechanism governing the coercivity enhancement due to Dy doping.

Zero Pearson coefficient for strongly correlated growing trees

NASA Astrophysics Data System (ADS)

Dorogovtsev, S. N.; Ferreira, A. L.; Goltsev, A. V.; Mendes, J. F. F.

2010-03-01

We obtained Pearson’s coefficient of strongly correlated recursive networks growing by preferential attachment of every new vertex by m edges. We found that the Pearson coefficient is exactly zero in the infinite network limit for the recursive trees (m=1) . If the number of connections of new vertices exceeds one (m>1) , then the Pearson coefficient in the infinite networks equals zero only when the degree distribution exponent γ does not exceed 4. We calculated the Pearson coefficient for finite networks and observed a slow power-law-like approach to an infinite network limit. Our findings indicate that Pearson’s coefficient strongly depends on size and details of networks, which makes this characteristic virtually useless for quantitative comparison of different networks.

Zero Pearson coefficient for strongly correlated growing trees.

PubMed

Dorogovtsev, S N; Ferreira, A L; Goltsev, A V; Mendes, J F F

2010-03-01

We obtained Pearson's coefficient of strongly correlated recursive networks growing by preferential attachment of every new vertex by m edges. We found that the Pearson coefficient is exactly zero in the infinite network limit for the recursive trees (m=1). If the number of connections of new vertices exceeds one (m>1), then the Pearson coefficient in the infinite networks equals zero only when the degree distribution exponent gamma does not exceed 4. We calculated the Pearson coefficient for finite networks and observed a slow power-law-like approach to an infinite network limit. Our findings indicate that Pearson's coefficient strongly depends on size and details of networks, which makes this characteristic virtually useless for quantitative comparison of different networks.

Caregivers' burden and depressive symptoms: the moderational role of attachment orientations.

PubMed

Vilchinsky, Noa; Dekel, Rachel; Revenson, Tracey A; Liberman, Gabriel; Mosseri, Morris

2015-03-01

The current study explored whether attachment orientations moderate the associations between caregiver burden and depressive symptoms among women coping with their partners' first time acute coronary syndrome. The association between burden and depression was hypothesized to be stronger among caregivers high on anxious attachment than among caregivers low on this dimension. In addition, the association between burden and depressive symptoms was hypothesized to be weaker among caregivers higher on avoidant attachment than among those lower on this dimension. The sample consisted of 111 female caregivers of male patients admitted to the cardiac care unit of a hospital in Israel. Caregivers completed a measure of attachment orientations during patients' hospitalization (baseline). Caregiver burden was measured 1 month later. Depressive symptoms were measured at baseline and again at 6-month follow-up. Structural equation modeling was used to test the moderational models. The association between caregiver burden and depressive symptoms at follow-up was moderated by attachment-related anxiety but not attachment-related avoidance. Congruent with predictions, a stronger association between caregiver burden and depressive symptoms occurred for caregivers with greater (vs. lower) attachment anxiety. The findings shed light on the possible dynamics among attachment orientations and affect regulation when coping with one's partner's illness. The findings are discussed in light of Pietromonaco, Uchino, and Dunkel Schetter's (2013) model of integrating attachment into health psychology research. PsycINFO Database Record (c) 2015 APA, all rights reserved.

Comprehension of Infrequent Subject-Verb Agreement Forms: Evidence from French-Learning Children

ERIC Educational Resources Information Center

Legendre, Geraldine; Barriere, Isabelle; Goyet, Louise; Nazzi, Thierry

2010-01-01

Two comprehension experiments were conducted to investigate whether young French-learning children (N = 76) are able to use a single number cue in subject-verb agreement contexts and match a visually dynamic scene with a corresponding verbal stimulus. Results from both preferential looking and pointing demonstrated significant comprehension in…

The influence of trehalose on hydrophobic interactions of small nonpolar solute: A molecular dynamics simulation study

NASA Astrophysics Data System (ADS)

Paul, Subrata; Paul, Sandip

2013-07-01

Molecular dynamics simulations were carried out to investigate the influences of aqueous trehalose solution on the hydrophobic interactions between neopentane molecules. In this study, we consider six different trehalose concentrations ranging from 0% to 56%. We observe that with increasing trehalose concentration the dispersion of solute neopentane takes place. The neopentane-neopentane association constant value decreases with addition of trehalose. Our preferential interaction calculations suggest that with increasing trehalose concentration neopentane interacts preferentially with water over trehalose. Site-site neopentane-trehalose rdfs indicate that trehalose molecules are expelled out from the neopentane surface. Also observed are (i) trehalose induced second shell collapse of water network (ii) decrease in average number of water-water and water-trehalose hydrogen bonds with increasing trehalose concentration. We also find that addition of trehalose decreases the translational motion of all the solution species. The decrease in diffusion coefficient value is more pronounced for trehalose. We, further, observe that the ratio of the diffusion coefficient values of water and trehalose increases with increasing trehalose concentration.

Preferential production and transport of grass-derived pyrogenic carbon in NE-Australian savanna ecosystems

NASA Astrophysics Data System (ADS)

Saiz, Gustavo; Goodrick, Iain; Wurster, Christopher; Nelson, Paul N.; Wynn, Jonathan; Bird, Michael

2017-12-01

Understanding the main factors driving fire regimes in grasslands and savannas is critical to better manage their biodiversity and functions. Moreover, improving our knowledge on pyrogenic carbon (PyC) dynamics, including formation, transport and deposition, is fundamental to better understand a significant slow-cycling component of the global carbon cycle, particularly as these ecosystems account for a substantial proportion of the area globally burnt. However, a thorough assessment of past fire regimes in grass-dominated ecosystems is problematic due to challenges in interpreting the charcoal record of sediments. It is therefore critical to adopt appropriate sampling and analytical methods to allow the acquisition of reliable data and information on savanna fire dynamics. This study uses hydrogen pyrolysis (HyPy) to quantify PyC abundance and stable isotope composition (δ13C) in recent sediments across 38 micro-catchments covering a wide range of mixed C3/C4 vegetation in north Queensland, Australia. We exploited the contrasting δ13C values of grasses (i.e. C4; δ13C >-15‰) and woody vegetation (i.e. C3; δ13C <-24‰) to assess the preferential production and transport of grass-derived PyC in savanna ecosystems. Analyses were conducted on bulk and size-fractionated samples to determine the fractions into which PyC preferentially accumulates. Our data show that the δ13C value of PyC in the sediments is decoupled from the δ13C value of total organic carbon, which suggests that a significant component of PyC may be derived from incomplete grass combustion, even when the proportion of C4 grass biomass in the catchment was relatively small. Furthermore, we conducted 16 experimental burns that indicate that there is a comminution of PyC produced in-situ to smaller particles, which facilitates the transport of this material, potentially affecting its preservation potential. Savanna fires preferentially burn the grass understory rather than large trees, leading to a bias toward the finer C4–derived PyC in the sedimentary record. This in turn, provides further evidence for the preferential production and transport of C4-derived PyC in mixed ecosystems where grass and woody vegetation coexist. Moreover, our isotopic approach provides independent validation of findings derived from conventional charcoal counting techniques concerning the appropriateness of adopting a relatively small particle size threshold.

Conservation of Matrix Attachment Region-Binding Filament-Like Protein 1 among Higher Plants1

PubMed Central

Harder, Patricia A.; Silverstein, Rebecca A.; Meier, Iris

2000-01-01

The interaction of chromatin with the nuclear matrix via matrix attachment regions (MARs) on the DNA is considered to be of fundamental importance for higher-order chromatin organization and the regulation of gene expression. We have previously isolated a novel nuclear matrix-localized protein (MFP1) from tomato (Lycopersicon esculentum) that preferentially binds to MAR DNA. Tomato MFP1 has a predicted filament-protein-like structure and is associated with the nuclear envelope via an N-terminal targeting domain. Based on the antigenic relationship, we report here that MFP1 is conserved in a large number of dicot and monocot species. Several cDNAs were cloned from tobacco (Nicotiana tabacum) and shown to correspond to two tobacco MFP1 genes. Comparison of the primary and predicted secondary structures of MFP1 from tomato, tobacco, and Arabidopsis indicates a high degree of conservation of the N-terminal targeting domain, the overall putative coiled-coil structure of the protein, and the C-terminal DNA-binding domain. In addition, we show that tobacco MFP1 is regulated in an organ-specific and developmental fashion, and that this regulation occurs at the level of transcription or RNA stability. PMID:10631266

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

Robert Radtke

The manufacture of thermally stable diamond (TSP) cutters for drill bits used in petroleum drilling requires the brazing of two dissimilar materials--TSP diamond and tungsten carbide. The ENDURUS{trademark} thermally stable diamond cutter developed by Technology International, Inc. exhibits (1) high attachment (shear) strength, exceeding 345 MPa (50,000 psi), (2) TSP diamond impact strength increased by 36%, (3) prevents TSP fracture when drilling hard rock, and (4) maintains a sharp edge when drilling hard and abrasive rock. A novel microwave brazing (MWB) method for joining dissimilar materials has been developed. A conventional braze filler metal is combined with microwave heating whichmore » minimizes thermal residual stress between materials with dissimilar coefficients of thermal expansion. The process results in preferential heating of the lower thermal expansion diamond material, thus providing the ability to match the thermal expansion of the dissimilar material pair. Methods for brazing with both conventional and exothermic braze filler metals have been developed. Finite element modeling (FEM) assisted in the fabrication of TSP cutters controllable thermal residual stress and high shear attachment strength. Further, a unique cutter design for absorbing shock, the densification of otherwise porous TSP diamond for increased mechanical strength, and diamond ion implantation for increased diamond fracture resistance resulted in successful drill bit tests.« less

Software tools for data modelling and processing of human body temperature circadian dynamics.

PubMed

Petrova, Elena S; Afanasova, Anastasia I

2015-01-01

This paper is presenting a software development for simulating and processing thermometry data. The motivation of this research is the miniaturization of actuators attached to human body which allow frequent temperature measurements and improve the medical diagnosis procedures related to circadian dynamics.

One- and Two-Color Resonant Photoionization Spectroscopy of Chromium-Doped Helium Nanodroplets

PubMed Central

2014-01-01

We investigate the photoinduced relaxation dynamics of Cr atoms embedded into superfluid helium nanodroplets. One- and two-color resonant two-photon ionization (1CR2PI and 2CR2PI, respectively) are applied to study the two strong ground state transitions z7P2,3,4° ← a7S3 and y7P2,3,4° ← a7S3. Upon photoexcitation, Cr* atoms are ejected from the droplet in various excited states, as well as paired with helium atoms as Cr*–Hen exciplexes. For the y7P2,3,4° intermediate state, comparison of the two methods reveals that energetically lower states than previously identified are also populated. With 1CR2PI we find that the population of ejected z5P3° states is reduced for increasing droplet size, indicating that population is transferred preferentially to lower states during longer interaction with the droplet. In the 2CR2PI spectra we find evidence for generation of bare Cr atoms in their septet ground state (a7S3) and metastable quintet state (a5S2), which we attribute to a photoinduced fast excitation–relaxation cycle mediated by the droplet. A fraction of Cr atoms in these ground and metastable states is attached to helium atoms, as indicated by blue wings next to bare atom spectral lines. These relaxation channels provide new insight into the interaction of excited transition metal atoms with helium nanodroplets. PMID:24708058

Experience versus talent shapes the structure of the Web.

PubMed

Kong, Joseph S; Sarshar, Nima; Roychowdhury, Vwani P

2008-09-16

We use sequential large-scale crawl data to empirically investigate and validate the dynamics that underlie the evolution of the structure of the web. We find that the overall structure of the web is defined by an intricate interplay between experience or entitlement of the pages (as measured by the number of inbound hyperlinks a page already has), inherent talent or fitness of the pages (as measured by the likelihood that someone visiting the page would give a hyperlink to it), and the continual high rates of birth and death of pages on the web. We find that the web is conservative in judging talent and the overall fitness distribution is exponential, showing low variability. The small variance in talent, however, is enough to lead to experience distributions with high variance: The preferential attachment mechanism amplifies these small biases and leads to heavy-tailed power-law (PL) inbound degree distributions over all pages, as well as over pages that are of the same age. The balancing act between experience and talent on the web allows newly introduced pages with novel and interesting content to grow quickly and surpass older pages. In this regard, it is much like what we observe in high-mobility and meritocratic societies: People with entitlement continue to have access to the best resources, but there is just enough screening for fitness that allows for talented winners to emerge and join the ranks of the leaders. Finally, we show that the fitness estimates have potential practical applications in ranking query results.

Evolution of the social network of scientific collaborations

NASA Astrophysics Data System (ADS)

Barabási, A. L.; Jeong, H.; Néda, Z.; Ravasz, E.; Schubert, A.; Vicsek, T.

2002-08-01

The co-authorship network of scientists represents a prototype of complex evolving networks. In addition, it offers one of the most extensive database to date on social networks. By mapping the electronic database containing all relevant journals in mathematics and neuro-science for an 8-year period (1991-98), we infer the dynamic and the structural mechanisms that govern the evolution and topology of this complex system. Three complementary approaches allow us to obtain a detailed characterization. First, empirical measurements allow us to uncover the topological measures that characterize the network at a given moment, as well as the time evolution of these quantities. The results indicate that the network is scale-free, and that the network evolution is governed by preferential attachment, affecting both internal and external links. However, in contrast with most model predictions the average degree increases in time, and the node separation decreases. Second, we propose a simple model that captures the network's time evolution. In some limits the model can be solved analytically, predicting a two-regime scaling in agreement with the measurements. Third, numerical simulations are used to uncover the behavior of quantities that could not be predicted analytically. The combined numerical and analytical results underline the important role internal links play in determining the observed scaling behavior and network topology. The results and methodologies developed in the context of the co-authorship network could be useful for a systematic study of other complex evolving networks as well, such as the world wide web, Internet, or other social networks.

Dynamic contact guidance of migrating cells

NASA Astrophysics Data System (ADS)

Losert, Wolfgang; Sun, Xiaoyu; Guven, Can; Driscoll, Meghan; Fourkas, John

2014-03-01

We investigate the effects of nanotopographical surfaces on the cell migration and cell shape dynamics of the amoeba Dictyostelium discoideum. Amoeboid motion exhibits significant contact guidance along surfaces with nanoscale ridges or grooves. We show quantitatively that nanoridges spaced 1.5 μm apart exhibit the greatest contact guidance efficiency. Using principal component analysis, we characterize the dynamics of the cell shape modulated by the coupling between the cell membrane and ridges. We show that motion parallel to the ridges is enhanced, while the turning, at the largest spatial scales, is suppressed. Since protrusion dynamics are principally governed by actin dynamics, we imaged the actin polymerization of cells on ridges. We found that actin polymerization occurs preferentially along nanoridges in a ``monorail'' like fashion. The ridges then provide us with a tool to study actin dynamics in an effectively reduced dimensional system.

Dynamics of Flagellum- and Pilus-Mediated Association of Pseudomonas aeruginosa with Contact Lens Surfaces▿

PubMed Central

Tran, Victoria B.; Fleiszig, Suzanne M. J.; Evans, David J.; Radke, Clayton J.

2011-01-01

Flagella and pili are appendages that modulate attachment of Pseudomonas aeruginosa to solid surfaces. However, previous studies have mostly reported absolute attachment. Neither the dynamic roles of these appendages in surface association nor those of attachment phenotypes have been quantified. We used video microscopy to address this issue. Unworn, sterile, soft contact lenses were placed in a laminar-flow optical chamber. Initial lens association kinetics for P. aeruginosa strain PAK were assessed in addition to lens-surface association phenotypes. Comparisons were made to strains with mutations in flagellin (fliC) or pilin (pilA) or those in flagellum (motAB) or pilus (pilU) function. PAK and its mutants associated with the contact lens surface at a constant rate according to first-order kinetics. Nonswimming mutants associated ∼30 to 40 times slower than the wild type. PAK and its pilA mutant associated at similar rates, but each ∼4 times faster than the pilU mutant. Lens attachment by wild-type PAK induced multiple phenotypes (static, lateral, and rotational surface movement), each showing only minor detachment. Flagellin (fliC) and flagellar-motility (motAB) mutants did not exhibit surface rotation. Conversely, strains with mutations in pilin (pilA) and pilus retraction (pilU) lacked lateral-surface movement but displayed enhanced surface rotation. Slower surface association of swimming-incapable P. aeruginosa mutants was ascribed to lower convective-diffusion-arrival rates, not to an inability to adhere. Flagellum function (swimming) enhanced lens association, attachment, and rotation; hyperpiliation hindered lens association. P. aeruginosa bound through three different adhesion sites: flagellum, pili, and body. Reduction of bacterial attachment to contact lenses thus requires blockage of multiple adhesion phenotypes. PMID:21498762

Attachment and Jealousy: Understanding the Dynamic Experience of Jealousy Using the Response Escalation Paradigm.

PubMed

Huelsnitz, Chloe O; Farrell, Allison K; Simpson, Jeffry A; Griskevicius, Vladas; Szepsenwol, Ohad

2018-04-01

Jealousy is a complex, dynamic experience that unfolds over time in relationship-threatening situations. Prior research has used retrospective reports that cannot disentangle initial levels and change in jealousy in response to escalating threat. In three studies, we examined responses to the Response Escalation Paradigm (REP)-a 5-stage hypothetical scenario in which individuals are exposed to increasing levels of relationship threat-as a function of attachment orientations. Highly anxious individuals exhibited hypervigilant, slow escalation response patterns, interfered earlier in the REP, felt more jealousy, sadness, and worry when they interfered, and wanted to engage in more vigilant, destructive, and passive behaviors aimed at their partner. Highly avoidant individuals felt more anger when they interfered in the REP and wanted to engage in more partner-focused, destructive behaviors. The REP offers a dynamic method for inducing and examining jealousy and introduces a novel approach to studying other emotional experiences.

Maintenance of a functional higher order chromatin structure: The role of the nuclear matrix in normal and disease states

PubMed Central

Linnemann, Amelia K.; Krawetz, Stephen A.

2010-01-01

Summary The ordered packaging of DNA within the nucleus of somatic cells reflects a dynamic supportive structure that facilitates stable transcription interrupted by intermittent cycles of extreme condensation. This dynamic mode of packing and unpacking chromatin is intimately linked to the ability of the genome to specifically complex with both histones and non-histone proteins. Understanding the underlying mechanism that governs the formation of higher order chromatin structures is a key to understanding how local architecture modulates transcription. In part, the formation of these structures appears to be regulated through genomic looping that is dynamically mediated by attachment to the nuclear scaffold/matrix at S/MARs, i.e., Scaffold/Matrix Attachment Regions. Although the mechanism guiding the formation and use of these higher-ordered structures remains unknown, S/MARs continue to reveal a multitude of roles in development and the pathogenesis of disease. PMID:20948980

Maintenance of a functional higher order chromatin structure: The role of the nuclear matrix in normal and disease states.

PubMed

Linnemann, Amelia K; Krawetz, Stephen A

2009-01-01

The ordered packaging of DNA within the nucleus of somatic cells reflects a dynamic supportive structure that facilitates stable transcription interrupted by intermittent cycles of extreme condensation. This dynamic mode of packing and unpacking chromatin is intimately linked to the ability of the genome to specifically complex with both histones and non-histone proteins. Understanding the underlying mechanism that governs the formation of higher order chromatin structures is a key to understanding how local architecture modulates transcription. In part, the formation of these structures appears to be regulated through genomic looping that is dynamically mediated by attachment to the nuclear scaffold/matrix at S/MARs, i.e., Scaffold/Matrix Attachment Regions. Although the mechanism guiding the formation and use of these higher-ordered structures remains unknown, S/MARs continue to reveal a multitude of roles in development and the pathogenesis of disease.

Linking soil moisture balance and source-responsive models to estimate diffuse and preferential components of groundwater recharge

USGS Publications Warehouse

Cuthbert, M.O.; Mackay, R.; Nimmo, J.R.

2012-01-01

Results are presented of a detailed study into the vadose zone and shallow water table hydrodynamics of a field site in Shropshire, UK. A conceptual model is developed and tested using a range of numerical models, including a modified soil moisture balance model (SMBM) for estimating groundwater recharge in the presence of both diffuse and preferential flow components. Tensiometry reveals that the loamy sand topsoil wets up via macropore flow and subsequent redistribution of moisture into the soil matrix. Recharge does not occur until near-positive pressures are achieved at the top of the sandy glaciofluvial outwash material that underlies the topsoil, about 1 m above the water table. Once this occurs, very rapid water table rises follow. This threshold behaviour is attributed to the vertical discontinuity in the macropore system due to seasonal ploughing of the topsoil, and a lower permeability plough/iron pan restricting matrix flow between the topsoil and the lower outwash deposits. Although the wetting process in the topsoil is complex, a SMBM is shown to be effective in predicting the initiation of preferential flow from the base of the topsoil into the lower outwash horizon. The rapidity of the response at the water table and a water table rise during the summer period while flow gradients in the unsaturated profile were upward suggest that preferential flow is also occurring within the outwash deposits below the topsoil. A variation of the source-responsive model proposed by Nimmo (2010) is shown to reproduce the observed water table dynamics well in the lower outwash horizon when linked to a SMBM that quantifies the potential recharge from the topsoil. The results reveal new insights into preferential flow processes in cultivated soils and provide a useful and practical approach to accounting for preferential flow in studies of groundwater recharge estimation.

Stokes Approach to Preferential Flow at the Darcy-Scale

NASA Astrophysics Data System (ADS)

Germann, Peter; Bogner, Christina

2017-04-01

Preferential Flow in soils is fast, limited to infiltration and occupies but a small portion of porosity. However, how fast is it, how much water is involved, what is its flow rate, and how far is it carried? Supported with numerous measurements a Stokes approach to preferential flow provides the answers at the operational Darcy-scale. The approach to preferential flow in permeable media (pm) stresses momentum dissipation during viscous flow. Thus, a laminar water film percolates through a pm. The dynamic film is initially determined by the thickness F (m) and the specific contact area L (m2 m-3) per unit volume of the medium. Input to the medium's surface is a pulse with volume flux density q (ms-1) that starts and ends at times TB and TE. A specific pulse and the intrinsic properties of a pm determine F and L. A water content wave (WCW) envelops the spatio-temporal evolution of a water film. A WCW is completely described with a set of analytical relationships that are based on F, L, and the water's viscosity. The approach is an extension of Hagen-Poiseuille's law of flow in concentric conduits. It also evolves seamlessly from extending Darcy's law into non-saturated pm. Experimental determination of F and L follows either from drainage flow or from rapid soil moisture recordings during the passing of a WCW, for instance, with TDR-equipment. Parameters from numerous infiltration experiments in the field, in soil columns, in sand boxes, and lysimeters demonstrate the approach's broad applicability, thus framing the spatio-temporal extensions, velocities and volume flux densities of preferential flows. The specific contact area L is considered the locus of water, heat, particle and solute transfer between a WCW and the sessile parts of a pm. A recent analysis of delayed Br-breakthrough with respect to drainage flow supports the feasibility of the Stokes approach to preferential flow at the Darcy-scale. A perspective of modeling sequences of input pulses will conclude the presentation.

Impacts Assessment of Dynamic Speed Harmonization with Queue Warning : Task 3, Impacts Assessment Report. [supporting datasets

DOT National Transportation Integrated Search

2015-05-31

The datasets in the .pdf and .zip attached to this record are in support of Intelligent Transportation Systems Joint Program Office (ITS JPO) report FHWA-JPO-15-222, "Impacts Assessment of Dynamic Speed Harmonization with Queue Warning : Task 3, Impa...

Computing Dynamics Of A Robot Of 6+n Degrees Of Freedom

NASA Technical Reports Server (NTRS)

Quiocho, Leslie J.; Bailey, Robert W.

1995-01-01

Improved formulation speeds and simplifies computation of dynamics of robot arm of n rotational degrees of freedom mounted on platform having three translational and three rotational degrees of freedom. Intended for use in dynamical modeling of robotic manipulators attached to such moving bases as spacecraft, aircraft, vessel, or land vehicle. Such modeling important part of simulation and control of robotic motions.

Attachment, parenting styles and bullying during pubertal years.

PubMed

van der Watt, Ronél

2014-01-01

Research that focuses on combining attachment, parenting styles, bullying and the reciprocal nature thereof in the parent-adolescent and peer relationships is limited. The bio-psychosocial changes that adolescents experience open up broader social realities and are perceived differently by parents and adolescents. Attachment processes and parenting styles may elicit dissimilar perceptions. These processes are also associated with the multifaceted dynamics of bullying. The aim of the article is to advocate for research on the possible link between the implications of attachment, parenting styles and bullying. Exploring the association between attachment, parenting styles and bullying can deepen the understanding of the developmental challenges within the parent-adolescent relationship, add insight to the different perceptions of adolescents and parents, and complement intervention programmes accordingly. Firstly, this article outlines bio-psychosocial changes in the pubertal years as related to the social realities of the adolescent. Secondly, a discussion on the concepts 'attachment', 'parenting styles', 'bullying', and the potential link between these concepts will follow. Thirdly, an outline of the clinical implications of the apparent association between these concepts is given. The article concludes with recommendations that researchers can consider while exploring the relationship between attachment, parenting styles, and bullying and the delineation thereof in the parent-adolescent relationship.

The Impact of Heterogeneity on Threshold-Limited Social Contagion, and on Crowd Decision-Making

NASA Astrophysics Data System (ADS)

Karampourniotis, Panagiotis Dimitrios

Recent global events and their poor predictability are often attributed to the complexity of the world event dynamics. A key factor generating the turbulence is human diversity. Here, we study the impact of heterogeneity of individuals on opinion formation and emergence of global biases. In the case of opinion formation, we focus on the heterogeneity of individuals' susceptibility to new ideas. In the case of global biases, we focus on the aggregated heterogeneity of individuals in a country. First, to capture the complex nature of social influencing we use a simple but classic model of contagion spreading in complex social systems, namely the threshold model. We investigate numerically and analytically the transition in the behavior of threshold-limited cascades in the presence of multiple initiators as the distribution of thresholds is varied between the two extreme cases of identical thresholds and a uniform distribution. We show that individuals' heterogeneity of susceptibility governs the dynamics, resulting in different sizes of initiators needed for consensus. Furthermore, given the impact of heterogeneity on the cascade dynamics, we investigate selection strategies for accelerating consensus. To this end, we introduce two new selection strategies for Influence Maximization. One of them focuses on finding the balance between targeting nodes which have high resistance to adoptions versus nodes positioned in central spots in networks. The second strategy focuses on the combination of nodes for reaching consensus, by targeting nodes which increase the group's influence. Our strategies outperform other existing strategies regardless of the susceptibility diversity and network degree assortativity. Finally, we study the aggregated biases of humans in a global setting. The emergence of technology and globalization gives raise to the debate on whether the world moves towards becoming flat, a world where preferential attachment does not govern economic growth. By studying the data from a global lending platform we discover that geographical proximity and cultural affinity are highly negatively correlated with levels of flatness of the world. Furthermore, we investigate the robustness of the flatness of the world against sudden catastrophic national events such as political disruptions, by removing countries (nodes) or connections (edges) between them.

Hybrid ZnPc@TiO2 nanostructures for targeted photodynamic therapy, bioimaging and doxorubicin delivery.

PubMed

Flak, Dorota; Yate, Luis; Nowaczyk, Grzegorz; Jurga, Stefan

2017-09-01

In this study ZnPc@TiO 2 hybrid nanostructures, both nanoparticles and nanotubes, as potential photosensitizers for the photodynamic therapy, fluorescent bioimaging agents, as well as anti-cancer drug nanocarriers, were prepared via zinc phthalocyanine (ZnPc) deposition on TiO 2 . In order to provide the selectivity of prepared hybrid nanostructures towards cancer cells they were modified with folic acid molecules (FA). The efficient attachment of both ZnPc and FA molecules was confirmed with dynamic light scattering (DLS), zeta potential measurements and X-ray photoelectron spectroscopy (XPS). It was presented that ZnPc and FA attachment has a strong effect on fluorescence emission properties of TiO 2 nanostructures, which can be further used for their simultaneous visualization upon cellular uptake. ZnPc@TiO 2 and FA/ZnPc@TiO 2 hybrid nanotubes were then employed as doxorubicin nanocarriers. It was demonstrated that doxorubicin can be easily loaded on these hybrid nanostructures via an electrostatic interaction and then released. In vitro cytotoxicity and photo-cytotoxic activity studies showed that prepared hybrid nanostructures were selectively targeting to cancer cells. Doxorubicin loaded hybrid nanostructures were significantly more cytotoxic than un-loaded ones and their cytotoxic effect was even more severe upon irradiation. The cellular uptake of prepared hybrid nanostructures and their localization in cells was monitored in vitro in 2D cell culture and tumor-like 3D multicellular culture environment with fluorescent confocal microscopy. These hybrid nanostructures preferentially penetrated into human cervical cancer cells (HeLa) than into normal fibroblasts (MSU-1.1) and were mainly localized within the cell cytoplasm. HeLa cells spheroids were also efficiently labelled by prepared hybrid nanostructures. Fluorescent imaging of Hela cells treated with doxorubicin loaded hybrid nanostructures showed that doxorubicin was effectively delivered into cells, released and evenly distributed in the cytoplasm. In conclusion, prepared hybrid nanostructures exhibit high potential as selective bioimaging agents next to their photodynamic activity and drug delivery ability. Copyright © 2017 Elsevier B.V. All rights reserved.

Laboratory-based observations of capillary barriers and preferential flow in layered snow

NASA Astrophysics Data System (ADS)

Avanzi, F.; Hirashima, H.; Yamaguchi, S.; Katsushima, T.; De Michele, C.

2015-12-01

Several evidences are nowadays available that show how the effects of capillary gradients and preferential flow on water transmission in snow may play a more important role than expected. To observe these processes and to contribute in their characterization, we performed observations on the development of capillary barriers and preferential flow patterns in layered snow during cold laboratory experiments. We considered three different layering (all characterized by a finer-over-coarser texture in grain size) and three different water input rates. Nine samples of layered snow were sieved in a cold laboratory, and subjected to a constant supply of dyed tracer. By means of visual inspection, horizontal sectioning and liquid water content measurements, the processes of ponding and preferential flow were characterized as a function of texture and water input rate. The dynamics of each sample were replicated using the multi-layer physically-based SNOWPACK model. Results show that capillary barriers and preferential flow are relevant processes ruling the speed of liquid water in stratified snow. Ponding is associated with peaks in LWC at the boundary between the two layers equal to ~ 33-36 vol. % when the upper layer is composed by fine snow (grain size smaller than 0.5 mm). The thickness of the ponding layer at the textural boundary is between 0 and 3 cm, depending on sample stratigraphy. Heterogeneity in water transmission increases with grain size, while we do not observe any clear dependency on water input rate. The extensive comparison between observed and simulated LWC profiles by SNOWPACK (using an approximation of Richards Equation) shows high performances by the model in estimating the LWC peak over the boundary, while water speed in snow is underestimated by the chosen water transport scheme.

Stronger Neural Dynamics Capture Changes in Infants' Visual Working Memory Capacity over Development

ERIC Educational Resources Information Center

Perone, Sammy; Simmering, Vanessa R.; Spencer, John P.

2011-01-01

Visual working memory (VWM) capacity has been studied extensively in adults, and methodological advances have enabled researchers to probe capacity limits in infancy using a preferential looking paradigm. Evidence suggests that capacity increases rapidly between 6 and 10 months of age. To understand how the VWM system develops, we must understand…

Assessing attachment in school-aged children: Do the School-Age Assessment of Attachment and Family Drawings work together as complementary tools?

PubMed

Carr-Hopkins, Rebecca; De Burca, Calem; Aldridge, Felicity A

2017-07-01

Our goal was to identify an assessment package that could improve treatment planning for troubled children and their families. To assess the validity of our tools, we tested the relations among the School-Age Assessment of Attachment, the Family Drawing and children's risk status. We used the Dynamic-Maturational Model of Attachment and Adaptation to interpret the assessments in the hope of identifying a gradient of risk, and explore whether a new coding method improved the validity of Family Drawings and their utility as a tool to complement the School-Age Assessment of Attachment. The participants were 89 children, aged between 5 and 12 years; 32 children were involved with mental health services or child protection. Each child completed a School-Age Assessment of Attachment and a Family Drawing. Both assessments differentiated between clinical and normative referrals with moderate effect sizes when dichotomizing risk versus non-risk attachment. When the analysis incorporated a gradient of six attachment classifications, the effect sizes decreased, but specificity of risk increased. The School-Age Assessment of Attachment had greater validity for discriminating risk, and type of risk, than the Family Drawings. With a School-Age Assessment of Attachment and family history, the Family Drawing can provide information about distress that some children do not provide verbally. Integration of the two assessment tools alongside information about parental and family functioning appears to be the key to formulating children's problems.

Covalent dye attachment influences the dynamics and conformational properties of flexible peptides

PubMed Central

Crevenna, Alvaro H.; Bomblies, Rainer; Lamb, Don C.

2017-01-01

Fluorescence spectroscopy techniques like Förster resonance energy transfer (FRET) and fluorescence correlation spectroscopy (FCS) have become important tools for the in vitro and in vivo investigation of conformational dynamics in biomolecules. These methods rely on the distance-dependent quenching of the fluorescence signal of a donor fluorophore either by a fluorescent acceptor fluorophore (FRET) or a non-fluorescent quencher, as used in FCS with photoinduced electron transfer (PET). The attachment of fluorophores to the molecule of interest can potentially alter the molecular properties and may affect the relevant conformational states and dynamics especially of flexible biomolecules like intrinsically disordered proteins (IDP). Using the intrinsically disordered S-peptide as a model system, we investigate the impact of terminal fluorescence labeling on the molecular properties. We perform extensive molecular dynamics simulations on the labeled and unlabeled peptide and compare the results with in vitro PET-FCS measurements. Experimental and simulated timescales of end-to-end fluctuations were found in excellent agreement. Comparison between simulations with and without labels reveal that the π-stacking interaction between the fluorophore labels traps the conformation of S-peptide in a single dominant state, while the unlabeled peptide undergoes continuous conformational rearrangements. Furthermore, we find that the open to closed transition rate of S-peptide is decreased by at least one order of magnitude by the fluorophore attachment. Our approach combining experimental and in silico methods provides a benchmark for the simulations and reveals the significant effect that fluorescence labeling can have on the conformational dynamics of small biomolecules, at least for inherently flexible short peptides. The presented protocol is not only useful for comparing PET-FCS experiments with simulation results but provides a strategy to minimize the influence on molecular properties when chosing labeling positions for fluorescence experiments. PMID:28542243

Meiotic recombination modulates the structure and dynamics of the synaptonemal complex during C. elegans meiosis

PubMed Central

2017-01-01

During meiotic prophase, a structure called the synaptonemal complex (SC) assembles at the interface between aligned pairs of homologous chromosomes, and crossover recombination events occur between their DNA molecules. Here we investigate the inter-relationships between these two hallmark features of the meiotic program in the nematode C. elegans, revealing dynamic properties of the SC that are modulated by recombination. We demonstrate that the SC incorporates new subunits and switches from a more highly dynamic/labile state to a more stable state as germ cells progress through the pachytene stage of meiotic prophase. We further show that the more dynamic state of the SC is prolonged in mutants where meiotic recombination is impaired. Moreover, in meiotic mutants where recombination intermediates are present in limiting numbers, SC central region subunits become preferentially stabilized on the subset of chromosome pairs that harbor a site where pro-crossover factors COSA-1 and MutSγ are concentrated. Polo-like kinase PLK-2 becomes preferentially localized to the SCs of chromosome pairs harboring recombination sites prior to the enrichment of SC central region proteins on such chromosomes, and PLK-2 is required for this enrichment to occur. Further, late pachytene nuclei in a plk-2 mutant exhibit the more highly dynamic SC state. Together our data demonstrate that crossover recombination events elicit chromosome-autonomous stabilizing effects on the SC and implicate PLK-2 in this process. We discuss how this recombination-triggered modulation of SC state might contribute to regulatory mechanisms that operate during meiosis to ensure the formation of crossovers while at the same time limiting their numbers. PMID:28339470

Space Life Support Engineering Program

NASA Technical Reports Server (NTRS)

Seagrave, Richard C.

1993-01-01

This report covers the second year of research relating to the development of closed-loop long-term life support systems. Emphasis was directed toward concentrating on the development of dynamic simulation techniques and software and on performing a thermodynamic systems analysis in an effort to begin optimizing the system needed for water purification. Four appendices are attached. The first covers the ASPEN modeling of the closed loop Environmental Control Life Support System (ECLSS) and its thermodynamic analysis. The second is a report on the dynamic model development for water regulation in humans. The third regards the development of an interactive computer-based model for determining exercise limitations. The fourth attachment is an estimate of the second law thermodynamic efficiency of the various units comprising an ECLSS.

Effects of Preferential Solvation Revealed by Time-Resolved Magnetic Field Effects

PubMed Central

2017-01-01

External magnetic fields can impact recombination yields of photoinduced electron transfer reactions by affecting the spin dynamics in transient, spin-correlated radical pair intermediates. For exciplex-forming donor–acceptor systems, this magnetic field effect (MFE) can be investigated sensitively by studying the delayed recombination fluorescence. Here, we investigate the effect of preferential solvation in microheterogeneous solvent mixtures on the radical pair dynamics of the system 9,10-dimethylanthracene (fluorophore)/N,N-dimethylaniline (quencher) by means of time-resolved magnetic field effect (TR-MFE) measurements, wherein the exciplex emission is recorded in the absence and the presence of an external magnetic field using time-correlated single photon counting (TCSPC). In microheterogeneous environments, the MFE of the exciplex emission occurs on a faster time scale than in iso-dielectric homogeneous solvents. In addition, the local polarity reported by the exciplex is enhanced compared to homogeneous solvent mixtures of the same macroscopic permittivity. Detailed analyses of the TR-MFE reveal that the quenching reaction directly yielding the radical ion pair is favored in microheterogeneous environments. This is in stark contrast to homogeneous media, for which the MFE predominantly involves direct formation of the exciplex, its subsequent dissociation to the magneto-sensitive radical pair, and re-encounters. These observations provide evidence for polar microdomains and enhanced caging, which are shown to have a significant impact on the reaction dynamics in microheterogeneous binary solvents. PMID:28263599

Effects of Preferential Solvation Revealed by Time-Resolved Magnetic Field Effects.

PubMed

Pham, Van Thi Bich; Hoang, Hao Minh; Grampp, Günter; Kattnig, Daniel R

2017-03-30

External magnetic fields can impact recombination yields of photoinduced electron transfer reactions by affecting the spin dynamics in transient, spin-correlated radical pair intermediates. For exciplex-forming donor-acceptor systems, this magnetic field effect (MFE) can be investigated sensitively by studying the delayed recombination fluorescence. Here, we investigate the effect of preferential solvation in microheterogeneous solvent mixtures on the radical pair dynamics of the system 9,10-dimethylanthracene (fluorophore)/N,N-dimethylaniline (quencher) by means of time-resolved magnetic field effect (TR-MFE) measurements, wherein the exciplex emission is recorded in the absence and the presence of an external magnetic field using time-correlated single photon counting (TCSPC). In microheterogeneous environments, the MFE of the exciplex emission occurs on a faster time scale than in iso-dielectric homogeneous solvents. In addition, the local polarity reported by the exciplex is enhanced compared to homogeneous solvent mixtures of the same macroscopic permittivity. Detailed analyses of the TR-MFE reveal that the quenching reaction directly yielding the radical ion pair is favored in microheterogeneous environments. This is in stark contrast to homogeneous media, for which the MFE predominantly involves direct formation of the exciplex, its subsequent dissociation to the magneto-sensitive radical pair, and re-encounters. These observations provide evidence for polar microdomains and enhanced caging, which are shown to have a significant impact on the reaction dynamics in microheterogeneous binary solvents.

Dynamic Testing of Signal Transduction Deregulation During Breast Cancer Initiation

DTIC Science & Technology

2011-07-01

1 at a chamber pressure of ~3 × 10-6 Torr for the electron beam evaporated films. A Hitachi FB2100 Focused Ion Beam milling machine with a gallium ...immobilization. These include physical absorption, layer-by-layer (LBL) assembly, and covalent attachment, and eventually chose the covalent attachment...testing real-time signaling in live breast cancer cells, it is important to evaluate the nanosensors to monitor fluorescent compounds in single

Resonant inelastic collisions of electrons with diatomic molecules

NASA Astrophysics Data System (ADS)

Houfek, Karel

2012-05-01

In this contribution we give a review of applications of the nonlocal resonance theory which has been successfully used for treating the nuclear dynamics of low-energy electron collisions with diatomic molecules over several decades. We give examples and brief explanations of various structures observed in the cross sections of vibrational excitation and dissociative electron attachment to diatomic molecules such as threshold peaks, boomerang oscillations below the dissociative attachment threshold, or outer-well resonances.

Molecular dynamic simulations of the intergranular films between alumina and silicon nitride crystal grains

NASA Astrophysics Data System (ADS)

Zhang, Shenghong

The intergranular films (IGFs) between the ceramics grains have very important effects on the structure and mechanical properties on the whole ceramics and have been studied for many decades. In the thesis, molecular dynamic (MD) computer simulations were applied to study the IGFs between the alumina and silicon nitride ceramic grains. Preferential adsorption of specific ions from the IGFs to the contacting surfaces of the alumina crystals was observed in the study of calcium-alumino-silicate glassy (CAS) IGFs formed between the combined basal and prism orientations of alpha-Al2O3 crystals. This segregation of specific ions to the interface enables formation of localized, ordered structures between the IGF and the crystals. However, the segregation behavior of the ions is anisotropic, depending on the orientation of the alpha-Al2O 3 crystals. Self-diffusion of calcium ions between these CAS IGFs was also carried out by MD simulations. The results show that the diffusion coefficients adjacent to the interfaces are smaller and the activation energies are much higher than those in the interior of the IGF and in bulk glasses. It was also suggested that Ca transport is mainly though the interior of the IGF and implies that diffusion would be significantly inhibited by sufficiently thin IGFs. The growth of the alumina ceramic grains was simulated in the contacting with IGFs containing high concentrations of aluminum ions. Five different compositions in the IGFs were studied. Results show preferential growth along the [1120] of the (1120) surface in comparison to growth along the [0001] direction on the (0001) surface for compositions near a Ca/Al ratio of 0.5. The simulations also show the mechanism by which Ca ions in the IGF inhibit growth on the basal surface. The simulations provide an atomistic view of attachment onto crystal surfaces, affecting grain growth in alumina. The dissolution of the alumina crystal grains in the silicate melts is another important issue in the application of alumina ceramics. The simulations results showed that alumina grains dissolved into the melts homogeneously at very high temperatures. The orientation of the crystals and the compositions of the melts only take effect at some intermediate temperatures, to make the alumina grains dissolution anisotropic. The fracture phenomena of the pure silica IGFs between the basal silicon nitride crystals were studied by applying the constant tensile strain on the simulated IGF system, as well as for the bulk silica glass for the comparison. The data indicated that the fracture was happened in the interior of the IGFs and the thickness of the IGFs has important effect on the fracture stress/strain relationships.

Obtaining information by dynamic (effortful) touching

PubMed Central

Turvey, M. T.; Carello, Claudia

2011-01-01

Dynamic touching is effortful touching. It entails deformation of muscles and fascia and activation of the embedded mechanoreceptors, as when an object is supported and moved by the body. It is realized as exploratory activities that can vary widely in spatial and temporal extents (a momentary heft, an extended walk). Research has revealed the potential of dynamic touching for obtaining non-visual information about the body (e.g. limb orientation), attachments to the body (e.g. an object's height and width) and the relation of the body both to attachments (e.g. hand's location on a grasped object) and surrounding surfaces (e.g. places and their distances). Invariants over the exploratory activity (e.g. moments of a wielded object's mass distribution) seem to ground this ‘information about’. The conception of a haptic medium as a nested tensegrity structure has been proposed to express the obtained information realized by myofascia deformation, by its invariants and transformations. The tensegrity proposal rationalizes the relative indifference of dynamic touch to the site of mechanical contact (hand, foot, torso or probe) and the overtness of exploratory activity. It also provides a framework for dynamic touching's fractal nature, and the finding that its degree of fractality may matter to its accomplishments. PMID:21969694

Single-molecule dynamics in nanofabricated traps

NASA Astrophysics Data System (ADS)

Cohen, Adam

2009-03-01

The Anti-Brownian Electrokinetic trap (ABEL trap) provides a means to immobilize a single fluorescent molecule in solution, without surface attachment chemistry. The ABEL trap works by tracking the Brownian motion of a single molecule, and applying feedback electric fields to induce an electrokinetic motion that approximately cancels the Brownian motion. We present a new design for the ABEL trap that allows smaller molecules to be trapped and more information to be extracted from the dynamics of a single molecule than was previously possible. In particular, we present strategies for extracting dynamically fluctuating mobilities and diffusion coefficients, as a means to probe dynamic changes in molecular charge and shape. If one trapped molecule is good, many trapped molecules are better. An array of single molecules in solution, each immobilized without surface attachment chemistry, provides an ideal test-bed for single-molecule analyses of intramolecular dynamics and intermolecular interactions. We present a technology for creating such an array, using a fused silica plate with nanofabricated dimples and a removable cover for sealing single molecules within the dimples. With this device one can watch the shape fluctuations of single molecules of DNA or study cooperative interactions in weakly associating protein complexes.

Transitions in sensitive period attachment learning in infancy: the role of corticosterone.

PubMed

Sullivan, Regina M; Holman, Parker J

2010-05-01

Survival of altricial infants, including humans and rats, depends on attachment to the caregiver - a process that requires infants to recognize, learn, and remember their attachment figure. The demands of a dynamic environment combined with a maturing organism require frequent neurobehavioral reorganization. This restructuring of behavior and its supporting neural circuitry can be viewed through the unique lens of attachment learning in rats in which preference learning is enhanced and aversion learning is attenuated. Behavioral restructuring is well adapted to securing the crucial infant-caregiver relationship regardless of the quality of care. With maturation and the end of the infant-caregiver attachment learning period, the complex interplay of neural structures, hormones, and social behavior coordinates the developing rat's eventual transition to life outside of the nest. Nevertheless, early-life environmental and physiological stressors can alter the resilient nature of this system, particularly with respect to the amygdala, and these changes may provide important clues to understanding the lasting effects of early stress. (c) 2009 Elsevier Ltd. All rights reserved.

Emotional attachments in abusive relationships: a test of traumatic bonding theory.

PubMed

Dutton, D G; Painter, S

1993-01-01

An empirical test of traumatic bonding theory, the notion that strong emotional attachments are formed by intermittent abuse, is reported. In-depth assessments (interviews plus questionnaires) were conducted on 75 women who had recently left abusive relationships (50 where physical violence had occurred). The study found support for the effect of relationship dynamic factors such as extremity of intermittent maltreatment and power differentials on long-term felt attachment for a former partner, experienced trauma symptoms, and self-esteem, immediately after separation from an abusive partner and again after a six month interim. All three of these measures were significantly intercorrelated within each time period. Each measure at Time 1 correlated significantly with each corresponding measure at Time 2. After six months attachment had decreased by about 27%. Relationship variables (total abuse, intermittency of abuse and power differentials) accounted for 55% of the variance in the attachment measure at Time 2 indicating prolonged effects of abuse suffered in the relationship.

Hemolytic potential of hydrodynamic cavitation.

PubMed

Chambers, S D; Bartlett, R H; Ceccio, S L

2000-08-01

The purpose of this study was to determine the hemolytic potentials of discrete bubble cavitation and attached cavitation. To generate controlled cavitation events, a venturigeometry hydrodynamic device, called a Cavitation Susceptibility Meter (CSM), was constructed. A comparison between the hemolytic potential of discrete bubble cavitation and attached cavitation was investigated with a single-pass flow apparatus and a recirculating flow apparatus, both utilizing the CSM. An analytical model, based on spherical bubble dynamics, was developed for predicting the hemolysis caused by discrete bubble cavitation. Experimentally, discrete bubble cavitation did not correlate with a measurable increase in plasma-free hemoglobin (PFHb), as predicted by the analytical model. However, attached cavitation did result in significant PFHb generation. The rate of PFHb generation scaled inversely with the Cavitation number at a constant flow rate, suggesting that the size of the attached cavity was the dominant hemolytic factor.

The Association of Cryptosporidium parvum With Suspended Sediments: Implications for Transport in Surface Waters

NASA Astrophysics Data System (ADS)

Searcy, K. E.; Packman, A. I.; Atwill, E. R.; Harter, T.

2003-12-01

Understanding the transport and fate of microorganisms in surface waters is of vital concern in protecting the integrity and safety of municipal water supply systems. The human pathogen Cryptosporidium parvum is a particular public health interest, as it is ubiquitous in the surface waters of the United States, it can persist for long periods in the environment, and it is difficult to disinfect in water treatment plants. Due to its small size (5 um), low specific gravity (1.05 g/cm3), and negative surface charge, C. parvum oocysts are generally considered to move through watersheds from their source to drinking water reservoirs with little attenuation. However, the transport of the oocysts in surface waters may be mediated by interactions with suspended sediments. Batch experiments were conducted to determine the extent of C. parvum oocyst attachment to several inorganic and organic sediments under varying water chemical conditions, and settling column experiments were performed to demonstrate how these associations influence the effective settling velocity of C. parvum oocysts. Results from these experiments showed that C. parvum oocysts do associate with inorganic and organic sediments and often settle at the rate of the suspended sediment. The size and surface charge of the host suspended sediment influenced the extent of oocyst attachment as oocysts preferentially associated with particles greater than 3 um, and fewer oocysts associated with particles having a highly negative surface charge. Background water chemical conditions including ionic strength, ion composition, and pH did not have a significant effect on oocyst attachment to suspended sediments.

Modeling and dynamical topology properties of VANET based on complex networks theory

NASA Astrophysics Data System (ADS)

Zhang, Hong; Li, Jie

2015-01-01

Vehicular Ad hoc Network (VANET) is a special subset of multi-hop Mobile Ad hoc Networks in which vehicles can not only communicate with each other but also with the fixed equipments along the roads through wireless interfaces. Recently, it has been discovered that essential systems in real world share similar properties. When they are regarded as networks, among which the dynamic topology structure of VANET system is an important issue. Many real world networks are actually growing with preferential attachment like Internet, transportation system and telephone network. Those phenomena have brought great possibility in finding a strategy to calibrate and control the topology parameters which can help find VANET topology change regulation to relieve traffic jam, prevent traffic accident and improve traffic safety. VANET is a typical complex network which has its basic characteristics. In this paper, we focus on the macroscopic Vehicle-to-Infrastructure (V2I) and Vehicle-to-Vehicle (V2V) inter-vehicle communication network with complex network theory. In particular, this paper is the first one to propose a method analyzing the topological structure and performance of VANET and present the communications in VANET from a new perspective. Accordingly, we propose degree distribution, clustering coefficient and the short path length of complex network to implement our strategy by numerical example and simulation. All the results demonstrate that VANET shows small world network features and is characterized by a truncated scale-free degree distribution with power-law degree distribution. The average path length of the network is simulated numerically, which indicates that the network shows small-world property and is rarely affected by the randomness. What's more, we carry out extensive simulations of information propagation and mathematically prove the power law property when γ > 2. The results of this study provide useful information for VANET optimization from a macroscopic perspective.

Modeling and dynamical topology properties of VANET based on complex networks theory

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

Zhang, Hong; Li, Jie, E-mail: prof.li@foxmail.com

2015-01-15

Vehicular Ad hoc Network (VANET) is a special subset of multi-hop Mobile Ad hoc Networks in which vehicles can not only communicate with each other but also with the fixed equipments along the roads through wireless interfaces. Recently, it has been discovered that essential systems in real world share similar properties. When they are regarded as networks, among which the dynamic topology structure of VANET system is an important issue. Many real world networks are actually growing with preferential attachment like Internet, transportation system and telephone network. Those phenomena have brought great possibility in finding a strategy to calibrate andmore » control the topology parameters which can help find VANET topology change regulation to relieve traffic jam, prevent traffic accident and improve traffic safety. VANET is a typical complex network which has its basic characteristics. In this paper, we focus on the macroscopic Vehicle-to-Infrastructure (V2I) and Vehicle-to-Vehicle (V2V) inter-vehicle communication network with complex network theory. In particular, this paper is the first one to propose a method analyzing the topological structure and performance of VANET and present the communications in VANET from a new perspective. Accordingly, we propose degree distribution, clustering coefficient and the short path length of complex network to implement our strategy by numerical example and simulation. All the results demonstrate that VANET shows small world network features and is characterized by a truncated scale-free degree distribution with power-law degree distribution. The average path length of the network is simulated numerically, which indicates that the network shows small-world property and is rarely affected by the randomness. What’s more, we carry out extensive simulations of information propagation and mathematically prove the power law property when γ > 2. The results of this study provide useful information for VANET optimization from a macroscopic perspective.« less

Analytical solution and numerical study on water hammer in a pipeline closed with an elastically attached valve

NASA Astrophysics Data System (ADS)

Henclik, Sławomir

2018-03-01

The influence of dynamic fluid-structure interaction (FSI) onto the course of water hammer (WH) can be significant in non-rigid pipeline systems. The essence of this effect is the dynamic transfer of liquid energy to the pipeline structure and back, which is important for elastic structures and can be negligible for rigid ones. In the paper a special model of such behavior is analyzed. A straight pipeline with a steady flow, fixed to the floor with several rigid supports is assumed. The transient is generated by a quickly closed valve installed at the end of the pipeline. FSI effects are assumed to be present mainly at the valve which is fixed with a spring dash-pot attachment. Analysis of WH runs, especially transient pressure changes, for various stiffness and damping parameters of the spring dash-pot valve attachment is presented in the paper. The solutions are found analytically and numerically. Numerical results have been computed with the use of an own computer program developed on the basis of the four equation model of WH-FSI and the specific boundary conditions formulated at the valve. Analytical solutions have been found with the separation of variables method for slightly simplified assumptions. Damping at the dash-pot is taken into account within the numerical study. The influence of valve attachment parameters onto the WH courses was discovered and it was found the transient amplitudes can be reduced. Such a system, elastically attached shut-off valve in a pipeline or other, equivalent design can be a real solution applicable in practice.

Crystallization dynamics on curved surfaces

NASA Astrophysics Data System (ADS)

García, Nicolás A.; Register, Richard A.; Vega, Daniel A.; Gómez, Leopoldo R.

2013-07-01

We study the evolution from a liquid to a crystal phase in two-dimensional curved space. At early times, while crystal seeds grow preferentially in regions of low curvature, the lattice frustration produced in regions with high curvature is rapidly relaxed through isolated defects. Further relaxation involves a mechanism of crystal growth and defect annihilation where regions with high curvature act as sinks for the diffusion of domain walls. The pinning of grain boundaries at regions of low curvature leads to the formation of a metastable structure of defects, characterized by asymptotically slow dynamics of ordering and activation energies dictated by the largest curvatures of the system. These glassylike ordering dynamics may completely inhibit the appearance of the ground-state structures.

A generative model for scientific concept hierarchies.

PubMed

Datta, Srayan; Adar, Eytan

2018-01-01

In many scientific disciplines, each new 'product' of research (method, finding, artifact, etc.) is often built upon previous findings-leading to extension and branching of scientific concepts over time. We aim to understand the evolution of scientific concepts by placing them in phylogenetic hierarchies where scientific keyphrases from a large, longitudinal academic corpora are used as a proxy of scientific concepts. These hierarchies exhibit various important properties, including power-law degree distribution, power-law component size distribution, existence of a giant component and less probability of extending an older concept. We present a generative model based on preferential attachment to simulate the graphical and temporal properties of these hierarchies which helps us understand the underlying process behind scientific concept evolution and may be useful in simulating and predicting scientific evolution.

Social power and opinion formation in complex networks

NASA Astrophysics Data System (ADS)

Jalili, Mahdi

2013-02-01

In this paper we investigate the effects of social power on the evolution of opinions in model networks as well as in a number of real social networks. A continuous opinion formation model is considered and the analysis is performed through numerical simulation. Social power is given to a proportion of agents selected either randomly or based on their degrees. As artificial network structures, we consider scale-free networks constructed through preferential attachment and Watts-Strogatz networks. Numerical simulations show that scale-free networks with degree-based social power on the hub nodes have an optimal case where the largest number of the nodes reaches a consensus. However, given power to a random selection of nodes could not improve consensus properties. Introducing social power in Watts-Strogatz networks could not significantly change the consensus profile.

Origin and implications of zero degeneracy in networks spectra.

PubMed

Yadav, Alok; Jalan, Sarika

2015-04-01

The spectra of many real world networks exhibit properties which are different from those of random networks generated using various models. One such property is the existence of a very high degeneracy at the zero eigenvalue. In this work, we provide all the possible reasons behind the occurrence of the zero degeneracy in the network spectra, namely, the complete and partial duplications, as well as their implications. The power-law degree sequence and the preferential attachment are the properties which enhances the occurrence of such duplications and hence leading to the zero degeneracy. A comparison of the zero degeneracy in protein-protein interaction networks of six different species and in their corresponding model networks indicates importance of the degree sequences and the power-law exponent for the occurrence of zero degeneracy.

A generative model for scientific concept hierarchies

PubMed Central

Adar, Eytan

2018-01-01

In many scientific disciplines, each new ‘product’ of research (method, finding, artifact, etc.) is often built upon previous findings–leading to extension and branching of scientific concepts over time. We aim to understand the evolution of scientific concepts by placing them in phylogenetic hierarchies where scientific keyphrases from a large, longitudinal academic corpora are used as a proxy of scientific concepts. These hierarchies exhibit various important properties, including power-law degree distribution, power-law component size distribution, existence of a giant component and less probability of extending an older concept. We present a generative model based on preferential attachment to simulate the graphical and temporal properties of these hierarchies which helps us understand the underlying process behind scientific concept evolution and may be useful in simulating and predicting scientific evolution. PMID:29474409

Local versus global knowledge in the Barabási-Albert scale-free network model.

PubMed

Gómez-Gardeñes, Jesús; Moreno, Yamir

2004-03-01

The scale-free model of Barabási and Albert (BA) gave rise to a burst of activity in the field of complex networks. In this paper, we revisit one of the main assumptions of the model, the preferential attachment (PA) rule. We study a model in which the PA rule is applied to a neighborhood of newly created nodes and thus no global knowledge of the network is assumed. We numerically show that global properties of the BA model such as the connectivity distribution and the average shortest path length are quite robust when there is some degree of local knowledge. In contrast, other properties such as the clustering coefficient and degree-degree correlations differ and approach the values measured for real-world networks.

Modelling soil-water dynamics in the rootzone of structured and water-repellent soils

NASA Astrophysics Data System (ADS)

Brown, Hamish; Carrick, Sam; Müller, Karin; Thomas, Steve; Sharp, Joanna; Cichota, Rogerio; Holzworth, Dean; Clothier, Brent

2018-04-01

In modelling the hydrology of Earth's critical zone, there are two major challenges. The first is to understand and model the processes of infiltration, runoff, redistribution and root-water uptake in structured soils that exhibit preferential flows through macropore networks. The other challenge is to parametrise and model the impact of ephemeral hydrophobicity of water-repellent soils. Here we have developed a soil-water model, which is based on physical principles, yet possesses simple functionality to enable easier parameterisation, so as to predict soil-water dynamics in structured soils displaying time-varying degrees of hydrophobicity. Our model, WEIRDO (Water Evapotranspiration Infiltration Redistribution Drainage runOff), has been developed in the APSIM Next Generation platform (Agricultural Production Systems sIMulation). The model operates on an hourly time-step. The repository for this open-source code is https://github.com/APSIMInitiative/ApsimX. We have carried out sensitivity tests to show how WEIRDO predicts infiltration, drainage, redistribution, transpiration and soil-water evaporation for three distinctly different soil textures displaying differing hydraulic properties. These three soils were drawn from the UNSODA (Unsaturated SOil hydraulic Database) soils database of the United States Department of Agriculture (USDA). We show how preferential flow process and hydrophobicity determine the spatio-temporal pattern of soil-water dynamics. Finally, we have validated WEIRDO by comparing its predictions against three years of soil-water content measurements made under an irrigated alfalfa (Medicago sativa L.) trial. The results provide validation of the model's ability to simulate soil-water dynamics in structured soils.

How ticks get under your skin: insertion mechanics of the feeding apparatus of Ixodes ricinus ticks

PubMed Central

Richter, Dania; Matuschka, Franz-Rainer; Spielman, Andrew; Mahadevan, L.

2013-01-01

The tick Ixodes ricinus uses its mouthparts to penetrate the skin of its host and to remain attached for about a week, during which time Lyme disease spirochaetes may pass from the tick to the host. To understand how the tick achieves both tasks, penetration and attachment, with the same set of implements, we recorded the insertion events by cinematography, interpreted the mouthparts’ function by scanning electron microscopy and identified their points of articulation by confocal microscopy. Our structural dynamic observations suggest that the process of insertion and attachment occurs via a ratchet-like mechanism with two distinct stages. Initially, the two telescoping chelicerae pierce the skin and, by moving alternately, generate a toehold. Subsequently, a breaststroke-like motion, effected by simultaneous flexure and retraction of both chelicerae, pulls in the barbed hypostome. This combination of a flexible, dynamic mechanical ratchet and a static holdfast thus allows the tick to solve the problem of how to penetrate skin and also remain stuck for long periods of time. PMID:24174106

The static structure and dynamics of cadmium sulfide nanoparticles within poly(styrene- block-isoprene) diblock copolymer melts

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

Jang, Woo -Sik; Koo, Peter; Bryson, Kyle

Here, the static structure and dynamic behavior of cadmium sulfide nanoparticles suspended in block copolymer matrix are investigated using transmission electron microscopy, small-angle X-ray scattering, and X-ray photon correlation spectroscopy. The transmission electron micro- scopy study shows that cadmium sulfide nanoparticles are preferentially segregated within the polyisoprene domain of a poly(styrene- block-isoprene) diblock copolymer. For the dynamics study, X-ray photon correlation spectroscopy captures the relaxation process of cadmium sulfide nanoparticles. The measured characteristic relaxation time reveals that the observed dynamics are hyperdiffusive. The characteristic velocity and corresponding activation energy, which are hallmarks of a hyperdiffusive system, are determined from themore » relationship between the characteristic relaxation time and the wavevector.« less

The static structure and dynamics of cadmium sulfide nanoparticles within poly(styrene- block-isoprene) diblock copolymer melts

DOE PAGES

Jang, Woo -Sik; Koo, Peter; Bryson, Kyle; ...

2015-12-20

Here, the static structure and dynamic behavior of cadmium sulfide nanoparticles suspended in block copolymer matrix are investigated using transmission electron microscopy, small-angle X-ray scattering, and X-ray photon correlation spectroscopy. The transmission electron micro- scopy study shows that cadmium sulfide nanoparticles are preferentially segregated within the polyisoprene domain of a poly(styrene- block-isoprene) diblock copolymer. For the dynamics study, X-ray photon correlation spectroscopy captures the relaxation process of cadmium sulfide nanoparticles. The measured characteristic relaxation time reveals that the observed dynamics are hyperdiffusive. The characteristic velocity and corresponding activation energy, which are hallmarks of a hyperdiffusive system, are determined from themore » relationship between the characteristic relaxation time and the wavevector.« less

Evaluation of affinity and pseudo-affinity adsorption processes for penicillin acylase purification.

PubMed

Fonseca, L P; Cabral, J M

1996-01-01

Affinity ligand (6-Aminopenicillanic acid, Amoxycillin, Ampicillin, Benzylpenicillin and 4-Phenylbutylanzine) of penicillin acylase (EC 3.5.1.11) were attached to hydrophilic gels like Sepharose 4B-CNBr and Minileak 'medium'. Ampicillin and 4-Phenylbutylamine were the affinity ligands that presented the higher concentrations attached to both gels. Penicillin acylase adsorption on these affinity gels was mainly dependent on the activated group of the gel, the affinity ligand attached and the experimental conditions of enzyme adsorption. Under affinity conditions only the ligands Amoxycillin, Ampicillin and 4-Phenylbutylamine, immobilized on Minileak, adsorbed the enzyme from osmotic shock extracts at different pH values. These affinity ligand systems were characterized by low adsorption capacities of penicillin acylase activity (1.2-2.1 IU mL-1 gel) and specific activity (1.5-2.9 IU mg-1 prot). Under pseudo-affinity conditions all the ligands attached both activated to gels (Sepharose 4B-CNBr and Minileak) adsorbed the enzyme. The affinity gels were characterized by higher values of adsorption capacity (3.7 and 55.6 IU mL-1 gel) and adsorbed specific activity (2.0 and 6.1 IU mg-1 prot) than those observed under affinity conditions. The space arm of Minileak gel, shown to be fundamental to enzyme adsorption under affinity conditions, preferentially adsorbed proteins in relation to the enzyme under pseudo-affinity conditions. However, this effect was partially minimized when the gel was derivatized by the affinity ligands at concentrations higher than 6 mumol mL-1 gel. Ampicillin was the affinity ligand that presented the best results for specific adsorption of penicillin acylase under affinity and pseudo-affinity adsorption processes. The Sepharose 4B-CNBr derivatized gel also presented a good adsorption capacity of enzyme activity (26.8 IU mL-1 gel) under pseudo-affinity adsorption processes.

Infiltration Processes and Flow Velocities Across the Landscape: When and Where is Macropore Flow Relevant?

NASA Astrophysics Data System (ADS)

Demand, D.; Blume, T.; Weiler, M.

2017-12-01

Preferential flow in macropores significantly affects the distributions of water and solutes in soil and many studies showed its relevance worldwide. Although some models include this process as a second pore domain, little is known about the spatial patterns and temporal dynamics. For example, while flow in the matrix is usually modeled and parameterized based on soil texture, an influence of texture on non-capillary flow for a given land-use class is poorly understood. To investigate the temporal and spatial dynamics on preferential flow we used a four-year soil moisture dataset from the mesoscale Attert catchment (288 km²) in Luxembourg. This dataset contains time series from 126 soil profiles in different textures and two land-use classes (forest, grassland). The soil moisture probes were installed in 10, 30 and 50 cm depth and measured in a 5-minute temporal resolution. Events were defined by a soil moisture increase higher than the instrument noise after a precipitation sum of more than 1 mm. Precipitation was measured next to the profiles so that each location could be associated to its unique precipitation characteristics. For every event and profile the soil moisture reaction was classified in sequential (ordered by depth) and non-sequential response. A non-sequential soil moisture reaction was used as an indicator of preferential flow. For sequential flow, the velocity was determined by the first reaction between two vertically adjacent sensors. The sensor reaction and wetting front velocity was analyzed in the context of precipitation characteristics and initial soil water content. Grassland sites showed a lower proportion of non-sequential flow than forest sites. For forest, non-sequential response is dependent on texture, rainfall intensity and initial water content. This is less distinct for the grassland sites. Furthermore, sequential reactions show higher flow velocities at sites, which also have high percentage of non-sequential response. In contrast, grassland sites show a more homogenous wetting front independent of soil texture. Compared against common modelling approaches of soil water flow, measured velocities show clear evidence of preferential flow, especially for forest soils. The analysis also shows that vegetation can alter the soil properties above the textural properties alone.

Preferential stabilization of newly formed dendritic spines in motor cortex during manual skill learning predicts performance gains, but not memory endurance.

PubMed

Clark, Taylor A; Fu, Min; Dunn, Andrew K; Zuo, Yi; Jones, Theresa A

2018-07-01

Previous findings that skill learning is associated with the formation and preferential stabilization of new dendritic spines in cortex have raised the possibility that this preferential stabilization is a mechanism for lasting skill memory. We investigated this possibility in adult mice using in vivo two-photon imaging to monitor spine dynamics on superficial apical dendrites of layer V pyramidal neurons in motor cortex during manual skill learning. Spine formation increased over the first 3 days of training on a skilled reaching task, followed by increased spine elimination. A greater proportion of spines formed during the first 3 training days were lost if training stopped after 3, compared with 15 days. However, performance gains achieved in 3 training days persisted, indicating that preferential new spine stabilization was non-essential for skill retention. Consistent with a role in ongoing skill refinement, the persistence of spines formed early in training strongly predicted performance improvements. Finally, while we observed no net spine density change on superficial dendrites, the density of spines on deeper apical branches of the same neuronal population was increased regardless of training duration, suggestive of a potential role in the retention of the initial skill memory. Together, these results indicate dendritic subpopulation-dependent variation in spine structural responses to skill learning, which potentially reflect distinct contributions to the refinement and retention of newly acquired motor skills. Copyright © 2018 Elsevier Inc. All rights reserved.

Vibration analysis of rotor blades with an attached concentrated mass

NASA Technical Reports Server (NTRS)

Murthy, V. R.; Barna, P. S.

1977-01-01

The effect of an attached concentrated mass on the dynamics of helicopter rotor blades is determined. The point transmission matrix method was used to define, through three completely automated computer programs, the natural vibrational characteristics (natural frequencies and mode shapes) of rotor blades. The problems of coupled flapwise bending, chordwise bending, and torsional vibration of a twisted nonuniform blade and its special subcase pure torsional vibration are discussed. The orthogonality relations that exist between the natural modes of rotor blades with an attached concentrated mass are derived. The effect of pitch, rotation, and point mass parameters on the collective, cyclic, scissor, and pure torsional modes of a seesaw rotor blade is determined.

Dissociative electron attachment and vibrational excitation of CF{sub 3}Cl: Effect of two vibrational modes revisited

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

Tarana, Michal; JILA, University of Colorado and NIST, Boulder, Colorado 80309-0440; Houfek, Karel

We present a study of dissociative electron attachment and vibrational excitation processes in electron collisions with the CF{sub 3}Cl molecule. The calculations are based on the two-dimensional nuclear dynamics including the C-Cl symmetric stretch coordinate and the CF{sub 3} symmetric deformation (umbrella) coordinate. The complex potential energy surfaces are calculated using the ab initio R-matrix method. The results for dissociative attachment and vibrational excitation of the umbrella mode agree quite well with experiment whereas the cross section for excitation of the C-Cl symmetric stretch vibrations is about a factor-of-three too low in comparison with experimental data.

TAO1 kinase maintains chromosomal stability by facilitating proper congression of chromosomes

PubMed Central

Shrestha, Roshan L.; Tamura, Naoka; Fries, Anna; Levin, Nicolas; Clark, Joanna; Draviam, Viji M.

2014-01-01

Chromosomal instability can arise from defects in chromosome–microtubule attachment. Using a variety of drug treatments, we show that TAO1 kinase is required for ensuring the normal congression of chromosomes. Depletion of TAO1 reduces the density of growing interphase and mitotic microtubules in human cells, showing TAO1's role in controlling microtubule dynamics. We demonstrate the aneugenic nature of chromosome–microtubule attachment defects in TAO1-depleted cells using an error-correction assay. Our model further strengthens the emerging paradigm that microtubule regulatory pathways are important for resolving erroneous kinetochore–microtubule attachments and maintaining the integrity of the genome, regardless of the spindle checkpoint status. PMID:24898139

Action-derived molecular dynamics simulations for the migration and coalescence of vacancies in graphene and carbon nanotubes.

PubMed

Lee, Alex Taekyung; Ryu, Byungki; Lee, In-Ho; Chang, K J

2014-03-19

We report the results of action-derived molecular dynamics simulations for the migration and coalescence processes of monovacancies in graphene and carbon nanotubes with different chiralities. In carbon nanotubes, the migration pathways and barriers of a monovacancy depend on the tube chirality, while there is no preferential pathway in graphene due to the lattice symmetry and the absence of the curvature effect. The probable pathway changes from the axial to circumferential direction as the chirality varies from armchair to zigzag. The chirality dependence is attributed to the preferential orientation of the reconstructed bond formed around each vacancy site. It is energetically more favourable for two monovacancies to coalesce into a divacancy via alternative movements rather than simultaneous movements. The energy barriers for coalescence are generally determined by the migration barrier for the monovacancy, although there are some variations due to interactions between two diffusing vacancies. In graphene and armchair nanotubes, two monovacancies prefer to migrate along different zigzag atomic chains rather than a single atomic chain connecting these vacancies. On the other hand, in zigzag tubes, the energy barrier for coalescence increases significantly unless monovacancies lie on the same circumference.

Knowledge diffusion of dynamical network in terms of interaction frequency.

PubMed

Liu, Jian-Guo; Zhou, Qing; Guo, Qiang; Yang, Zhen-Hua; Xie, Fei; Han, Jing-Ti

2017-09-07

In this paper, we present a knowledge diffusion (SKD) model for dynamic networks by taking into account the interaction frequency which always used to measure the social closeness. A set of agents, which are initially interconnected to form a random network, either exchange knowledge with their neighbors or move toward a new location through an edge-rewiring procedure. The activity of knowledge exchange between agents is determined by a knowledge transfer rule that the target node would preferentially select one neighbor node to transfer knowledge with probability p according to their interaction frequency instead of the knowledge distance, otherwise, the target node would build a new link with its second-order neighbor preferentially or select one node in the system randomly with probability 1 - p. The simulation results show that, comparing with the Null model defined by the random selection mechanism and the traditional knowledge diffusion (TKD) model driven by knowledge distance, the knowledge would spread more fast based on SKD driven by interaction frequency. In particular, the network structure of SKD would evolve as an assortative one, which is a fundamental feature of social networks. This work would be helpful for deeply understanding the coevolution of the knowledge diffusion and network structure.

Clustering and entrainment effects on the evaporation of dilute droplets in a turbulent jet

NASA Astrophysics Data System (ADS)

Dalla Barba, Federico; Picano, Francesco

2018-03-01

The evaporation of droplets within turbulent sprays involves unsteady, multiscale, and multiphase processes which make its comprehension and modeling capabilities still limited. The present work aims to investigate the dynamics of droplet vaporization within a turbulent spatial developing jet in dilute, nonreacting conditions. We address the problem considering a turbulent jet laden with acetone droplets and using the direct numerical simulation framework based on a hybrid Eulerian-Lagrangian approach and the point droplet approximation. A detailed statistical analysis of both phases is presented. In particular, we show how crucial is the preferential sampling of the vapor phase induced by the inhomogeneous localization of the droplets through the flow. Strong droplet preferential segregation develops suddenly downstream from the inflow section both within the turbulent core and the jet mixing layer. Two distinct mechanisms have been found to drive this phenomenon: the inertial small-scale clustering in the jet core and the intermittent dynamics of droplets across the turbulent-nonturbulent interface in the mixing layer, where dry air entrainment occurs. These phenomenologies strongly affect the overall vaporization process and lead to an impressive widening of the droplet size and vaporization rate distributions in the downstream evolution of the turbulent spray.

Split rheometer Couette attachment to enable sample extraction

NASA Astrophysics Data System (ADS)

Guthrie, Sarah E.; Idziak, Stefan H. J.

2005-02-01

We report on the development of a Couette attachment insert for a rheometer, which is designed to split in half, enabling intact sample extraction of cocoa butter crystallized from the melt under known dynamic stress conditions. This cell is capable of producing a sample 1mm thick. At shear rates of 90-720s-1 and final temperatures of 18-20°C it was shown that the sample will completely separate from the cell surface intact.

A Foil Thrust Bearing Test Rig for Evaluation of High Temperature Performance and Durability

DTIC Science & Technology

2008-04-01

composed of similar elements used in journal bearings, but are designed to support a shaft axially. Often, discrete compliant pads are attached... shaft designed to mate with a test thrust runner. The runner is mounted to the shaft with four high strength bolts, and an interference fit ensures...attached to the drive is able to stop the spindle quickly through dynamic braking of the shaft rotational energy. This spindle arrangement has

Are mothers' protective attachment strategies related to their children's strategies?

PubMed

Crittenden, Patricia M; Robson, Katrina; Tooby, Alison; Fleming, Charles

2017-07-01

We explored the relation between mothers' protective attachment strategies and those of their school-age children. In total, 49 child-mother dyads participated in a short longitudinal study when the children were 5.5 and 6.0 years old. Their strategies were first assessed with the Preschool Assessment of Attachment (PAA) and then with the School-age Assessment of Attachment (SAA). Mothers were assessed with the Adult Attachment Interview (AAI). The Dynamic-Maturational Model of Attachment and Adaptation (DMM) was used to classify the assessments. The validity and precision of the DMM-AAI were supported: Mothers' AAI classifications were related to their referral group (normative or clinical) and measures of stress and distress. The DMM categories were more associated with risk than the Ainsworth categories. Types A, C and A/C were differentiated by trauma, triangulation and depression. Mothers' and children's protective attachment strategies were related, with B mothers having B children and A or C mothers having children using the same or opposite strategy. Children whose classification changed from the PAA to the SAA had mothers with complex traumas. When psychosocial treatment is needed, knowing whether mother and child use the same or different strategies and whether mothers have complex trauma can affect treatment success.

Parasite Removal, but Not Herbivory, Deters Future Parasite Attachment on Tomato

PubMed Central

Tjiurutue, Muvari Connie; Palmer-Young, Evan C.; Adler, Lynn S.

2016-01-01

Plants face many antagonistic interactions that occur sequentially. Often, plants employ defense strategies in response to the initial damage that are highly specific and can affect interactions with subsequent antagonists. In addition to herbivores and pathogens, plants face attacks by parasitic plants, but we know little about how prior herbivory compared to prior parasite attachment affects subsequent host interactions. If host plants can respond adaptively to these different damage types, we predict that prior parasitism would have a greater deterrent effect on subsequent parasites than would prior herbivory. To test the effects of prior parasitism and prior herbivory on subsequent parasitic dodder (Cuscuta spp.) preference, we conducted two separate greenhouse studies with tomato hosts (Solanum lycopersicum). In the first experiment, we tested the effects of previous dodder attachment on subsequent dodder preference on tomato hosts using three treatments: control plants that had no previous dodder attachment; dodder-removed plants that had an initial dodder seedling attached, removed and left in the same pot to simulate parasite death; and dodder-continuous plants with an initial dodder seedling that remained attached. In the second experiment, we tested the effects of previous caterpillar damage (Spodoptera exigua) and mechanical damage on future dodder attachment on tomato hosts. Dodder attached most slowly to tomato hosts that had dodder plants previously attached and then removed, compared to control plants or plants with continuous dodder attachment. In contrast, herbivory did not affect subsequent dodder attachment rate. These results indicate that dodder preference depended on the identity and the outcome of the initial attack, suggesting that early-season interactions have the potential for profound impacts on subsequent community dynamics. PMID:27529694

Mutual Exclusion of Urea and Trimethylamine N-oxide from Amino Acids in Mixed Solvent Environment

NASA Astrophysics Data System (ADS)

Ganguly, Pritam; Hajari, Timir; Shea, Joan-Emma; van der Vegt, Nico F. A.

2015-03-01

We study the solvation thermodynamics of individual amino acids in mixed urea and trimethylamine N-oxide (TMAO) solutions using molecular dynamics simulations and the Kirkwood-Buff theory. Our results on the preferential interactions between the amino acids and the cosolvents (urea and TMAO) show a mutual exclusion of both the cosolvents from the amino acid surface in the mixed cosolvent condition which is followed by an increase in the cosolvent-cosolvent aggregation away from the amino acid surface. The effects of the mixed cosolvents on the association of the amino acids and the preferential solvation of the amino acids by water are found to be highly non-linear in terms of the effects of the individual cosolvents. A similar result has been found for the association of the protein backbone, mimicked by triglycine. Our results have been confirmed by different TMAO force-fields and the mutual exclusions of the cosolvents from the amino acids are found to be independent of the choice of the strength of the TMAO-water interactions. Based on our data, a general mechanism can potentially be proposed for the effects of the mixed cosolvents on the preferential solvations of the solutes including the case of cononsolvency.

Groundwater recharge dynamics in unsaturated fractured chalk: a case study

NASA Astrophysics Data System (ADS)

Cherubini, Claudia; Pastore, Nicola; Giasi, Concetta I.; Allegretti, Nicolaetta M.

2016-04-01

The heterogeneity of the unsaturated zone controls its hydraulic response to rainfall and the extent to which pollutants are delayed or attenuated before reaching groundwater. It plays therefore a very important role in the recharge of aquifers and the transfer of pollutants because of the presence of temporary storage zones and preferential flows. A better knowledge of the physical processes in the unsaturated zone would allow an improved assessment of the natural recharge in a heterogeneous aquifer and of its vulnerability to surface-applied pollution. The case study regards the role of the thick unsaturated zone of the Cretaceous chalk aquifer in Picardy (North of France) that controls the hydraulic response to rainfall. In the North Paris Basin, much of the recharge must pass through a regional chalk bed that is composed of a porous matrix with embedded fractures. Different types of conceptual models have been formulated to explain infiltration and recharge processes in the unsaturated fractured rock. The present study analyses the episodic recharge in fractured Chalk aquifer using the kinematic diffusion theory to predict water table fluctuation in response to rainfall. From an analysis of the data, there is the evidence of 1) a seasonal behavior characterized by a constant increase in the water level during the winter/spring period and a recession period, 2) a series of episodic behaviors during the summer/autumn. Kinematic diffusion models are useful for predict preferential fluxes and dynamic conditions. The presented approach conceptualizes the unsaturated flow as a combination of 1) diffusive flow refers to the idealized portion of the pore space of the medium within the flow rate is driven essentially by local gradient of potential; 2) preferential flow by which water moves across macroscopic distances through conduits of macropore length.

Three-Dimensional Smoothed Particle Hydrodynamics Modeling of Preferential Flow Dynamics at Fracture Intersections on a High-Performance Computing Platform

NASA Astrophysics Data System (ADS)

Kordilla, J.; Bresinsky, L. T.

2017-12-01

The physical mechanisms that govern preferential flow dynamics in unsaturated fractured rock formations are complex and not well understood. Fracture intersections may act as an integrator of unsaturated flow, leading to temporal delay, intermittent flow and partitioning dynamics. In this work, a three-dimensional Pairwise-Force Smoothed Particle Hydrodynamics (PF-SPH) model is being applied in order to simulate gravity-driven multiphase flow at synthetic fracture intersections. SPH, as a meshless Lagrangian method, is particularly suitable for modeling deformable interfaces, such as three-phase contact dynamics of droplets, rivulets and free-surface films. The static and dynamic contact angle can be recognized as the most important parameter of gravity-driven free-surface flow. In SPH, surface tension and adhesion naturally emerges from the implemented pairwise fluid-fluid (sff) and solid-fluid (ssf) interaction force. The model was calibrated to a contact angle of 65°, which corresponds to the wetting properties of water on Poly(methyl methacrylate). The accuracy of the SPH simulations were validated against an analytical solution of Poiseuille flow between two parallel plates and against laboratory experiments. Using the SPH model, the complex flow mode transitions from droplet to rivulet flow of an experimental study were reproduced. Additionally, laboratory dimensionless scaling experiments of water droplets were successfully replicated in SPH. Finally, SPH simulations were used to investigate the partitioning dynamics of single droplets into synthetic horizontal fractures with various apertures (Δdf = 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 mm) and offsets (Δdoff = -1.5, -1.0, -0.5, 0, 1.0, 2.0, 3.0 mm). Fluid masses were measured in the domains R1, R2 and R3. The perfect conditions of ideally smooth surfaces and the SPH inherent advantage of particle tracking allow the recognition of small scale partitioning mechanisms and its importance for bulk flow behavior.

Assessing controls on perched saturated zones beneath the Idaho Nuclear Technology and Engineering Center, Idaho

USGS Publications Warehouse

Mirus, Benjamin B.; Perkins, Kim S.; Nimmo, John R.

2011-01-01

Waste byproducts associated with operations at the Idaho Nuclear Technology and Engineering Center (INTEC) have the potential to contaminate the eastern Snake River Plain (ESRP) aquifer. Recharge to the ESRP aquifer is controlled largely by the alternating stratigraphy of fractured volcanic rocks and sedimentary interbeds within the overlying vadose zone and by the availability of water at the surface. Beneath the INTEC facilities, localized zones of saturation perched on the sedimentary interbeds are of particular concern because they may facilitate accelerated transport of contaminants. The sources and timing of natural and anthropogenic recharge to the perched zones are poorly understood. Simple approaches for quantitative characterization of this complex, variably saturated flow system are needed to assess potential scenarios for contaminant transport under alternative remediation strategies. During 2009-2011, the U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, employed data analysis and numerical simulations with a recently developed model of preferential flow to evaluate the sources and quantity of recharge to the perched zones. Piezometer, tensiometer, temperature, precipitation, and stream-discharge data were analyzed, with particular focus on the possibility of contributions to the perched zones from snowmelt and flow in the neighboring Big Lost River (BLR). Analysis of the timing and magnitude of subsurface dynamics indicate that streamflow provides local recharge to the shallow, intermediate, and deep perched saturated zones within 150 m of the BLR; at greater distances from the BLR the influence of streamflow on recharge is unclear. Perched water-level dynamics in most wells analyzed are consistent with findings from previous geochemical analyses, which suggest that a combination of annual snowmelt and anthropogenic sources (for example, leaky pipes and drainage ditches) contribute to recharge of shallow and intermediate perched zones throughout much of INTEC. The source-responsive fluxes model was parameterized to simulate recharge via preferential flow associated with intermittent episodes of streamflow in the BLR. The simulations correspond reasonably well to the observed hydrologic response within the shallow perched zone. Good model performance indicates that source-responsive flow through a limited number of connected fractures contributes substantially to the perched-zone dynamics. The agreement between simulated and observed perched-zone dynamics suggest that the source-responsive fluxes model can provide a valuable tool for quantifying rapid preferential flow processes that may result from different land management scenarios.

Biomimetic wall-shaped hierarchical microstructure for gecko-like attachment.

PubMed

Kasem, Haytam; Tsipenyuk, Alexey; Varenberg, Michael

2015-04-21

Most biological hairy adhesive systems involved in locomotion rely on spatula-shaped terminal elements, whose operation has been actively studied during the last decade. However, though functional principles underlying their amazing performance are now well understood, due to technical difficulties in manufacturing the complex structure of hierarchical spatulate systems, a biomimetic surface structure featuring true shear-induced dynamic attachment still remains elusive. To try bridging this gap, a novel method of manufacturing gecko-like attachment surfaces is devised based on a laser-micromachining technology. This method overcomes the inherent disadvantages of photolithography techniques and opens wide perspectives for future production of gecko-like attachment systems. Advanced smart-performance surfaces featuring thin-film-based hierarchical shear-activated elements are fabricated and found capable of generating friction force of several tens of times the contact load, which makes a significant step forward towards a true gecko-like adhesive.

Dynamic protein coronas revealed as a modulator of silver nanoparticle sulphidation in vitro

NASA Astrophysics Data System (ADS)

Miclăuş, Teodora; Beer, Christiane; Chevallier, Jacques; Scavenius, Carsten; Bochenkov, Vladimir E.; Enghild, Jan J.; Sutherland, Duncan S.

2016-06-01

Proteins adsorbing at nanoparticles have been proposed as critical toxicity mediators and are included in ongoing efforts to develop predictive tools for safety assessment. Strongly attached proteins can be isolated, identified and correlated to changes in nanoparticle state, cellular association or toxicity. Weakly attached, rapidly exchanging proteins are also present at nanoparticles, but are difficult to isolate and have hardly been examined. Here we study rapidly exchanging proteins and show for the first time that they have a strong modulatory effect on the biotransformation of silver nanoparticles. Released silver ions, known for their role in particle toxicity, are found to be trapped as silver sulphide nanocrystals within the protein corona at silver nanoparticles in serum-containing cell culture media. The strongly attached corona acts as a site for sulphidation, while the weakly attached proteins reduce nanocrystal formation in a serum-concentration-dependent manner. Sulphidation results in decreased toxicity of Ag NPs.

Vibrational excitation and dissociative attachment of a triatomic molecule: CO/sub 2/ in the collinear approximation

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

Wong, C.F.; Light, J.C.

1986-02-01

The effective R-matrix model and the R-matrix propagative method applied earlier to elec- tron--diatomic-molecule scattering are extended to treat dissociative attachment of collinear triatomic molecules. To describe the vibrational excitation and dissociative attachment of CO/sub 2/ in the 4-eV region, the nuclear dynamics is solved on a Wall-Porter potential-energy surface. A hybrid approach is developed in which the L/sup 2/ and R-matrix propagation methods are combined to evaluate the global R matrix. Our calculations show that it is easier to excite the symmetric mode vibrations than the asymmetric mode vibrations. Our results also show that the observed structures in themore » energy dependence of the dissociative attachment cross sections are due to the vibrational states of the negative ion (CO/sub 2/ /sup -/) and not to the vibrational states of the CO fragment.« less

Rare reaction channels in real-time time-dependent density functional theory: the test case of electron attachment

NASA Astrophysics Data System (ADS)

Lacombe, Lionel; Dinh, P. Huong Mai; Reinhard, Paul-Gerhard; Suraud, Eric; Sanche, Leon

2015-08-01

We present an extension of standard time-dependent density functional theory (TDDFT) to include the evaluation of rare reaction channels, taking as an example of application the theoretical modelling of electron attachment to molecules. The latter process is of great importance in radiation-induced damage of biological tissue for which dissociative electron attachment plays a decisive role. As the attachment probability is very low, it cannot be extracted from the TDDFT propagation whose mean field provides an average over various reaction channels. To extract rare events, we augment TDDFT by a perturbative treatment to account for the occasional jumps, namely electron capture in our test case. We apply the modelling to electron attachment to H2O, H3O+, and (H2O)2. Dynamical calculations have been done at low energy (3-16 eV). We explore, in particular, how core-excited states of the targets show up as resonances in the attachment probability. Contribution to the Topical Issue "COST Action Nano-IBCT: Nano-scale Processes Behind Ion-Beam Cancer Therapy", edited by Andrey Solov'yov, Nigel Mason, Gustavo García, Eugene Surdutovich.

Asymmetrical development of root endodermis and exodermis in reaction to abiotic stresses

PubMed Central

Líška, Denis; Martinka, Michal; Kohanová, Jana; Lux, Alexander

2016-01-01

Background and Aims In the present study, we show that development of endodermis and exodermis is sensitively regulated by water accessibility. As cadmium (Cd) is known to induce xeromorphic effects in plants, maize roots were exposed also to Cd to understand the developmental process of suberin lamella deposition in response to a local Cd source. Methods In a first experiment, maize roots were cultivated in vitro and unilaterally exposed to water-containing medium from one side and to air from the other. In a second experiment, the roots were placed between two agar medium layers with a strip of Cd-containing medium attached locally and unilaterally to the root surface. Key Results The development of suberin lamella (the second stage of exodermal and endodermal development) started asymmetrically, preferentially closer to the root tip on the side exposed to the air. In the root contact with Cd in a spatially limited area exposed to one side of the root, suberin lamella was preferentially developed in the contact region and additionally along the whole length of the root basipetally from the contact area. However, the development was unilateral and asymmetrical, facing the treated side. The same pattern occurred irrespective of the distance of Cd application from the root apex. Conclusions These developmental characteristics indicate a sensitive response of root endodermis and exodermis in the protection of vascular tissues against abiotic stresses. PMID:27112163

Dynamics of solvation and desolvation of rubidium attached to He nanodroplets

NASA Astrophysics Data System (ADS)

von Vangerow, J.; John, O.; Stienkemeier, F.; Mudrich, M.

2015-07-01

The real-time dynamics of photoexcited and photoionized rubidium (Rb) atoms attached to helium (He) nanodroplets is studied by femtosecond pump-probe mass spectrometry. While excited Rb atoms in the perturbed 6p-state (Rb*) desorb off the He droplets, Rb+ photoions tend to sink into the droplet interior when created near the droplet surface. The transition from Rb+ solvation to full Rb* desorption is found to occur at a delay time τ ˜ 600 fs for Rb* in the 6pΣ-state and τ ˜ 1200 fs for the 6pΠ-state. Rb+He ions are found to be created by directly exciting bound Rb*He exciplex states as well as by populating bound Rb+He-states in a photoassociative ionization process.

Monoclonal Antibodies Attached to Carbon Nanotube Transistors for Paclitaxel Detection

NASA Astrophysics Data System (ADS)

Lee, Wonbae; Lau, Calvin; Richardson, Mark; Rajapakse, Arith; Weiss, Gregory; Collins, Philip; UCI, Molecular Biology; Biochemistry Collaboration; UCI, Departments of Physics; Astronomy Collaboration

Paclitaxel is a naturally-occurring pharmaceutical used in numerous cancer treatments, despite its toxic side effects. Partial inhibition of this toxicity has been demonstrated using weakly interacting monoclonal antibodies (3C6 and 8A10), but accurate monitoring of antibody and paclitaxel concentrations remains challenging. Here, single-molecule studies of the kinetics of antibody-paclitaxel interactions have been performed using single-walled carbon nanotube field-effect transistors. The devices were sensitized with single antibody attachments to record the single-molecule binding dynamics of paclitaxel. This label-free technique recorded a range of dynamic interactions between the antibody and paclitaxel, and it provided sensitive paclitaxel detection for pM to nM concentrations. Measurements with two different antibodies suggest ways of extending this working range and uncovering the mechanistic differences among different antibodies.

Coalescence preference and droplet size inequality during fluid phase segregation

NASA Astrophysics Data System (ADS)

Roy, Sutapa

2018-02-01

Using molecular dynamics simulations and scaling arguments, we investigate the coalescence preference dynamics of liquid droplets in a phase-segregating off-critical, single-component fluid. It is observed that the preferential distance of the product drop from its larger parent, during a coalescence event, gets smaller for large parent size inequality. The relative coalescence position exhibits a power-law dependence on the parent size ratio with an exponent q ≃ 3.1 . This value of q is in strong contrast with earlier reports 2.1 and 5.1 in the literature. The dissimilarity is explained by considering the underlying coalescence mechanisms.

Hand-pumps as reservoirs for microbial contamination of well water

PubMed Central

Ferguson, Andrew S.; Mailloux, Brian J.; Ahmed, Kazi M.; van Geen, Alexander; McKay, Larry D.; Culligan, Patricia J.

2018-01-01

The retention and release of total coliforms and Escherichia coli was investigated in hand-pumps removed from tubewells tapping a faecally contaminated aquifer in Matlab, Bangladesh, and from a new hand-pump deliberately spiked with E. coli. All hand-pumps were connected to reservoirs of sterile water and flushed. Faecal coliforms were observed in the discharge from all three of the previously used hand-pumps, at concentrations comparable to levels measured in discharge when they were attached to the tubewells. During daily flushing of one of the previously used hand-pumps, the concentration of total coliforms in the discharge remained relatively constant (≈103 MPN/100 mL). Concentrations of E. coli in the pump discharge declined over time, but E. coli was still detectable up to 29 days after the start of flushing. In the deliberately spiked hand-pump, E. coli was observed in the discharge over 125 days (t50 = 8 days) and found to attach preferentially to elastomeric materials within the hand-pump. Attempts to disinfect both the village and new hand-pumps using shock chlorination were shown to be unsuccessful. These results demonstrate that hand-pumps can act as persistent reservoirs for microbial indicator bacteria. This could potentially influence drinking water quality and bias testing of water quality. PMID:22048430

Analysis of the isomer ratios of polymethylated-DOTA complexes and the implications on protein structural studies

PubMed Central

Opina, Ana Christina L.; Strickland, Madeleine; Lee, Yong-Sok; Tjandra, Nico; Byrd, R. Andrew; Swenson, Rolf E.; Vasalatiy, Olga

2016-01-01

A rigidified and symmetrical polymethylated 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) ligand bearing four SSSS methyl groups in both the tetraaza ring and the acetate arms (SSSS-SSSS-M4DOTMA) was prepared. The isomer ratio of SSSS-SSSS-M4DOTMA complexed with a series of lanthanide ions was carefully investigated using RP-HPLC and NMR. A square antiprismatic (SAP) configuration was exclusively observed for the early lanthanides, while the twisted square antiprismatic (TSAP) geometry was preferred as the lanthanide ion size decreases. The late lanthanides preferentially adopted the TSAP geometry. One of the pendant arms was modified with a pyridyl disulfide group (SSSS-SSSS-M8SPy) for cysteine attachment and displayed a similar isomer trend as the parent compound, Ln-SSSS-SSSS-M4DOTMA. Covalent attachment to the ubiquitin S57C mutant showed resonances whose intensities are in agreement with the isomeric population observed by HPLC. Furthermore, the NOE experiments combined with quantum chemical calculations have unequivocally demonstrated that the SAP of Pr-SSSS-SSSS-M4DOTMA and Pr-SSSS-SSSS-M8SPy, as well as the TSAP of Yb-SSSS-SSSS-M8SPy are more stable than their corresponding isomers. PMID:26857249

Molecular dynamics study of ionic liquid confined in silicon nanopore

NASA Astrophysics Data System (ADS)

Liu, Y. S.; Sha, M. L.; Cai, K. Y.

2017-05-01

Molecular dynamics simulations was carried to investigate the structure and dynamics of [BMIM][PF6] ionic liquid (IL) confined inside a slit-like silicon nanopore with pore size of 5.5 nm. It is clearly shown that the mass and number densities of the confined ILs are oscillatory, high density layers are also formed in the vicinity of the silicon surface, which indicates the existence of solid-like high density IL layers. The orientational investigation shows that the imidazolium ring of [BMIM] cation lies preferentially flat on the surface of the silicon pore walls. Furthermore, the mean squared displacement (MSD) calculation indicates that the dynamics of confined ILs are significantly slower than those observed in bulk systems. Our results suggest that the interactions between the pore walls and the ILs can strongly affect the structural and dynamical properties of the confined ILs.

Information filtering via preferential diffusion.

PubMed

Lü, Linyuan; Liu, Weiping

2011-06-01

Recommender systems have shown great potential in addressing the information overload problem, namely helping users in finding interesting and relevant objects within a huge information space. Some physical dynamics, including the heat conduction process and mass or energy diffusion on networks, have recently found applications in personalized recommendation. Most of the previous studies focus overwhelmingly on recommendation accuracy as the only important factor, while overlooking the significance of diversity and novelty that indeed provide the vitality of the system. In this paper, we propose a recommendation algorithm based on the preferential diffusion process on a user-object bipartite network. Numerical analyses on two benchmark data sets, MovieLens and Netflix, indicate that our method outperforms the state-of-the-art methods. Specifically, it can not only provide more accurate recommendations, but also generate more diverse and novel recommendations by accurately recommending unpopular objects.

Information filtering via preferential diffusion

NASA Astrophysics Data System (ADS)

Lü, Linyuan; Liu, Weiping

2011-06-01

Recommender systems have shown great potential in addressing the information overload problem, namely helping users in finding interesting and relevant objects within a huge information space. Some physical dynamics, including the heat conduction process and mass or energy diffusion on networks, have recently found applications in personalized recommendation. Most of the previous studies focus overwhelmingly on recommendation accuracy as the only important factor, while overlooking the significance of diversity and novelty that indeed provide the vitality of the system. In this paper, we propose a recommendation algorithm based on the preferential diffusion process on a user-object bipartite network. Numerical analyses on two benchmark data sets, MovieLens and Netflix, indicate that our method outperforms the state-of-the-art methods. Specifically, it can not only provide more accurate recommendations, but also generate more diverse and novel recommendations by accurately recommending unpopular objects.

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

Vermaas, Josh V.; Petridis, Loukas; Qi, Xianghong

The conversion of plant biomass to ethanol via enzymatic cellulose hydrolysis offers a potentially sustainable route to biofuel production. However, the inhibition of enzymatic activity in pretreated biomass by lignin severely limits the efficiency of this process. By performing atomic-detail molecular dynamics simulation of a biomass model containing cellulose, lignin, and cellulases (TrCel7A), we elucidate detailed lignin inhibition mechanisms. We find that lignin binds preferentially both to the elements of cellulose to which the cellulases also preferentially bind (the hydrophobic faces) and also to the specific residues on the cellulose-binding module of the cellulase that are critical for cellulose bindingmore » of TrCel7A (Y466, Y492, and Y493). In conclusion, lignin thus binds exactly where for industrial purposes it is least desired, providing a simple explanation of why hydrolysis yields increase with lignin removal.« less

Analysis of the effects of firing Orbiter primary reaction control system jets with an attached truss structure

NASA Technical Reports Server (NTRS)

Kaszubowski, M.; Raney, J. P.

1986-01-01

A study was conducted to determine the dynamic effects of firing the orbiter primary reaction control jets during assembly of protoflight space station structure. Maximum longeron compressive load was calculated as a function of jet pulse time length, number of jet pulses, and total torque imposed by the reaction control jets. The study shows that it is possible to fire selected jets to achieve a pitch maneuver without causing failure of the attached structure.

Experience versus talent shapes the structure of the Web

PubMed Central

Kong, Joseph S.; Sarshar, Nima; Roychowdhury, Vwani P.

2008-01-01

We use sequential large-scale crawl data to empirically investigate and validate the dynamics that underlie the evolution of the structure of the web. We find that the overall structure of the web is defined by an intricate interplay between experience or entitlement of the pages (as measured by the number of inbound hyperlinks a page already has), inherent talent or fitness of the pages (as measured by the likelihood that someone visiting the page would give a hyperlink to it), and the continual high rates of birth and death of pages on the web. We find that the web is conservative in judging talent and the overall fitness distribution is exponential, showing low variability. The small variance in talent, however, is enough to lead to experience distributions with high variance: The preferential attachment mechanism amplifies these small biases and leads to heavy-tailed power-law (PL) inbound degree distributions over all pages, as well as over pages that are of the same age. The balancing act between experience and talent on the web allows newly introduced pages with novel and interesting content to grow quickly and surpass older pages. In this regard, it is much like what we observe in high-mobility and meritocratic societies: People with entitlement continue to have access to the best resources, but there is just enough screening for fitness that allows for talented winners to emerge and join the ranks of the leaders. Finally, we show that the fitness estimates have potential practical applications in ranking query results. PMID:18779560

Binding Preferences, Surface Attachment, Diffusivity, and Orientation of a Family 1 Carbohydrate-binding Module on Cellulose*

PubMed Central

Nimlos, Mark R.; Beckham, Gregg T.; Matthews, James F.; Bu, Lintao; Himmel, Michael E.; Crowley, Michael F.

2012-01-01

Cellulase enzymes often contain carbohydrate-binding modules (CBMs) for binding to cellulose. The mechanisms by which CBMs recognize specific surfaces of cellulose and aid in deconstruction are essential to understand cellulase action. The Family 1 CBM from the Trichoderma reesei Family 7 cellobiohydrolase, Cel7A, is known to selectively bind to hydrophobic surfaces of native cellulose. It is most commonly suggested that three aromatic residues identify the planar binding face of this CBM, but several recent studies have challenged this hypothesis. Here, we use molecular simulation to study the CBM binding orientation and affinity on hydrophilic and hydrophobic cellulose surfaces. Roughly 43 μs of molecular dynamics simulations were conducted, which enables statistically significant observations. We quantify the fractions of the CBMs that detach from crystal surfaces or diffuse to other surfaces, the diffusivity along the hydrophobic surface, and the overall orientation of the CBM on both hydrophobic and hydrophilic faces. The simulations demonstrate that there is a thermodynamic driving force for the Cel7A CBM to bind preferentially to the hydrophobic surface of cellulose relative to hydrophilic surfaces. In addition, the simulations demonstrate that the CBM can diffuse from hydrophilic surfaces to the hydrophobic surface, whereas the reverse transition is not observed. Lastly, our simulations suggest that the flat faces of Family 1 CBMs are the preferred binding surfaces. These results enhance our understanding of how Family 1 CBMs interact with and recognize specific cellulose surfaces and provide insights into the initial events of cellulase adsorption and diffusion on cellulose. PMID:22496371

Complex nonlinear dynamics in the limit of weak coupling of a system of microcantilevers connected by a geometrically nonlinear tunable nanomembrane.

PubMed

Jeong, Bongwon; Cho, Hanna; Keum, Hohyun; Kim, Seok; Michael McFarland, D; Bergman, Lawrence A; King, William P; Vakakis, Alexander F

2014-11-21

Intentional utilization of geometric nonlinearity in micro/nanomechanical resonators provides a breakthrough to overcome the narrow bandwidth limitation of linear dynamic systems. In past works, implementation of intentional geometric nonlinearity to an otherwise linear nano/micromechanical resonator has been successfully achieved by local modification of the system through nonlinear attachments of nanoscale size, such as nanotubes and nanowires. However, the conventional fabrication method involving manual integration of nanoscale components produced a low yield rate in these systems. In the present work, we employed a transfer-printing assembly technique to reliably integrate a silicon nanomembrane as a nonlinear coupling component onto a linear dynamic system with two discrete microcantilevers. The dynamics of the developed system was modeled analytically and investigated experimentally as the coupling strength was finely tuned via FIB post-processing. The transition from the linear to the nonlinear dynamic regime with gradual change in the coupling strength was experimentally studied. In addition, we observed for the weakly coupled system that oscillation was asynchronous in the vicinity of the resonance, thus exhibiting a nonlinear complex mode. We conjectured that the emergence of this nonlinear complex mode could be attributed to the nonlinear damping arising from the attached nanomembrane.

Silver Nanocube and Nanobar Growth via Anisotropic Monomer Addition and Particle Attachment Processes

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

Xiao, Dongdong; Wu, Zhigang; Song, Miao

Understanding the growth mechanism of noble metal nanocrystals during solution synthesis is of significant importance for shape and property control. However, much remains unknown about the growth pathways of metal nanoparticles due to lack of direct observation. Using an in-situ transmission electron microscopy technique, we directly observed Ag nanocube and nanobar growth in aqueous solution through both classical monomer-by-monomer addition and non-classical particle attachment processes. During the particle attachment process, Ag nanocubes and nanobars formed via both oriented and non-oriented attachment. Our calculations, along with dynamics of the observed attachment, showed that van der Waals force overcame hydrodynamic and frictionmore » forces and drove the particles toward each other. During classical growth, an anisotropic growth was also revealed, and the resulting unsymmetrical shape constituted an intermediate state for Ag nanocube growth. We hypothesized that the temporary symmetry breaking resulted from different growth rates on {001} surfaces due to a local surface concentration variation caused by the imbalance between the consumption of Ag+ near the surface and the diffusion of Ag+ from bulk to surface.« less

The development and evaluation of a community attachment scheme for first-year medical students.

PubMed

Hannay, David; Mitchell, Caroline; Chung, Man Cheung

2003-03-01

This paper describes the development over 14 years of a Community Attachment Scheme for First Year Medical Students in Sheffield, together with feedback from tutors and students. The scheme involves pairs of students visiting families expecting a baby or experiencing an illness. The families are identified by general practitioners who act as tutors together with a behavioural scientist for groups of eight to 10 students. The scheme provides first-year students with practical experience of sociology and psychology in terms of family dynamics and illness behaviour. Assessment is part of the degree examination, and involves a written assignment on the family, together with tutors' assessments. The development of the attachment scheme took place in three phases, which are described together with feedback from tutors and students, as well as changes in methods of assessment. The basis of the Community Attachment Scheme has been self-directed problem-based learning in small groups with continuous assessment, and these principles have now extended to the rest of the medical curriculum in Sheffield, of which the Community Attachment Scheme is an integral part.

Modeling Aggregation Processes of Lennard-Jones particles Via Stochastic Networks

NASA Astrophysics Data System (ADS)

Forman, Yakir; Cameron, Maria

2017-07-01

We model an isothermal aggregation process of particles/atoms interacting according to the Lennard-Jones pair potential by mapping the energy landscapes of each cluster size N onto stochastic networks, computing transition probabilities from the network for an N-particle cluster to the one for N+1, and connecting these networks into a single joint network. The attachment rate is a control parameter. The resulting network representing the aggregation of up to 14 particles contains 6427 vertices. It is not only time-irreversible but also reducible. To analyze its transient dynamics, we introduce the sequence of the expected initial and pre-attachment distributions and compute them for a wide range of attachment rates and three values of temperature. As a result, we find the configurations most likely to be observed in the process of aggregation for each cluster size. We examine the attachment process and conduct a structural analysis of the sets of local energy minima for every cluster size. We show that both processes taking place in the network, attachment and relaxation, lead to the dominance of icosahedral packing in small (up to 14 atom) clusters.

Actin-filament disassembly: it takes two to shrink them fast.

PubMed

Winterhoff, Moritz; Faix, Jan

2015-06-01

Actin-filament disassembly is indispensable for replenishing the pool of polymerizable actin and allows continuous dynamic remodelling of the actin cytoskeleton. A new study now reveals that ADF/cofilin preferentially dismantles branched networks and provides new insights into the collaborative work of ADF/cofilin and Aip1 on filament disassembly at the molecular level. Copyright © 2015 Elsevier Ltd. All rights reserved.

Vadose zone dynamics governing snowmelt infiltration and groundwater recharge in a seasonally frozen, semi-arid landscape

NASA Astrophysics Data System (ADS)

Mohammed, A.; LeBlanc, F.; Cey, E. E.; Hayashi, M.

2016-12-01

Snowmelt infiltration and vadose zone fluxes in seasonally frozen soils are strongly affected by meteorological and soil moisture dynamics occurring during the preceding fall and winter, and complex processes controlling soil hydraulic and thermal regimes. In order to predict their effects on hydrologic processes such as run-off generation, groundwater recharge and plant-water availability in cold regions, an improved understanding of the mechanisms governing coupled water and heat fluxes in the unsaturated zone is needed. Field and laboratory studies were conducted to investigate snowmelt infiltration and groundwater recharge through partially frozen ground over a range of climate and soil conditions in the Canadian Prairies. Meteorological and subsurface field measurements at three sites were combined with laboratory infiltration experiments on frozen undisturbed soil-columns to provide insights into the hydraulic and thermal processes governing water movement. Analysis reveals that antecedent moisture content and thermal profiles both strongly affect subsurface dynamics during infiltration of snowmelt. Preferential flow is also a critical parameter, as both thermal and hydraulic responses were observed at depth prior to complete ground thaw in the field; as well as drainage outflow from the frozen soil column experiments under certain conditions. Results indicate that both diffuse (matrix) and preferential (macropore) flow play significant roles in the infiltration and redistribution of snowmelt water under frozen soil conditions, and shallow groundwater recharge. This study highlights the critical subsurface factors and processes that control infiltration and groundwater recharge in these seasonally frozen landscapes.

A novel physical eco-hydrological model concept for preferential flow based on experimental applications.

NASA Astrophysics Data System (ADS)

Jackisch, Conrad; van Schaik, Loes; Graeff, Thomas; Zehe, Erwin

2014-05-01

Preferential flow through macropores often determines hydrological characteristics - especially regarding runoff generation and fast transport of solutes. Macropore settings may yet be very different in nature and dynamics, depending on their origin. While biogenic structures follow activity cycles (e.g. earth worms) and population conditions (e.g. roots), pedogenic and geogenic structures may depend on water stress (e.g. cracks) or large events (e.g. flushed voids between skeleton and soil pipes) or simply persist (e.g. bedrock interface). On the one hand, such dynamic site characteristics can be observed in seasonal changes in its reaction to precipitation. On the other hand, sprinkling experiments accompanied by tracers or time-lapse 3D Ground-Penetrating-Radar are suitable tools to determine infiltration patterns and macropore configuration. However, model representation of the macropore-matrix system is still problematic, because models either rely on effective parameters (assuming well-mixed state) or on explicit advection strongly simplifying or neglecting interaction with the diffusive flow domain. Motivated by the dynamic nature of macropores, we present a novel model approach for interacting diffusive and advective water, solutes and energy transport in structured soils. It solely relies on scale- and process-aware observables. A representative set of macropores (data from sprinkling experiments) determines the process model scale through 1D advective domains. These are connected to a 2D matrix domain which is defined by pedo-physical retention properties. Water is represented as particles. Diffusive flow is governed by a 2D random walk of these particles while advection may take place in the macropore domain. Macropore-matrix interaction is computed as dissipation of the advective momentum of a particle by its experienced drag from the matrix domain. Through a representation of matrix and macropores as connected diffusive and advective domains for water transport we open up double domain concepts linking porescale physics to preferential macroscale fingerprints without effective parameterisation or mixing assumptions. Moreover, solute transport, energy balance aspects and lateral heterogeneity in soil moisture distribution are intrinsically captured. In addition, macropore and matrix domain settings may change over time based on physical and stochastic observations. The representativity concept allows scaleability from plotscale to the lower mesoscale.

Mineralogical controls on surface colonization by sulfur-metabolizing microbial communities

NASA Astrophysics Data System (ADS)

Jones, A. A.; Bennett, P.

2012-12-01

When characterizing microbial diversity and the microbial ecosystem of the shallow subsurface the mineral matrix is generally assumed to be homogenous and unreactive. We report here experimental evidence that microorganisms colonize rock surfaces according to the rock's chemistry and the organism's metabolic requirements and tolerances. We investigated this phenomenon using laboratory biofilm reactors with both a pure culture of sulfur-oxidizing Thiothrix unzii and a mixed environmental sulfur-metabolizing community from Lower Kane, Cave, WY, USA. Reactors contained rock and mineral chips (calcite, albite, microcline, quartz, chert, Madison Limestone (ML), Madison Dolostone (MD), and basalt) amended with one of the two inoculants. Biomass of attached microorganisms on each mineral surface was quantified. The 16S rRNA of attached microbial communities were compared using Roche FLX and Titanium 454 next generation pyrosequencing. A primary controlling factor on taxonomy of attached microorganisms in both pure and mixed culture experiments was mineral buffering capacity. In mixed culture experiments acid-buffering carbonates were preferentially colonized by neutrophilic sulfur-oxidizing microorganisms (~18% to ~27% of microorganisms), while acidophilic sulfur-oxidizing microorganisms colonized non-buffering quartz exclusively (~46% of microorganisms). The nutrient content of the rock was a controlling factor on biomass accumulation, with neutrophilic organisms selecting between carbonate surfaces of equivalent buffer capacities according to the availability of phosphate. Dry biomass on ML was 17.8 ± 2.3 mg/cm2 and MD was 20.6 ± 6.8 mg/cm2; while nutrient poor calcite accumulated 2.4 ± 0.3 mg/cm2. Biomass accumulation was minimal on non-buffering nutrient-limited surfaces. These factors are countered by the competitive exclusion of some populations. A pure culture of T. unzii preferentially colonizes carbonates while a very closely related Thiothrix spp is excluded from these same rock samples in a mixed culture. Diversity analysis reveals that ML, MD, and calcite have >98% of sequences belonging to shared OTUs. The carbonates have <3% of sequences belonging to OTUs shared with any silicate mineral surface with the exception of basalt (~85% similarity). These four surfaces were host to the least diverse microbial communities, suggesting that competitive exclusion of microorganisms not adapted to these surfaces is a controlling variable on taxonomy. Furthermore, the microorganisms on basalt reveal an unique association between Thiothrix unzii (often found in mid-ocean ridge environments) and basalt, where it excludes other sulfur oxidizers and accumulates the highest non-carbonate biomass in both pure (3.5 ± 1.0 mg/cm2) and mixed culture (5.4 ± 1.4 mg/cm2) experiments. This association suggests that adaptations to specific rocks may be retained even when the organism is displaced from an ancestral rock/mineral surface habitat. Combined, these variables (buffering capacity, nutrient availability, competitive exclusion, tolerance of surface geochemistry, and latent adaptations) affect biomass density, local diversity, and global diversity of the attached communities on mineral and rock surfaces and suggest that different populations are more tolerant of, and more competitive on, specific rock/mineral types.

Developmental processes across the first two years of parenthood: Stability and change in adult attachment style.

PubMed

Stern, Jessica A; Fraley, R Chris; Jones, Jason D; Gross, Jacquelyn T; Shaver, Phillip R; Cassidy, Jude

2018-05-01

The first months after becoming a new parent are a unique and important period in human development. Despite substantial research on the many social and biological changes that occur during the first months of parenthood, little is known about changes in mothers' attachment. The present study examines developmental stability and change in first-time mothers' attachment style across the first 2 years of motherhood. At Time 1, 162 economically stressed primiparous mothers (Mage = 23.98 years, SD = 5.18) completed measures of attachment anxiety and avoidance at five time points: when their children were 0, 6, 12, 18, and 24 months of age. Converging results of stability functions and latent growth curve models suggest that attachment styles were generally stable during the first 2 years of motherhood, even in this economically stressed sample. Furthermore, model comparisons revealed that a prototype model better characterized the developmental dynamics of mothers' attachment style than did a revisionist model, consistent with previous studies of adults and adolescents. This suggests that a relatively enduring prototype underlies mothers' attachment style and anchors the extent to which mothers experience attachment-related changes following the birth of their first child. Within this overall picture of continuity, however, some mothers did show change over time, and specific factors emerged as moderators of attachment stability, including maternal depressive symptoms and overall psychological distress, as well as sensitive care from their own mothers. Findings shed light on patterns of continuity and change in new parents' development. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Tethered particle analysis of supercoiled circular DNA using peptide nucleic acid handles.

PubMed

Norregaard, Kamilla; Andersson, Magnus; Nielsen, Peter Eigil; Brown, Stanley; Oddershede, Lene B

2014-09-01

This protocol describes how to monitor individual naturally supercoiled circular DNA plasmids bound via peptide nucleic acid (PNA) handles between a bead and a surface. The protocol was developed for single-molecule investigation of the dynamics of supercoiled DNA, and it allows the investigation of both the dynamics of the molecule itself and of its interactions with a regulatory protein. Two bis-PNA clamps designed to bind with extremely high affinity to predetermined homopurine sequence sites in supercoiled DNA are prepared: one conjugated with digoxigenin for attachment to an anti-digoxigenin-coated glass cover slide, and one conjugated with biotin for attachment to a submicron-sized streptavidin-coated polystyrene bead. Plasmids are constructed, purified and incubated with the PNA handles. The dynamics of the construct is analyzed by tracking the tethered bead using video microscopy: less supercoiling results in more movement, and more supercoiling results in less movement. In contrast to other single-molecule methodologies, the current methodology allows for studying DNA in its naturally supercoiled state with constant linking number and constant writhe. The protocol has potential for use in studying the influence of supercoils on the dynamics of DNA and its associated proteins, e.g., topoisomerase. The procedure takes ~4 weeks.

CENP-E Kinesin Interacts with SKAP Protein to Orchestrate Accurate Chromosome Segregation in Mitosis*

PubMed Central

Huang, Yuejia; Wang, Wenwen; Yao, Phil; Wang, Xiwei; Liu, Xing; Zhuang, Xiaoxuan; Yan, Feng; Zhou, Jinhua; Du, Jian; Ward, Tarsha; Zou, Hanfa; Zhang, Jiancun; Fang, Guowei; Ding, Xia; Dou, Zhen; Yao, Xuebiao

2012-01-01

Mitotic chromosome segregation is orchestrated by the dynamic interaction of spindle microtubules with the kinetochore. Although previous studies show that the mitotic kinesin CENP-E forms a link between attachment of the spindle microtubule to the kinetochore and the mitotic checkpoint signaling cascade, the molecular mechanism underlying dynamic kinetochore-microtubule interactions in mammalian cells remains elusive. Here, we identify a novel interaction between CENP-E and SKAP that functions synergistically in governing dynamic kinetochore-microtubule interactions. SKAP binds to the C-terminal tail of CENP-E in vitro and is essential for an accurate kinetochore-microtubule attachment in vivo. Immunoelectron microscopic analysis indicates that SKAP is a constituent of the kinetochore corona fibers of mammalian centromeres. Depletion of SKAP or CENP-E by RNA interference results in a dramatic reduction of inter-kinetochore tension, which causes chromosome mis-segregation with a prolonged delay in achieving metaphase alignment. Importantly, SKAP binds to microtubules in vitro, and this interaction is synergized by CENP-E. Based on these findings, we propose that SKAP cooperates with CENP-E to orchestrate dynamic kinetochore-microtubule interaction for faithful chromosome segregation. PMID:22110139

Internal and external atomic steps in graphite exhibit dramatically different physical and chemical properties.

PubMed

Lee, Hyunsoo; Lee, Han-Bo-Ram; Kwon, Sangku; Salmeron, Miquel; Park, Jeong Young

2015-04-28

We report on the physical and chemical properties of atomic steps on the surface of highly oriented pyrolytic graphite (HOPG) investigated using atomic force microscopy. Two types of step edges are identified: internal (formed during crystal growth) and external (formed by mechanical cleavage of bulk HOPG). The external steps exhibit higher friction than the internal steps due to the broken bonds of the exposed edge C atoms, while carbon atoms in the internal steps are not exposed. The reactivity of the atomic steps is manifested in a variety of ways, including the preferential attachment of Pt nanoparticles deposited on HOPG when using atomic layer deposition and KOH clusters formed during drop casting from aqueous solutions. These phenomena imply that only external atomic steps can be used for selective electrodeposition for nanoscale electronic devices.

Strain Sensors, Methods of Making Same, and Applications of Same

NASA Technical Reports Server (NTRS)

Hatfield, Walter (Inventor); Biris, Alexandru S. (Inventor); Trigwell, Steven (Inventor)

2015-01-01

In one aspect, the present invention relates to a layered structure usable in a strain sensor. In one embodiment, the layered structure has a substrate with a first surface and an opposite, second surface defining a body portion therebetween; and a film of carbon nanotubes deposited on the first surface of the substrate, wherein the film of carbon nanotubes is conductive and characterized with an electrical resistance. In one embodiment, the carbon nanotubes are aligned in a preferential direction. In one embodiment, the carbon nanotubes are formed in a yarn such that any mechanical stress increases their electrical response. In one embodiment, the carbon nanotubes are incorporated into a polymeric scaffold that is attached to the surface of the substrate. In one embodiment, the surfaces of the carbon nanotubes are functionalized such that its electrical conductivity is increased.

Strain sensors, methods of making same, and applications of same

DOEpatents

Biris, Alexandru S.; Trigwell, Steven; Hatfield, Walter

2015-06-30

In one aspect, the present invention relates to a layered structure usable in a strain sensor. In one embodiment, the layered structure has a substrate with a first surface and an opposite, second surface defining a body portion therebetween; and a film of carbon nanotubes deposited on the first surface of the substrate, wherein the film of carbon nanotubes is conductive and characterized with an electrical resistance. In one embodiment, the carbon nanotubes are aligned in a preferential direction. In one embodiment, the carbon nanotubes are formed in a yarn such that any mechanical stress increases their electrical response. In one embodiment, the carbon nanotubes are incorporated into a polymeric scaffold that is attached to the surface of the substrate. In one embodiment, the surfaces of the carbon nanotubes are functionalized such that its electrical conductivity is increased.

Self-assembly of vertically aligned quantum ring-dot structure by Multiple Droplet Epitaxy

NASA Astrophysics Data System (ADS)

Elborg, Martin; Noda, Takeshi; Mano, Takaaki; Kuroda, Takashi; Yao, Yuanzhao; Sakuma, Yoshiki; Sakoda, Kazuaki

2017-11-01

We successfully grow vertically aligned quantum ring-dot structures by Multiple Droplet Epitaxy technique. The growth is achieved by depositing GaAs quantum rings in a first droplet epitaxy process which are subsequently covered by a thin AlGaAs barrier. In a second droplet epitaxy process, Ga droplets preferentially position in the center indentation of the ring as well as attached to the edge of the ring in [ 1 1 bar 0 ] direction. By designing the ring geometry, full selectivity for the center position of the ring is achieved where we crystallize the droplets into quantum dots. The geometry of the ring and dot as well as barrier layer can be controlled in separate growth steps. This technique offers great potential for creating complex quantum molecules for novel quantum information technologies.

“A child’s nightmare. Mum comes and comforts her child.” Attachment evaluation as a guide in the assessment and treatment in a clinical case study

PubMed Central

Salcuni, Silvia; Di Riso, Daniela; Lis, Adriana

2014-01-01

There is a gap between proposed theoretical attachment theory frameworks, measures of attachment in the assessment phase and their relationship with changes in outcome after a psychodynamic oriented psychotherapy. Based on a clinical case study of a young woman with Panic Attack Disorder, this paper examined psychotherapy outcome findings comparing initial and post-treatment assessments, according to the mental functioning in S and M-axis of the psychodynamic diagnostic manual. Treatment planning and post-treatment changes were described with the main aim to illustrate from a clinical point of view why a psycho-dynamic approach, with specific attention to an “attachment theory stance,” was considered the treatment of choice for this patient. The Symptom Check List 90 Revised (SCL-90-R) and the Shedler–Westen Assessment Procedure (SWAP–200) were administered to detect patient’s symptomatic perception and clinician’s diagnostic points of view, respectively; the Adult Attachment Interview and the Adult Attachment Projective Picture System (AAP) were also administered as to pay attention to patient’s unconscious internal organization and changes in defense processes. A qualitative description of how the treatment unfolded was included. Findings highlight the important contribution of attachment theory in a 22-month psychodynamic psychotherapy framework, promoting resolution of patient’s symptoms and adjustment. PMID:25191293

Autism, attachment, and social learning: Three challenges and a way forward.

PubMed

Vivanti, Giacomo; Nuske, Heather J

2017-05-15

We explore three challenges that Autism Spectrum Disorder (ASD) poses to our understanding of the processes underlying early attachment. First, while caregiver-infant attachment and later social-affiliative behavior share common biobehavioral mechanisms, individuals with ASD are able to form secure attachment relationships, despite reduced social-emotional reciprocity and motivation for social interaction. Therefore, disruptions in social affiliation mechanisms can co-exist with secure caregiver-infant bonding. Second, while early attachment quality is associated with later social outcomes in typical development, interventions targeting caregiver-child interaction in ASD often show positive effects on parental responsivity and attachment quality, but not on child social behavior. Therefore, improvements in parent-child bonding do not necessarily result in improvements in social functioning in ASD. Third, individuals with ASD show normative brain activity and selective social affiliative behaviors in response to people that they know but not to unfamiliar people. We propose a conceptual framework to reformulate and address these three theoretical impasses posed by ASD, arguing that the dissociable pathways of child-parent bonding and social development in ASD are shaped by (1) a dissociation between externally-driven and internally-driven attachment responses and (2) atypical learning dynamics occurring during child-caregiver bonding episodes, which are governed by and influence social-affiliation motives and other operant contingencies. Copyright © 2016 Elsevier B.V. All rights reserved.

Controlling Cell Function with Geometry

NASA Astrophysics Data System (ADS)

Mrksich, Milan

2012-02-01

This presentation will describe the use of patterned substrates to control cell shape with examples that illustrate the ways in which cell shape can regulate cell function. Most cells are adherent and must attach to and spread on a surface in order to survive, proliferate and function. In tissue, this surface is the extracellular matrix (ECM), an insoluble scaffold formed by the assembly of several large proteins---including fibronectin, the laminins and collagens and others---but in the laboratory, the surface is prepared by adsorbing protein to glass slides. To pattern cells, gold-coated slides are patterned with microcontact printing to create geometric features that promote cell attachment and that are surrounded by inert regions. Cells attach to these substrates and spread to adopt the shape defined by the underlying pattern and remain stable in culture for several days. Examples will be described that used a series of shapes to reveal the relationship between the shape of the cell and the structure of its cytoskeleton. These geometric cues were used to control cell polarity and the tension, or contractility, present in the cytoskeleton. These rules were further used to control the shapes of mesenchymal stem cells and in turn to control the differentiation of these cells into specialized cell types. For example, stem cells that were patterned into a ``star'' shape preferentially differentiated into bone cells whereas those that were patterned into a ``flower'' shape preferred a fat cell fate. These influences of shape on differentiation depend on the mechanical properties of the cytoskeleton. These examples, and others, reveal that shape is an important cue that informs cell function and that can be combined with the more common soluble cues to direct and study cell function.

Modeling meiotic chromosome pairing: nuclear envelope attachment, telomere-led active random motion, and anomalous diffusion

PubMed Central

Marshall, Wallace F.; Fung, Jennifer C.

2016-01-01

The recognition and pairing of homologous chromosomes during meiosis is a complex physical and molecular process involving a combination of polymer dynamics and molecular recognition events. Two highly conserved features of meiotic chromosome behavior are the attachment of telomeres to the nuclear envelope and the active random motion of telomeres driven by their interaction with cytoskeletal motor proteins. Both of these features have been proposed to facilitate the process of homolog pairing, but exactly what role these features play in meiosis remains poorly understood. Here we investigate the roles of active motion and nuclear envelope tethering using a Brownian dynamics simulation in which meiotic chromosomes are represented by a Rouse polymer model subjected to tethering and active forces at the telomeres. We find that tethering telomeres to the nuclear envelope slows down pairing relative to the rates achieved by un-attached chromosomes, but that randomly-directed active forces applied to the telomeres speeds up pairing dramatically in a manner that depends on the statistical properties of the telomere force fluctuations. The increased rate of initial pairing cannot be explained by stretching out of the chromosome conformation but instead seems to correlate with anomalous diffusion of sub-telomeric regions. PMID:27046097

The Fluid Dynamics of Nascent Biofilms

NASA Astrophysics Data System (ADS)

Farthing, Nicola; Snow, Ben; Wilson, Laurence; Bees, Martin

2017-11-01

Many anti-biofilm approaches target mature biofilms with biochemical or physio-chemical interventions. We investigate the mechanics of interventions at an early stage that aim to inhibit biofilm maturation, focusing on hydrodynamics as cells transition from planktonic to surface-attached. Surface-attached cells generate flow fields that are relatively long-range compared with cells that are freely-swimming. We look at the effect of these flows on the biofilm formation. In particular, we use digital inline holographic microscopy to determine the three-dimensional flow due to a surface-attached cell and the effect this flow has on both tracers and other cells in the fluid. We compare experimental data with two models of cells on boundaries. The first approach utilizes slender body theory and captures many of the features of the experimental field. The second model develops a simple description in terms of singularity solutions of Stokes' flow, which produces qualitatively similar dynamics to both the experiments and more complex model but with significant computational savings. The range of validity of multiple cell arrangements is investigated. These two descriptions can be used to investigate the efficacy of actives developed by Unilever on nascent biofilms.

Differential nuclear shape dynamics of invasive andnon-invasive breast cancer cells are associated with actin cytoskeleton organization and stability.

PubMed

Chiotaki, Rena; Polioudaki, Hara; Theodoropoulos, Panayiotis A

2014-08-01

Cancer cells often exhibit characteristic aberrations in their nuclear architecture, which are indicative of their malignant potential. In this study, we have examined the nuclear and cytoskeletal composition, attachment configuration dynamics, and osmotic or drug treatment response of invasive (Hs578T and MDA-MB-231) and non-invasive (MCF-10A and MCF-7) breast cancer cell lines. Unlike MCF-10A and MCF-7, Hs578T and MDA-MB-231 cells showed extensive nuclear elasticity and deformability and displayed distinct kinetic profiles during substrate attachment. The nuclear shape of MCF-10A and MCF-7 cells remained almost unaffected upon detachment, hyperosmotic shock, or cytoskeleton depolymerization, while Hs578T and MDA-MB-231 revealed dramatic nuclear contour malformations following actin reorganization.

Internal Dynamics of Water Attached to a Photoacidic Substrate: High Resolution Electronic Spectroscopy of β-NAPHTHOL-WATER in the Gas Phase.

NASA Astrophysics Data System (ADS)

Fleisher, Adam J.; Young, Justin W.; Pratt, David W.

2010-06-01

An understanding of the structure and internal dynamics of water attached to the photoacid β-naphthol is attainable through rotationally resolved electronic spectroscopy. Here, we present rotational constants for the 1:1 acid-base cluster in both S0 and S1, which provide the location of water within the cluster, as well as the barrier height to internal rotation of water in each electronic state. The barrier height decreases slightly upon excitation, from 206 wn in S0, to 182 wn in S1. There is also little evidence of a large change in water location, orientation, or overall hydrogen bond length upon irradiation with UV light. Thus, a single water molecule has relatively little affect on the substrate photo-acidity measured in the liquid phase.

Validation of Laser-Induced Fluorescent Photogrammetric Targets on Membrane Structures

NASA Technical Reports Server (NTRS)

Jones, Thomas W.; Dorrington, Adrian A.; Shortis, Mark R.; Hendricks, Aron R.

2004-01-01

The need for static and dynamic characterization of a new generation of inflatable space structures requires the advancement of classical metrology techniques. A new photogrammetric-based method for non-contact ranging and surface profiling has been developed at NASA Langley Research Center (LaRC) to support modal analyses and structural validation of this class of space structures. This full field measurement method, known as Laser-Induced Fluorescence (LIF) photogrammetry, has previously yielded promising experimental results. However, data indicating the achievable measurement precision had not been published. This paper provides experimental results that indicate the LIF-photogrammetry measurement precision for three different target types used on a reflective membrane structure. The target types were: (1) non-contact targets generated using LIF, (2) surface attached retro-reflective targets, and (3) surface attached diffuse targets. Results from both static and dynamic investigations are included.

Joint Use of ERT, Tracer, and Numerical Techniques to Image Preferential Flow Paths in a Fractured Granite Aquifer

NASA Astrophysics Data System (ADS)

Sanaga, S.; Vijay, S.; Kbvn, P.; Peddinti, S. R.; P S L, S.

2017-12-01

Fractured geologic media poses formidable challenges to hydrogeologists due of the strenuous mapping of fracture-matrix system and quantification of flow and transport processes. In this research, we demonstrated the efficacy of tracer-ERT studies coupled with numerical simulations to delineate preferential flow paths in a fractured granite aquifer of Deccan traps in India. A series of natural gradient saline tracer experiments were conducted from a depth window of 18 to 22 m in an injection well located inside the IIT Hyderabad campus. Tracer migration was monitored in a time-lapse mode using two cross-sectional surface ERT profiles placed in the direction of flow gradient. Dynamic changes in sub-surface electrical properties inferred via resistivity anomalies were used to highlight preferential flow paths of the study area. ERT-derived tracer breakthrough curves were in agreement with geochemical sample measurements (R2=0.74). Fracture geometry and hydraulic properties derived from ERT and pumping tests were then used to evaluate two mathematical conceptualizations that are relevant to fractured aquifers. Results of numerical analysis conclude that a dual continuum model that combines matrix and fracture systems through a flow exchange term has outperformed equivalent continuum model in reproducing tracer concentrations at the monitoring wells (evident by decrease in RMSE from 199 mg/l to 65 mg/l). A sensitivity analysis of the model parameters reveals that spatial variability in hydraulic conductivity, local-scale dispersion, and flow exchange at fracture-matrix interface have a profound effect on model simulations. Keywords: saline tracer, ERT, fractured granite, groundwater, preferential flow, numerical simulation

Experience-Dependent Hemispheric Specialization of Letters and Numbers is Revealed in Early Visual Processing

PubMed Central

Park, Joonkoo; Chiang, Crystal; Brannon, Elizabeth M.; Woldorff, Marty G.

2014-01-01

Recent functional magnetic resonance imaging research has demonstrated that letters and numbers are preferentially processed in distinct regions and hemispheres in the visual cortex. In particular, the left visual cortex preferentially processes letters compared to numbers, while the right visual cortex preferentially processes numbers compared to letters. Because letters and numbers are cultural inventions and are otherwise physically arbitrary, such a double dissociation is strong evidence for experiential effects on neural architecture. Here, we use the high temporal resolution of event-related potentials (ERPs) to investigate the temporal dynamics of the neural dissociation between letters and numbers. We show that the divergence between ERP traces to letters and numbers emerges very early in processing. Letters evoked greater N1 waves (latencies 140–170 ms) than did numbers over left occipital channels, while numbers evoked greater N1s than letters over the right, suggesting letters and numbers are preferentially processed in opposite hemispheres early in visual encoding. Moreover, strings of letters, but not single letters, elicited greater P2 ERP waves, (starting around 250 ms) than numbers did over the left hemisphere, suggesting that the visual cortex is tuned to selectively process combinations of letters, but not numbers, further along in the visual processing stream. Additionally, the processing of both of these culturally defined stimulus types differentiated from similar but unfamiliar visual stimulus forms (false fonts) even earlier in the processing stream (the P1 at 100 ms). These findings imply major cortical specialization processes within the visual system driven by experience with reading and mathematics. PMID:24669789

Experience-dependent hemispheric specialization of letters and numbers is revealed in early visual processing.

PubMed

Park, Joonkoo; Chiang, Crystal; Brannon, Elizabeth M; Woldorff, Marty G

2014-10-01

Recent fMRI research has demonstrated that letters and numbers are preferentially processed in distinct regions and hemispheres in the visual cortex. In particular, the left visual cortex preferentially processes letters compared with numbers, whereas the right visual cortex preferentially processes numbers compared with letters. Because letters and numbers are cultural inventions and are otherwise physically arbitrary, such a double dissociation is strong evidence for experiential effects on neural architecture. Here, we use the high temporal resolution of ERPs to investigate the temporal dynamics of the neural dissociation between letters and numbers. We show that the divergence between ERP traces to letters and numbers emerges very early in processing. Letters evoked greater N1 waves (latencies 140-170 msec) than did numbers over left occipital channels, whereas numbers evoked greater N1s than letters over the right, suggesting letters and numbers are preferentially processed in opposite hemispheres early in visual encoding. Moreover, strings of letters, but not single letters, elicited greater P2 ERP waves (starting around 250 msec) than numbers did over the left hemisphere, suggesting that the visual cortex is tuned to selectively process combinations of letters, but not numbers, further along in the visual processing stream. Additionally, the processing of both of these culturally defined stimulus types differentiated from similar but unfamiliar visual stimulus forms (false fonts) even earlier in the processing stream (the P1 at 100 msec). These findings imply major cortical specialization processes within the visual system driven by experience with reading and mathematics.

The effect of a silicone wristband in dynamic balance.

PubMed

Teruya, Thiago Toshi; Matareli, Bruno Machado; Soares Romano, Fillipe; Mochizuki, Luis

2013-10-01

The effect of a wristband on the dynamic balance of young adults was assessed. Twenty healthy young adults wore a commercial Power BalanceT or fake silicone wristband. A 3D accelerometer was attached to their lumbar region to measure body sway. They played the video game Tightrope (Wii video game console) with and without a wristband; body sway acceleration was measured. Mean balance sway acceleration and its variability were the same in all conditions, so silicone wristbands do not modify dynamic balance control.

Personalized recommendation based on preferential bidirectional mass diffusion

NASA Astrophysics Data System (ADS)

Chen, Guilin; Gao, Tianrun; Zhu, Xuzhen; Tian, Hui; Yang, Zhao

2017-03-01

Recommendation system provides a promising way to alleviate the dilemma of information overload. In physical dynamics, mass diffusion has been used to design effective recommendation algorithms on bipartite network. However, most of the previous studies focus overwhelmingly on unidirectional mass diffusion from collected objects to uncollected objects, while overlooking the opposite direction, leading to the risk of similarity estimation deviation and performance degradation. In addition, they are biased towards recommending popular objects which will not necessarily promote the accuracy but make the recommendation lack diversity and novelty that indeed contribute to the vitality of the system. To overcome the aforementioned disadvantages, we propose a preferential bidirectional mass diffusion (PBMD) algorithm by penalizing the weight of popular objects in bidirectional diffusion. Experiments are evaluated on three benchmark datasets (Movielens, Netflix and Amazon) by 10-fold cross validation, and results indicate that PBMD remarkably outperforms the mainstream methods in accuracy, diversity and novelty.

Computational study of the interplay between intermolecular interactions and CO2 orientations in type I hydrates.

PubMed

Pérez-Rodríguez, M; Vidal-Vidal, A; Míguez, J M; Blas, F J; Torré, J-P; Piñeiro, M M

2017-01-25

Carbon dioxide (CO 2 ) molecules show a rich orientation landscape when they are enclathrated in type I hydrates. Previous studies have described experimentally their preferential orientations, and some theoretical works have explained, but only partially, these experimental results. In the present paper, we use classical molecular dynamics and electronic density functional theory to advance in the theoretical description of CO 2 orientations within type I hydrates. Our results are fully compatible with those previously reported, both theoretical and experimental, the geometric shape of the cavities in hydrate being, and therefore, the steric constraints, responsible for some (but not all) preferential angles. In addition, our calculations also show that guest-guest interactions in neighbouring cages are a key factor to explain the remaining experimental angles. Besides the implication concerning equation of state hydrate modeling approximations, the conclusion is that these guest-guest interactions should not be neglected, contrary to the usual practice.

Mechanism of lignin inhibition of enzymatic biomass deconstruction

DOE PAGES

Vermaas, Josh V.; Petridis, Loukas; Qi, Xianghong; ...

2015-12-01

The conversion of plant biomass to ethanol via enzymatic cellulose hydrolysis offers a potentially sustainable route to biofuel production. However, the inhibition of enzymatic activity in pretreated biomass by lignin severely limits the efficiency of this process. By performing atomic-detail molecular dynamics simulation of a biomass model containing cellulose, lignin, and cellulases (TrCel7A), we elucidate detailed lignin inhibition mechanisms. We find that lignin binds preferentially both to the elements of cellulose to which the cellulases also preferentially bind (the hydrophobic faces) and also to the specific residues on the cellulose-binding module of the cellulase that are critical for cellulose bindingmore » of TrCel7A (Y466, Y492, and Y493). In conclusion, lignin thus binds exactly where for industrial purposes it is least desired, providing a simple explanation of why hydrolysis yields increase with lignin removal.« less

Trajectories of Mothers' Emotional Availability: Relations with Infant Temperament in Predicting Attachment Security

PubMed Central

Kim, Bo-Ram; Chow, Sy-Miin; Bray, Bethany; Teti, Douglas M.

2017-01-01

The present study examined observations of parenting quality (mothers' emotional availability - EA) during infant bedtimes at 4 points across the infants' first year, assessing relations between levels and trajectories of emotional availability and infant attachment at 12 months and the role of infant temperament in moderating these associations. The sample (N = 128) was predominantly Euro-American (82.5%) and at low socioeconomic risk. Latent growth curve modeling with latent basis coefficients indicated substantial individual differences in initial levels and slopes in EA trajectories across the first year. Both levels of maternal EA and EA trajectories across the first year predicted 12-month infant attachment security. Although maternal EA tended to decrease across the first year in the full sample, EA trajectories that showed a “bounce-back” between 6 and 12 months, suggesting more successful maternal adaptation to an expanding infant developmental repertoire, predicted greater infant security at 12 months. In addition, linkages between latent EA trajectories and 12-month attachment were moderated by 3-month infant temperamental reactivity and regulation. These findings indicate that infant attachment security is sensitive to both static and dynamic aspects of parenting quality across the first year, and that infant temperament can interact with both in predicting infant attachment. PMID:27852132

Trajectories of mothers' emotional availability: relations with infant temperament in predicting attachment security.

PubMed

Kim, Bo-Ram; Chow, Sy-Miin; Bray, Bethany; Teti, Douglas M

2017-02-01

The present study examined observations of parenting quality (mothers' emotional availability - EA) during infant bedtimes at 4 points across the infants' first year, assessing relations between levels and trajectories of EA and infant attachment at 12 months and the role of infant temperament in moderating these associations. The sample (N = 128) was predominantly Euro-American (82.5%) and at low socioeconomic risk. Latent growth curve modeling with latent basis coefficients indicated substantial individual differences in initial levels and slopes in EA trajectories across the first year. Both levels of maternal EA and EA trajectories across the first year predicted 12-month infant attachment security. Although maternal EA tended to decrease across the first year in the full sample, EA trajectories that showed a "bounce-back" between 6 and 12 months, suggesting more successful maternal adaptation to an expanding infant developmental repertoire, predicted greater infant security at 12 months. In addition, linkages between latent EA trajectories and 12-month attachment were moderated by 3-month infant temperamental reactivity and regulation. These findings indicate that infant attachment security is sensitive to both static and dynamic aspects of parenting quality across the first year, and that infant temperament can interact with both in predicting infant attachment.

Method and apparatus for real time imaging and monitoring of radiotherapy beams

DOEpatents

Majewski, Stanislaw [Yorktown, VA; Proffitt, James [Newport News, VA; Macey, Daniel J [Birmingham, AL; Weisenberger, Andrew G [Yorktown, VA

2011-11-01

A method and apparatus for real time imaging and monitoring of radiation therapy beams is designed to preferentially distinguish and image low energy radiation from high energy secondary radiation emitted from a target as the result of therapeutic beam deposition. A detector having low sensitivity to high energy photons combined with a collimator designed to dynamically image in the region of the therapeutic beam target is used.

Similarities and differences of serotonin and its precursors in their interactions with model membranes studied by molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Wood, Irene; Martini, M. Florencia; Pickholz, Mónica

2013-08-01

In this work, we report a molecular dynamics (MD) simulations study of relevant biological molecules as serotonin (neutral and protonated) and its precursors, tryptophan and 5-hydroxy-tryptophan, in a fully hydrated bilayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidyl-choline (POPC). The simulations were carried out at the fluid lamellar phase of POPC at constant pressure and temperature conditions. Two guest molecules of each type were initially placed at the water phase. We have analyzed, the main localization, preferential orientation and specific interactions of the guest molecules within the bilayer. During the simulation run, the four molecules were preferentially found at the water-lipid interphase. We found that the interactions that stabilized the systems are essentially hydrogen bonds, salt bridges and cation-π. None of the guest molecules have access to the hydrophobic region of the bilayer. Besides, zwitterionic molecules have access to the water phase, while protonated serotonin is anchored in the interphase. Even taking into account that these simulations were done using a model membrane, our results suggest that the studied molecules could not cross the blood brain barrier by diffusion. These results are in good agreement with works that show that serotonin and Trp do not cross the BBB by simple diffusion.

Determinants of FDI Localization in China: A County-Level Analysis for the Pharmaceutical Industry

PubMed Central

Li, Su; Angelino, Antonio; Yin, Haitao

2017-01-01

Foreign direct investments (FDIs) have been widely recognized as a crucial feature of the Chinese industrial development process. Over the past decades, China has been attracting huge amounts of inward FDIs as a consequence of both spontaneous market dynamics and place-based preferential policies at the sub-national level. However, the Chinese market exhibits large dissimilarities in terms of FDI localization across territories that are worth investigating at a more disaggregated level. In this regards, our study explores the determinants of attraction of inward FDIs in China, at the county level. It focuses on the pharmaceutical industry and attempts to assess whether factors related to location advantages, agglomeration dynamics, information cost effects and environmental regulation costs affect foreign firms’ localization choices as well as invested amounts in that location. By means of discrete choice models, our paper confirms the findings of the prevalent literature about the positive effects of location advantages on pharmaceutical FDI attraction. Different from our expectations, a higher proportion of foreign enterprises do not stimulate significant effects on FDI localization, while preferential policies and sectoral agglomeration are positively correlated with the localization of pharmaceutical foreign firms. Finally, our results suggest that investing firms tend to avoid areas with strict environment regulation. PMID:28867815

Determinants of FDI Localization in China: A County-Level Analysis for the Pharmaceutical Industry.

PubMed

Li, Su; Angelino, Antonio; Yin, Haitao; Spigarelli, Francesca

2017-08-30

Foreign direct investments (FDIs) have been widely recognized as a crucial feature of the Chinese industrial development process. Over the past decades, China has been attracting huge amounts of inward FDIs as a consequence of both spontaneous market dynamics and place-based preferential policies at the sub-national level. However, the Chinese market exhibits large dissimilarities in terms of FDI localization across territories that are worth investigating at a more disaggregated level. In this regards, our study explores the determinants of attraction of inward FDIs in China, at the county level. It focuses on the pharmaceutical industry and attempts to assess whether factors related to location advantages, agglomeration dynamics, information cost effects and environmental regulation costs affect foreign firms' localization choices as well as invested amounts in that location. By means of discrete choice models, our paper confirms the findings of the prevalent literature about the positive effects of location advantages on pharmaceutical FDI attraction. Different from our expectations, a higher proportion of foreign enterprises do not stimulate significant effects on FDI localization, while preferential policies and sectoral agglomeration are positively correlated with the localization of pharmaceutical foreign firms. Finally, our results suggest that investing firms tend to avoid areas with strict environment regulation.

Experimental investigation of compliant wall surface deformation in a turbulent channel flow

NASA Astrophysics Data System (ADS)

Zhang, Cao; Wang, Jin; Katz, Joseph

2016-11-01

The dynamic response of a compliant wall under a turbulent channel flow is investigated by simultaneously measuring the time-resolved, 3D flow field (using tomographic PIV) and the 2D surface deformation (using interferometry). The pressure distributions are calculated by spatially integrating the material acceleration field. The Reynolds number is Reτ = 2300, and the centerline velocity (U0) is 15% of the material shear speed. The wavenumber-frequency spectra of the wall deformation contain a non-advected low-frequency component and advected modes, some traveling downstream at U0 and others at 0.72U0. Trends in the wall dynamics are elucidated by correlating the deformation with flow variables. The spatial pressure-deformation correlations peak at y/ h 0.12 (h is half channel height), the elevation of Reynolds shear stress maximum in the log-layer. Streamwise lagging of the deformation behind the pressure is caused in part by phase-lag of the pressure with decreasing distance from the wall, and in part by material damping. Positive deformations (bumps) are preferentially associated with ejections, which involve spanwise vortices located downstream and quasi-streamwise vortices with spanwise offset, consistent with hairpin-like structures. The negative deformations (dents) are preferentially associated with pressure maxima at the transition between an upstream sweep to a downstream ejection. Sponsored by ONR.

ARC-2006-ACD06-0177-014

NASA Image and Video Library

2006-10-10

CEV (Crew Escape Vehicle) capsule Balistic Range testing to examine static and dynamic stability characteristics (at the Hypervelocity Free-Flight Facility) HFF - Don Bowling (l) attaching firing cable to breeth cap as Don Holt (r) looks on

Dismissing Attachment Characteristics Dynamically Modulate Brain Networks Subserving Social Aversion.

PubMed

Krause, Anna Linda; Borchardt, Viola; Li, Meng; van Tol, Marie-José; Demenescu, Liliana Ramona; Strauss, Bernhard; Kirchmann, Helmut; Buchheim, Anna; Metzger, Coraline D; Nolte, Tobias; Walter, Martin

2016-01-01

Attachment patterns influence actions, thoughts and feeling through a person's "inner working model". Speech charged with attachment-dependent content was proposed to modulate the activation of cognitive-emotional schemata in listeners. We performed a 7 Tesla rest-task-rest functional magnetic resonance imaging (fMRI)-experiment, presenting auditory narratives prototypical of dismissing attachment representations to investigate their effect on 23 healthy males. We then examined effects of participants' attachment style and childhood trauma on brain state changes using seed-based functional connectivity (FC) analyses, and finally tested whether subjective differences in responsivity to narratives could be predicted by baseline network states. In comparison to a baseline state, we observed increased FC in a previously described "social aversion network" including dorsal anterior cingulated cortex (dACC) and left anterior middle temporal gyrus (aMTG) specifically after exposure to insecure-dismissing attachment narratives. Increased dACC-seeded FC within the social aversion network was positively related to the participants' avoidant attachment style and presence of a history of childhood trauma. Anxious attachment style on the other hand was positively correlated with FC between the dACC and a region outside of the "social aversion network", namely the dorsolateral prefrontal cortex, which suggests decreased network segregation as a function of anxious attachment. Finally, the extent of subjective experience of friendliness towards the dismissing narrative was predicted by low baseline FC-values between hippocampus and inferior parietal lobule (IPL). Taken together, our study demonstrates an activation of networks related to social aversion in terms of increased connectivity after listening to insecure-dismissing attachment narratives. A causal interrelation of brain state changes and subsequent changes in social reactivity was further supported by our observation of direct prediction of neuronal responses by individual attachment and trauma characteristics and reversely prediction of subjective experience by intrinsic functional connections. We consider these findings of activation of within-network and between-network connectivity modulated by inter-individual differences as substantial for the understanding of interpersonal processes, particularly in clinical settings.

Quasi-equilibrium melting of quartzite upon extreme friction

NASA Astrophysics Data System (ADS)

Lee, Sung Keun; Han, Raehee; Kim, Eun Jeong; Jeong, Gi Young; Khim, Hoon; Hirose, Takehiro

2017-06-01

The friction on fault planes that controls how rocks slide during earthquakes decreases significantly as a result of complex fault-lubrication processes involving frictional melting. Fault friction has been characterized in terms of the preferential melting of minerals with low melting points--so-called disequilibrium melting. Quartz, which has a high melting temperature of about 1,726 °C and is a major component of crustal rocks, is not expected to melt often during seismic slip. Here we use high-velocity friction experiments on quartzite to show that quartz can melt at temperatures of 1,350 to 1,500 °C. This implies that quartz within a fault plane undergoing rapid friction sliding could melt at substantially lower temperatures than expected. We suggest that depression of the melting temperature is caused by the preferential melting of ultra-fine particles and metastable melting of β-quartz at about 1,400 °C during extreme frictional slip. The results for quartzite are applicable to complex rocks because of the observed prevalence of dynamic grain fragmentation, the preferential melting of smaller grains and the kinetic preference of β-quartz formation during frictional sliding. We postulate that frictional melting of quartz on a fault plane at temperatures substantially below the melting temperature could facilitate slip-weakening and lead to large earthquakes.

Preferential selection based on strategy persistence and memory promotes cooperation in evolutionary prisoner's dilemma games

NASA Astrophysics Data System (ADS)

Liu, Yuanming; Huang, Changwei; Dai, Qionglin

2018-06-01

Strategy imitation plays a crucial role in evolutionary dynamics when we investigate the spontaneous emergence of cooperation under the framework of evolutionary game theory. Generally, when an individual updates his strategy, he needs to choose a role model whom he will learn from. In previous studies, individuals choose role models randomly from their neighbors. In recent works, researchers have considered that individuals choose role models according to neighbors' attractiveness characterized by the present network topology or historical payoffs. Here, we associate an individual's attractiveness with the strategy persistence, which characterizes how frequently he changes his strategy. We introduce a preferential parameter α to describe the nonlinear correlation between the selection probability and the strategy persistence and the memory length of individuals M into the evolutionary games. We investigate the effects of α and M on cooperation. Our results show that cooperation could be promoted when α > 0 and at the same time M > 1, which corresponds to the situation that individuals are inclined to select their neighbors with relatively higher persistence levels during the evolution. Moreover, we find that the cooperation level could reach the maximum at an optimal memory length when α > 0. Our work sheds light on how to promote cooperation through preferential selection based on strategy persistence and a limited memory length.

Host discrimination in modular mutualisms: a theoretical framework for meta-populations of mutualists and exploiters

PubMed Central

Steidinger, Brian S.; Bever, James D.

2016-01-01

Plants in multiple symbioses are exploited by symbionts that consume their resources without providing services. Discriminating hosts are thought to stabilize mutualism by preferentially allocating resources into anatomical structures (modules) where services are generated, with examples of modules including the entire inflorescences of figs and the root nodules of legumes. Modules are often colonized by multiple symbiotic partners, such that exploiters that co-occur with mutualists within mixed modules can share rewards generated by their mutualist competitors. We developed a meta-population model to answer how the population dynamics of mutualists and exploiters change when they interact with hosts with different module occupancies (number of colonists per module) and functionally different patterns of allocation into mixed modules. We find that as module occupancy increases, hosts must increase the magnitude of preferentially allocated resources in order to sustain comparable populations of mutualists. Further, we find that mixed colonization can result in the coexistence of mutualist and exploiter partners, but only when preferential allocation follows a saturating function of the number of mutualists in a module. Finally, using published data from the fig–wasp mutualism as an illustrative example, we derive model predictions that approximate the proportion of exploiter, non-pollinating wasps observed in the field. PMID:26740613

The influence of gravity on the distribution of the deposit formed onto a substrate by sessile, hanging, and sandwiched hanging drop evaporation.

PubMed

Sandu, Ion; Fleaca, Claudiu Teodor

2011-06-15

The focus of the present article is the study of the influence of gravity on the particle deposition profiles on a solid substrate during the evaporation of sessile, hanging and sandwiched hanging drops of colloidal particle suspensions. For concentrations of nanoparticles in the colloidal solutions in the range 0.0001-1 wt.%, highly diluted suspensions will preferentially form rings while concentrated suspensions will preferentially form spots in both sessile and hanging drop evaporation. For intermediary concentrations, the particle deposition profiles will depend on the nanoparticle aggregation dynamics in the suspension during the evaporation process, gravity and on the detailed evaporation geometry. The evaporation of a drop of toluene/carbon nanoparticle suspension hanging from a pendant water drop will leave on the substrate a circular spot with no visible external ring. By contrast, a clear external ring is formed on the substrate by the sessile evaporation of a similar drop of suspension sandwiched between a water drop and the substrate. From the application viewpoint, these processes can be used to create preferential electrical conductive carbon networks and contacts for arrays of self-assembled nanostructures fabricated on solid substrates as well as on flexible polymeric substrates. Copyright © 2011 Elsevier Inc. All rights reserved.

c-axis preferential orientation of hydroxyapatite accounts for the high wear resistance of the teeth of black carp (Mylopharyngodon piceus)

PubMed Central

Fu, Jimin; He, Chong; Xia, Biao; Li, Yan; Feng, Qiong; Yin, Qifang; Shi, Xinghua; Feng, Xue; Wang, Hongtao; Yao, Haimin

2016-01-01

Biological armors such as mollusk shells have long been recognized and studied for their values in inspiring novel designs of engineering materials with higher toughness and strength. However, no material is invincible and biological armors also have their rivals. In this paper, our attention is focused on the teeth of black carp (Mylopharyngodon piceus) which is a predator of shelled mollusks like snails and mussels. Nanoscratching test on the enameloid, the outermost layer of the teeth, indicates that the natural occlusal surface (OS) has much higher wear resistance compared to the other sections. Subsequent X-ray diffraction analysis reveals that the hydroxyapatite (HAp) crystallites in the vicinity of OS possess c-axis preferential orientation. The superior wear resistance of black carp teeth is attributed to the c-axis preferential orientation of HAp near the OS since the (001) surface of HAp crystal, which is perpendicular to the c-axis, exhibits much better wear resistance compared to the other surfaces as demonstrated by the molecular dynamics simulation. Our results not only shed light on the origin of the good wear resistance exhibited by the black carp teeth but are of great value to the design of engineering materials with better abrasion resistance. PMID:27001150

Why social attachment and oxytocin protect against addiction and stress: Insights from the dynamics between ventral and dorsal corticostriatal systems.

PubMed

Tops, Mattie; Koole, Sander L; IJzerman, Hans; Buisman-Pijlman, Femke T A

2014-04-01

The present article advances a neurobiological model of the reciprocal associations between social attachment and drug abuse, and social attachment and chronic stress, as overlapping systems are involved in stress coping and social attachment. In terms of coping, responding to a novel stressor or challenge involves initial novelty processing and activation of learning mechanisms that allow habituation to the stressor through familiarization. Similarly, social attachments are initially formed by being attracted by rewarding properties of an as-yet novel individual, and subsequently developing feelings of attachment towards the familiarized individual. Attachment and familiarization increase the availability of "internal working models" for the control of behavior and emotion, which may explain why secure attachments are associated with increased resilience in the face of stress, accompanied by less reactive reward responding (i.e., increased resilience against drug addiction). The present article seeks to illuminate the role of the neuropeptide oxytocin, which may be involved in the overlapping mechanisms of stable attachment formation and stress coping by shifting processing from novelty and reward seeking to appreciation of familiarity. Oxytocin may accomplish this by facilitating a ventral-to-dorsal shift in activation in corticostriatal loops, which produces a shift from a reactive reward drive (wanting) to stable appreciation of familiar social aspects ("liking" or "loving"). The authors suggest that through dopaminergic, serotonergic and endogenous opioid mechanisms, oxytocin is involved in shifting the balance between wanting and liking in corticostriatal loops by facilitating consolidation of social information from ventral reactive reward systems to dorsal internal working models that aid in prospectively selecting optimal actions in the future, increasing resilience in the face of stress and addiction. © 2013.

Perceptions about parents' relationship and parenting quality, attachment styles, and young adults' intimate expectations: a cluster analytic approach.

PubMed

Einav, Michal

2014-01-01

This study examines the associations between young adults' perceptions of their parents' intimate relationship and the quality of their parenting as predictors of their children's expectations about intimacy in their own future relationships. A sample of 111 young adults completed questionnaires assessing their perceptions regarding their parents' intimate relationship and parenting quality, their own attachment styles, and their own expectations regarding intimate relationships. A correlational analysis revealed a positive link between the parents' relationship and parenting quality, and between parenting quality and expectations about intimacy, which supports the attachment theory. A cluster analysis identified three distinct groups of parental profiles interrelated with attachment styles that had varying effects on their children's expectations about intimacy. These findings emphasize the unique characteristics of parental relations in the family of origin relations, which have an enduring effect on the interpersonal styles of adult children, providing additional support to an integrated, intergenerational approach to family dynamics.

Distribution and Dynamic Properties of Xenon Dissolved in the Ionic Smectic Phase of [C16mim][NO3]: MD Simulation and Theoretical Model.

PubMed

Frezzato, Diego; Saielli, Giacomo

2016-03-10

We have investigated the structural and dynamic properties of Xe dissolved in the ionic liquid crystal (ILC) phase of 1-hexadecyl-3-methylimidazolium nitrate using classical molecular dynamics (MD) simulations. Xe is found to be preferentially dissolved within the hydrophobic environment of the alkyl chains rather than in the ionic layers of the smectic phase. The structural parameters and the estimated local diffusion coefficients concerning the short-time motion of Xe are used to parametrize a theoretical model based on the Smoluchowski equation for the macroscopic dynamics across the smectic layers, a feature which cannot be directly obtained from the relatively short MD simulations. This protocol represents an efficient combination of computational and theoretical tools to obtain information on slow processes concerning the permeability and diffusivity of the xenon in smectic ILCs.

Molecular dynamics studies of interfacial water at the alumina surface.

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

Argyris, Dr. Dimitrios; Ho, Thomas; Cole, David

2011-01-01

Interfacial water properties at the alumina surface were investigated via all-atom equilibrium molecular dynamics simulations at ambient temperature. Al-terminated and OH-terminated alumina surfaces were considered to assess the structural and dynamic behavior of the first few hydration layers in contact with the substrates. Density profiles suggest water layering up to {approx}10 {angstrom} from the solid substrate. Planar density distribution data indicate that water molecules in the first interfacial layer are organized in well-defined patterns dictated by the atomic terminations of the alumina surface. Interfacial water exhibits preferential orientation and delayed dynamics compared to bulk water. Water exhibits bulk-like behavior atmore » distances greater than {approx}10 {angstrom} from the substrate. The formation of an extended hydrogen bond network within the first few hydration layers illustrates the significance of water?water interactions on the structural properties at the interface.« less

Optimal forwarding ratio on dynamical networks with heterogeneous mobility

NASA Astrophysics Data System (ADS)

Gan, Yu; Tang, Ming; Yang, Hanxin

2013-05-01

Since the discovery of non-Poisson statistics of human mobility trajectories, more attention has been paid to understand the role of these patterns in different dynamics. In this study, we first introduce the heterogeneous mobility of mobile agents into dynamical networks, and then investigate packet forwarding strategy on the heterogeneous dynamical networks. We find that the faster speed and the higher proportion of high-speed agents can enhance the network throughput and reduce the mean traveling time in random forwarding. A hierarchical structure in the dependence of high-speed is observed: the network throughput remains unchanged at small and large high-speed value. It is also interesting to find that a slightly preferential forwarding to high-speed agents can maximize the network capacity. Through theoretical analysis and numerical simulations, we show that the optimal forwarding ratio stems from the local structural heterogeneity of low-speed agents.

Stereodynamics in state-resolved scattering at the gas–liquid interface

PubMed Central

Perkins, Bradford G.; Nesbitt, David J.

2008-01-01

Stereodynamics at the gas–liquid interface provides insight into the important physical interactions that directly influence heterogeneous chemistry at the surface and within the bulk liquid. We investigate molecular beam scattering of CO2 from a liquid perfluoropolyether (PFPE) surface in vacuum [incident energy Einc = 10.6(8) kcal/mol, incident angle θinc = 60°] to specifically reveal rotational angular-momentum directions for scattered molecules. Experimentally, internal quantum state populations and MJ distributions are probed by high-resolution polarization-modulated infrared laser spectroscopy. Analysis of J-state populations reveals dual-channel scattering dynamics characterized by a two-temperature Boltzmann distribution for trapping–desorption and impulsive scattering. In addition, molecular dynamics simulations of CO2 + fluorinated self-assembled monolayers have been used to model CO2 + PFPE dynamics. Experimental results and molecular dynamics simulations reveal highly oriented CO2 distributions that preferentially scatter with “top spin” as a strongly increasing function of J state. PMID:18678907

High-frequency vibration energy harvesting from impulsive excitation utilizing intentional dynamic instability caused by strong nonlinearity

NASA Astrophysics Data System (ADS)

Remick, Kevin; Dane Quinn, D.; Michael McFarland, D.; Bergman, Lawrence; Vakakis, Alexander

2016-05-01

The authors investigate a vibration-based energy harvesting system utilizing essential (nonlinearizable) nonlinearities and electromagnetic coupling elements. The system consists of a grounded, weakly damped linear oscillator (primary system) subjected to a single impulsive load. This primary system is coupled to a lightweight, damped oscillating attachment (denoted as nonlinear energy sink, NES) via a neodymium magnet and an inductance coil, and a piano wire, which generates an essential geometric cubic stiffness nonlinearity. Under impulsive input, the transient damped dynamics of this system exhibit transient resonance captures (TRCs) causing intentional large-amplitude and high-frequency instabilities in the response of the NES. These TRCs result in strong energy transfer from the directly excited primary system to the light-weight attachment. The energy is harvested by the electromagnetic elements in the coupling and, in the present case, dissipated in a resistive element in the electrical circuit. The primary goal of this work is to numerically, analytically, and experimentally demonstrate the efficacy of employing this type of intentional high-frequency dynamic instability to achieve enhanced vibration energy harvesting under impulsive excitation.

Directing Stem Cell Differentiation via Electrochemical Reversible Switching between Nanotubes and Nanotips of Polypyrrole Array.

PubMed

Wei, Yan; Mo, Xiaoju; Zhang, Pengchao; Li, Yingying; Liao, Jingwen; Li, Yongjun; Zhang, Jinxing; Ning, Chengyun; Wang, Shutao; Deng, Xuliang; Jiang, Lei

2017-06-27

Control of stem cell behaviors at solid biointerfaces is critical for stem-cell-based regeneration and generally achieved by engineering chemical composition, topography, and stiffness. However, the influence of dynamic stimuli at the nanoscale from solid biointerfaces on stem cell fate remains unclear. Herein, we show that electrochemical switching of a polypyrrole (Ppy) array between nanotubes and nanotips can alter surface adhesion, which can strongly influence mechanotransduction activation and guide differentiation of mesenchymal stem cells (MSCs). The Ppy array, prepared via template-free electrochemical polymerization, can be reversibly switched between highly adhesive hydrophobic nanotubes and poorly adhesive hydrophilic nanotips through an electrochemical oxidation/reduction process, resulting in dynamic attachment and detachment to MSCs at the nanoscale. Multicyclic attachment/detachment of the Ppy array to MSCs can activate intracellular mechanotransduction and osteogenic differentiation independent of surface stiffness and chemical induction. This smart surface, permitting transduction of nanoscaled dynamic physical inputs into biological outputs, provides an alternative to classical cell culture substrates for regulating stem cell fate commitment. This study represents a general strategy to explore nanoscaled interactions between stem cells and stimuli-responsive surfaces.

GSK3- and PRMT-1–dependent modifications of desmoplakin control desmoplakin–cytoskeleton dynamics

PubMed Central

Albrecht, Lauren V.; Zhang, Lichao; Shabanowitz, Jeffrey; Purevjav, Enkhsaikhan; Towbin, Jeffrey A.; Hunt, Donald F.

2015-01-01

Intermediate filament (IF) attachment to intercellular junctions is required for skin and heart integrity, but how the strength and dynamics of this attachment are modulated during normal and pathological remodeling is poorly understood. We show that glycogen synthase kinase 3 (GSK3) and protein arginine methyltransferase 1 (PRMT-1) cooperate to orchestrate a series of posttranslational modifications on the IF-anchoring protein desmoplakin (DP) that play an essential role in coordinating cytoskeletal dynamics and cellular adhesion. Front-end electron transfer dissociation mass spectrometry analyses of DP revealed six novel serine phosphorylation sites dependent on GSK3 signaling and four novel arginine methylation sites including R2834, the mutation of which has been associated with arrhythmogenic cardiomyopathy (AC). Inhibition of GSK3 or PRMT-1 or overexpression of the AC-associated mutant R2834H enhanced DP–IF associations and delayed junction assembly. R2834H blocked the GSK3 phosphorylation cascade and reduced DP–GSK3 interactions in cultured keratinocytes and in the hearts of transgenic R2834H DP mice. Interference with this regulatory machinery may contribute to skin and heart diseases. PMID:25733715

Mechanisms of oriented attachment of TiO2 nanocrystals in vacuum and humid environments: reactive molecular dynamics.

PubMed

Raju, Muralikrishna; van Duin, Adri C T; Fichthorn, Kristen A

2014-01-01

Oriented attachment (OA) of nanocrystals is now widely recognized as a key process in the solution-phase growth of hierarchical nanostructures. However, the microscopic origins of OA remain unclear. We perform molecular dynamics simulations using a recently developed ReaxFF reactive force field to study the aggregation of various titanium dioxide (anatase) nanocrystals in vacuum and humid environments. In vacuum, the nanocrystals merge along their direction of approach, resulting in a polycrystalline material. By contrast, in the presence of water vapor the nanocrystals reorient themselves and aggregate via the OA mechanism to form a single or twinned crystal. They accomplish this by creating a dynamic network of hydrogen bonds between surface hydroxyls and surface oxygens of aggregating nanocrystals. We determine that OA is dominant on surfaces that have the greatest propensity to dissociate water. Our results are consistent with experiment, are likely to be general for aqueous oxide systems, and demonstrate the critical role of solvent in nanocrystal aggregation. This work opens up new possibilities for directing nanocrystal growth to fabricate nanomaterials with desired shapes and sizes.

Permeability and kinetic coefficients for mesoscale BCF surface step dynamics: Discrete two-dimensional deposition-diffusion equation analysis

DOE PAGES

Zhao, Renjie; Evans, James W.; Oliveira, Tiago J.

2016-04-08

Here, a discrete version of deposition-diffusion equations appropriate for description of step flow on a vicinal surface is analyzed for a two-dimensional grid of adsorption sites representing the stepped surface and explicitly incorporating kinks along the step edges. Model energetics and kinetics appropriately account for binding of adatoms at steps and kinks, distinct terrace and edge diffusion rates, and possible additional barriers for attachment to steps. Analysis of adatom attachment fluxes as well as limiting values of adatom densities at step edges for nonuniform deposition scenarios allows determination of both permeability and kinetic coefficients. Behavior of these quantities is assessedmore » as a function of key system parameters including kink density, step attachment barriers, and the step edge diffusion rate.« less

Crystallization by Particle Attachment in Synthetic, Biogenic, and Geologic Environments

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

De Yoreo, James J.; Gilbert, Pupa U.; Sommerdijk, Nico

Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. These non-classical pathways to crystallization are diverse, in contrast to classical models that consider the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle attachment processes and show that multiple pathways result from the interplay of free energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects; particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemblemore » behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems and patterns of mineralization in natural environments.« less

Dynamic analysis of fixed-free single-walled carbon nanotube-based bio-sensors because of various viruses.

PubMed

Gupta, A; Joshi, A Y; Sharma, S C; Harsha, S P

2012-09-01

In the present study, the vibrations of the fixed-free single-walled carbon nanotube (SWCNT) with attached bacterium/virus on the tip have been investigated. To explore the suitability of the SWCNT as a bacterium/virus detector device, first the various types of virus have been taken for the study and then the resonant frequencies of fixed-free SWCNT with attachment of those viruses have been simulated. These resonant frequencies are compared with the published analytical data, and it is shown that the finite element method (FEM) simulation results are in good agreement with the analytical data. The results showed the sensitivity and suitability of the SWCNT having different length and different masses (attached at the tip SWCNT) to identify the bacterium or virus.

Permeability and kinetic coefficients for mesoscale BCF surface step dynamics: Discrete two-dimensional deposition-diffusion equation analysis

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

Zhao, Renjie; Evans, James W.; Oliveira, Tiago J.

Here, a discrete version of deposition-diffusion equations appropriate for description of step flow on a vicinal surface is analyzed for a two-dimensional grid of adsorption sites representing the stepped surface and explicitly incorporating kinks along the step edges. Model energetics and kinetics appropriately account for binding of adatoms at steps and kinks, distinct terrace and edge diffusion rates, and possible additional barriers for attachment to steps. Analysis of adatom attachment fluxes as well as limiting values of adatom densities at step edges for nonuniform deposition scenarios allows determination of both permeability and kinetic coefficients. Behavior of these quantities is assessedmore » as a function of key system parameters including kink density, step attachment barriers, and the step edge diffusion rate.« less

The life and miracles of kinetochores

PubMed Central

Santaguida, Stefano; Musacchio, Andrea

2009-01-01

Kinetochores are large protein assemblies built on chromosomal loci named centromeres. The main functions of kinetochores can be grouped under four modules. The first module, in the inner kinetochore, contributes a sturdy interface with centromeric chromatin. The second module, the outer kinetochore, contributes a microtubule-binding interface. The third module, the spindle assembly checkpoint, is a feedback control mechanism that monitors the state of kinetochore–microtubule attachment to control the progression of the cell cycle. The fourth module discerns correct from improper attachments, preventing the stabilization of the latter and allowing the selective stabilization of the former. In this review, we discuss how the molecular organization of the four modules allows a dynamic integration of kinetochore–microtubule attachment with the prevention of chromosome segregation errors and cell-cycle progression. PMID:19629042

Attachment-security prime effect on skin-conductance synchronization in psychotherapists: An empirical study.

PubMed

Palmieri, Arianna; Kleinbub, Johann R; Calvo, Vincenzo; Benelli, Enrico; Messina, Irene; Sambin, Marco; Voci, Alberto

2018-03-01

Physiological synchronization (PS) is a phenomenon of simultaneous activity between two persons' physiological signals. It has been associated with empathy, shared affectivity, and efficacious therapeutic relationships. The aim of the present study was to explore the possible connections between PS and the attachment system, seeking preliminary evidence of this link by means of an experimental manipulation of the sense of attachment security in psychotherapists according to a protocol by Mikulincer and Shaver (2001), which has been proven to elicit empathetic behavior. We compared the synchronization of skin-conductance signals in brief psychological interviews between 18 psychodynamic therapists and 18 healthy volunteers. A sense of attachment-security priming was administered to half of the therapists, whereas the other half received a positive-affect control prime. Lag analysis was performed to investigate the "leading" or "following" attitudes of the participants in the two conditions. Mixed-model regressions and evidence-ratio model comparisons were used to investigate the effects of the manipulation on PS. Therapist attachment anxiety and avoidance traits were considered covariates. The attachment-security prime showed a significant effect on PS lag dynamics, but not on overall PS amount. Lag analysis showed that the therapists in the attachment-security condition were significantly more prone to assume a leading attitude in the physiological coupling than the therapists in the control condition. Therapist attachment anxiety and avoidance had no apparent effect. Our result paves the way for further exploration of the clinical relationship from a physiological standpoint. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Rheology of Membrane-Attached Minimal Actin Cortices.

PubMed

Nöding, Helen; Schön, Markus; Reinermann, Corinna; Dörrer, Nils; Kürschner, Aileen; Geil, Burkhard; Mey, Ingo; Heussinger, Claus; Janshoff, Andreas; Steinem, Claudia

2018-04-26

The actin cortex is a thin cross-linked network attached to the plasma membrane, which is responsible for the cell's shape during migration, division, and growth. In a reductionist approach, we created a minimal actin cortex (MAC) attached to a lipid membrane to correlate the filamentous actin architecture with its viscoelastic properties. The system is composed of a supported 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine bilayer doped with the receptor lipid phosphatidylinositol(4,5)-bisphosphate (PtdIns(4,5)P 2 ) to which a constitutively active mutant of ezrin, which is a direct membrane-cytoskeleton linker, is bound. The formation of the MAC on the supported lipid bilayer is analyzed as a function of increasing PtdIns(4,5)P 2 /ezrin pinning points, revealing an increase in the intersections between actin filaments, that is, the node density of the MAC. Bead tracking microrheology on the membrane-attached actin network provides information about its viscoelastic properties. The results show that ezrin serves as a dynamic cross-linker for the actin cortex attached to the lipid bilayer and that the stiffness of the network is influenced by the pinning point density, relating the plateau storage modulus G 0 to the node density of the MAC.

Mps1 Regulates Kinetochore-Microtubule Attachment Stability via the Ska Complex to Ensure Error-Free Chromosome Segregation.

PubMed

Maciejowski, John; Drechsler, Hauke; Grundner-Culemann, Kathrin; Ballister, Edward R; Rodriguez-Rodriguez, Jose-Antonio; Rodriguez-Bravo, Veronica; Jones, Mathew J K; Foley, Emily; Lampson, Michael A; Daub, Henrik; McAinsh, Andrew D; Jallepalli, Prasad V

2017-04-24

The spindle assembly checkpoint kinase Mps1 not only inhibits anaphase but also corrects erroneous attachments that could lead to missegregation and aneuploidy. However, Mps1's error correction-relevant substrates are unknown. Using a chemically tuned kinetochore-targeting assay, we show that Mps1 destabilizes microtubule attachments (K fibers) epistatically to Aurora B, the other major error-correcting kinase. Through quantitative proteomics, we identify multiple sites of Mps1-regulated phosphorylation at the outer kinetochore. Substrate modification was microtubule sensitive and opposed by PP2A-B56 phosphatases that stabilize chromosome-spindle attachment. Consistently, Mps1 inhibition rescued K-fiber stability after depleting PP2A-B56. We also identify the Ska complex as a key effector of Mps1 at the kinetochore-microtubule interface, as mutations that mimic constitutive phosphorylation destabilized K fibers in vivo and reduced the efficiency of the Ska complex's conversion from lattice diffusion to end-coupled microtubule binding in vitro. Our results reveal how Mps1 dynamically modifies kinetochores to correct improper attachments and ensure faithful chromosome segregation. Copyright © 2017 Elsevier Inc. All rights reserved.

Analysis of the effect of attachment point bias during large space debris removal using a tethered space tug

NASA Astrophysics Data System (ADS)

Chu, Zhongyi; Di, Jingnan; Cui, Jing

2017-10-01

Space debris occupies a valuable orbital resource and is an inevitable and urgent problem, especially for large space debris because of its high risk and the possible crippling effects of a collision. Space debris has attracted much attention in recent years. A tethered system used in an active debris removal scenario is a promising method to de-orbit large debris in a safe manner. In a tethered system, the flexibility of the tether used in debris removal can possibly induce tangling, which is dangerous and should be avoided. In particular, attachment point bias due to capture error can significantly affect the motion of debris relative to the tether and increase the tangling risk. Hence, in this paper, the effect of attachment point bias on the tethered system is studied based on a dynamic model established based on a Newtonian approach. Next, a safety metric of avoiding a tangle when a tether is tensioned with attachment point bias is designed to analyse the tangling risk of the tethered system. Finally, several numerical cases are established and simulated to validate the effects of attachment point bias on a space tethered system.

The role of sexual expectancies of substance use as a mediator between adult attachment and drug use among gay and bisexual men

PubMed Central

Starks, Tyrel J.; Millar, Brett M.; Tuck, Andrew N.; Wells, Brooke E.

2015-01-01

Background Research exploring substance use in gay and bisexual men has increasingly paid attention to interpersonal dynamics and relational concerns associated with the use of substances. The current study explored the role of adult attachment style on drug use as well as the potential mediating role of sexual expectancies of substance use among gay and bisexual men. Methods Online survey data were gathered from 122 gay and bisexual men across the U.S., with a mean age of 33 years of age. All participants were HIV-negative and identified their relationship status as single. Survey measures included attachment style, sexual expectancies of substance use, and recent drug use. Results While neither anxious or avoidant attachment were directly associated with the odds of recent drug use, they were positively associated with sexual expectancies of substance use (β = .27, p < .01, and β = .21, p < .05) which, in turn, were positively associated with the odds of drug use (expB = 1.09, p < .01). Bootstrapping tests of indirect effects revealed a significant indirect relationship between anxious attachment and drug use through sexual expectancies of substance use (β = .11, p < .05), but not for avoidant attachment. Conclusions This study highlights the importance of interpersonal expectancies as motivators for drug use among gay and bisexual men. Sexual expectancies of substance use were associated with drug use and anxious adult attachment was associated indirectly with drug use through these sexual expectancies. PMID:26051159

The Structure and Dynamics of the Solar Corona

NASA Technical Reports Server (NTRS)

Mikic, Zoran

2000-01-01

This report covers technical progress during the third year of the NASA Space Physics Theory contract "The Structure and Dynamics of the Solar Corona," between NASA and Science Applications International Corporation, and covers the period June 16, 1998 to August 15, 1999. This is also the final report for this contract. Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model. During the three-year duration of this contract we have published 49 articles in the scientific literature. These publications are listed in Section 3 of this report. In the Appendix we have attached reprints of selected articles. We summarize our progress during the third year of the contract. Full descriptions of our work can be found in the cited publications, a few of which are attached to this report.

Two-year-olds with autism orient to non-social contingencies rather than biological motion.

PubMed

Klin, Ami; Lin, David J; Gorrindo, Phillip; Ramsay, Gordon; Jones, Warren

2009-05-14

Typically developing human infants preferentially attend to biological motion within the first days of life. This ability is highly conserved across species and is believed to be critical for filial attachment and for detection of predators. The neural underpinnings of biological motion perception are overlapping with brain regions involved in perception of basic social signals such as facial expression and gaze direction, and preferential attention to biological motion is seen as a precursor to the capacity for attributing intentions to others. However, in a serendipitous observation, we recently found that an infant with autism failed to recognize point-light displays of biological motion, but was instead highly sensitive to the presence of a non-social, physical contingency that occurred within the stimuli by chance. This observation raised the possibility that perception of biological motion may be altered in children with autism from a very early age, with cascading consequences for both social development and the lifelong impairments in social interaction that are a hallmark of autism spectrum disorders. Here we show that two-year-olds with autism fail to orient towards point-light displays of biological motion, and their viewing behaviour when watching these point-light displays can be explained instead as a response to non-social, physical contingencies--physical contingencies that are disregarded by control children. This observation has far-reaching implications for understanding the altered neurodevelopmental trajectory of brain specialization in autism.

Small-sized and contacting Pt-WC nanostructures on graphene as highly efficient anode catalysts for direct methanol fuel cells.

PubMed

Wang, Ruihong; Xie, Ying; Shi, Keying; Wang, Jianqiang; Tian, Chungui; Shen, Peikang; Fu, Honggang

2012-06-11

The synergistic effect between Pt and WC is beneficial for methanol electro-oxidation, and makes Pt-WC catalyst a promising anode candidate for the direct methanol fuel cell. This paper reports on the design and synthesis of small-sized and contacting Pt-WC nanostructures on graphene that bring the synergistic effect into full play. Firstly, DFT calculations show the existence of a strong covalent interaction between WC and graphene, which suggests great potential for anchoring WC on graphene with formation of small-sized, well-dispersed WC particles. The calculations also reveal that, when Pt attaches to the pre-existing WC/graphene hybrid, Pt particles preferentially grow on WC rather than graphene. Our experiments confirmed that highly disperse WC nanoparticles (ca. 5 nm) can indeed be anchored on graphene. Also, Pt particles 2-3 nm in size are well dispersed on WC/graphene hybrid and preferentially grow on WC grains, forming contacting Pt-WC nanostructures. These results are consistent with the theoretical findings. X-ray absorption fine structure spectroscopy further confirms the intimate contact between Pt and WC, and demonstrates that the presence of WC can facilitate the crystallinity of Pt particles. This new Pt-WC/graphene catalyst exhibits a high catalytic efficiency toward methanol oxidation, with a mass activity 1.98 and 4.52 times those of commercial PtRu/C and Pt/C catalysts, respectively. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two-year-olds with autism orient to nonsocial contingencies rather than biological motion

PubMed Central

Klin, Ami; Lin, David J.; Gorrindo, Phillip; Ramsay, Gordon; Jones, Warren

2009-01-01

Typically-developing human infants preferentially attend to biological motion within the first days of life1. This ability is highly conserved across species2,3 and is believed to be critical for filial attachment and for detection of predators4. The neural underpinnings of biological motion perception are overlapping with brain regions involved in perception of basic social signals such as facial expression and gaze direction5, and preferential attention to biological motion is seen as a precursor to the capacity for attributing intentions to others6. However, in a serendipitous observation7, we recently found that an infant with autism failed to recognize point-light displays of biological motion but was instead highly sensitive to the presence of a non-social, physical contingency that occurred within the stimuli by chance. This observation raised the hypothesis that perception of biological motion may be altered in children with autism from a very early age, with cascading consequences for both social development and for the lifelong impairments in social interaction that are a hallmark of autism spectrum disorders8. Here we show that two-year-olds with autism fail to orient towards point-light displays of biological motion, and that their viewing behavior when watching these point-light displays can be explained instead as a response to non-social, physical contingencies physical contingencies that are disregarded by control children. This observation has far-reaching implications for understanding the altered neurodevelopmental trajectory of brain specialization in autism9. PMID:19329996

Assured crew return vehicle post landing configuration design and test

NASA Technical Reports Server (NTRS)

1992-01-01

The 1991-1992 senior Mechanical and Aerospace Engineering Design class continued work on the post landing configurations for the Assured Crew Return Vehicle (ACRV) and the Emergency Egress Couch (EEC). The ACRV will be permanently docked to Space Station Freedom fulfilling NASA's commitment of Assured Crew Return Capability in the event of an accident or illness aboard Space Station Freedom. The EEC provides medical support and a transportation surface for an incapacitated crew member. The objective of the projects was to give the ACRV Project Office data to feed into their feasibility studies. Four design teams were given the task of developing models with dynamically and geometrically scaled characteristics. Groups one and two combined efforts to design a one-fifth scale model for the Apollo Command Module derivative, an on-board flotation system, and a lift attachment point system. This model was designed to test the feasibility of a rigid flotation and stabilization system and to determine the dynamics associated with lifting the vehicle during retrieval. However, due to priorities, it was not built. Group three designed a one-fifth scale model of the Johnson Space Center (JSC) benchmark configuration, the Station Crew Return Alternative Module (SCRAM) with a lift attachment point system. This model helped to determine the flotation and lifting characteristics of the SCRAM configuration. Group four designed a full scale EEC with changeable geometric and geometric and dynamic characteristics. This model provided data on the geometric characteristics of the EEC and on the placement of the CG and moment of inertia. It also gave the helicopter rescue personnel direct input to the feasibility study. Section 1 describes in detail the design of a one-fifth scale model of the Apollo Command Module Derivative (ACMD) ACRV. The objective of the ACMD Configuration Model Team was to use geometric and dynamic constraints to design a one-fifth scale working model of the Apollo Command Module Derivative (ACMD) configuration with a Lift Attachment Point (LAP) System. This model was required to incorporate a rigidly mounted flotation system and the egress system designed the previous academic year. The LAP system was to be used to determine the dynamic effects of locating the lifting points at different locations on the vehicle. The team was then to build and test the model; however, due to priorities, this did not occur. To better simulate the ACMD after a water landing, the nose cone section was removed and the deck area exposed. The areas researched during the design process were construction, center of gravity and moment of inertia, and lift attachment points.

Characterization of return flow pathways during flood irrigation

NASA Astrophysics Data System (ADS)

Claes, N.; Paige, G. B.; Parsekian, A.; Gordon, B. L.; Miller, S. N.

2015-12-01

With a decline in water resources available for private consumption and irrigation, the importance of sustainable water management practices is increasing. Local management decisions, based on models may affect the availability of water both locally and downstream, causing a ripple effect. It is therefore important that the models that these local management decisions are based on, accurately quantify local hydrological processes and the timescales at which they happen. We are focusing on return flow from flood irrigation, which can occur via different pathways back to the streams: overland flow, near-surface return flow and return flow via pathways below the vadose zone. The question addressed is how these different pathways each contribute to the total amount of return flow and the dynamics behind them. We used time-lapse ERT measurements in combination with an ensemble of ERT and seismic lines to answer this question via (1) capturing the process of gradual fragmentation of aqueous environments in the vadose zone during drying stages at field scale; (2) characterization of the formation of preferential flow paths from infiltrating wetting fronts during wetting cycles at field scale. The time-lapse ERT provides the possibility to capture the dynamic processes involved during the occurrence of finger flow or macro-pores when an intensive wetting period during flood irrigation occurs. It elucidates the dynamics of retention in the vadose zone during drying and wetting periods at field scale. This method provides thereby a link to upscale from laboratory experiments to field scale and watershed scale for finger flow and preferential flow paths and illustrates the hysteresis behavior at field scale.

Synthesis of Multishell Nanoplates by Consecutive Epitaxial Growth of Bi2Se3 and Bi2Te3 Nanoplates and Enhanced Thermoelectric Properties.

PubMed

Min, Yuho; Park, Gyeongbae; Kim, Bongsoo; Giri, Anupam; Zeng, Jie; Roh, Jong Wook; Kim, Sang Il; Lee, Kyu Hyoung; Jeong, Unyong

2015-07-28

We herein demonstrate the successive epitaxial growth of Bi2Te3 and Bi2Se3 on seed nanoplates for the scalable synthesis of heterostructured nanoplates (Bi2Se3@Bi2Te3) and multishell nanoplates (Bi2Se3@Bi2Te3@Bi2Se3, Bi2Se3@Bi2Te3@Bi2Se3@Bi2Te3). The relative dimensions of the constituting layers are controllable via the molar ratios of the precursors added to the seed nanoplate solution. Reduction of the precursors produces nanoparticles that attach preferentially to the sides of the seed nanoplates. Once attached, the nanoparticles reorganize epitaxially on the seed crystal lattices to form single-crystalline core-shell nanoplates. The nanoplates, initially 100 nm wide, grew laterally to 620 nm in the multishell structure, while their thickness increased more moderately, from 5 to 20 nm. The nanoplates were pelletized into bulk samples by spark plasma sintering and their thermoelectric properties are compared. A peak thermoelectric figure of merit (ZT) ∼0.71 was obtained at 450 K for the bulk of Bi2Se3@Bi2Te3 nanoplates by simultaneous modulation of electronic and thermal transport in the presence of highly dense grain and phase boundaries.

West Nile virus discriminates between DC-SIGN and DC-SIGNR for cellular attachment and infection.

PubMed

Davis, Carl W; Nguyen, Hai-Yen; Hanna, Sheri L; Sánchez, Melissa D; Doms, Robert W; Pierson, Theodore C

2006-02-01

The C-type lectins DC-SIGN and DC-SIGNR bind mannose-rich glycans with high affinity. In vitro, cells expressing these attachment factors efficiently capture, and are infected by, a diverse array of appropriately glycosylated pathogens, including dengue virus. In this study, we investigated whether these lectins could enhance cellular infection by West Nile virus (WNV), a mosquito-borne flavivirus related to dengue virus. We discovered that DC-SIGNR promoted WNV infection much more efficiently than did DC-SIGN, particularly when the virus was grown in human cell types. The presence of a single N-linked glycosylation site on either the prM or E glycoprotein of WNV was sufficient to allow DC-SIGNR-mediated infection, demonstrating that uncleaved prM protein present on a flavivirus virion can influence viral tropism under certain circumstances. Preferential utilization of DC-SIGNR was a specific property conferred by the WNV envelope glycoproteins. Chimeras between DC-SIGN and DC-SIGNR demonstrated that the ability of DC-SIGNR to promote WNV infection maps to its carbohydrate recognition domain. WNV virions and subviral particles bound to DC-SIGNR with much greater affinity than DC-SIGN. We believe this is the first report of a pathogen interacting more efficiently with DC-SIGNR than with DC-SIGN. Our results should lead to the discovery of new mechanisms by which these well-studied lectins discriminate among ligands.

Smooth muscle membrane organization in the normal and dysfunctional human urinary bladder: a structural analysis.

PubMed

Burkhard, Fiona C; Monastyrskaya, Katia; Studer, Urs E; Draeger, Annette

2005-01-01

The decline in contractile properties is a characteristic feature of the dysfunctional bladder as a result of infravesical outlet obstruction. During clinical progression of the disease, smooth muscle cells undergo structural modifications. Since adaptations to constant changes in length require a high degree of structural organization within the sarcolemma, we have investigated the expression of several proteins, which are involved in smooth muscle membrane organization, in specimens derived from normal and dysfunctional organs. Specimen from patients with urodynamically normal/equivocal (n = 4), obstructed (n = 2), and acontractile (n = 2) bladders were analyzed relative to their structural features and sarcolemmal protein profile. Smooth muscle cells within the normal urinary bladder display a distinct sarcolemmal domain structure, characterized by firm actin-attachment sites, alternating with flexible "hinge" regions. In obstructed bladders, foci of cells displaying degenerative sarcolemmal changes alternate with areas of hypertrophic cells in which the membrane appears unaffected. In acontractile organs, the overall membrane structure remains intact, however annexin 6, a protein belonging to a family of Ca2+-dependent, "membrane-organizers," is downregulated. Degenerative changes in smooth muscle cells, which are chronically working against high resistance, are preferentially located within the actin-attachment sites. In acontractile bladders, the downregulation of annexin 6 might have a bearing on the fine-tuning of the plasma membrane during contraction/relaxation cycles. Copyright 2005 Wiley-Liss, Inc.

Dynamic bioactive stimuli-responsive polymeric surfaces

NASA Astrophysics Data System (ADS)

Pearson, Heather Marie

This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of --COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface anticoagulant attributes, PE and PTFE surfaces were functionalized with pH-responsive poly(2-vinyl pyridine) (P2VP) and poly(acrylic acid) (PAA) polyelectrolyte tethers terminated with NH2 and COOH groups. The goal of these studies was to develop switchable stimuli-responsive polymeric surfaces that interact with biological environments and display simultaneous antimicrobial and anticoagulant properties. Antimicrobial AMP was covalently attached to --COOH terminal ends of protected PAA, while anticoagulant heparin (HEP) was attached to terminal --NH2 groups of P2VP. When pH < 2.3, the P2VP segments are protonated and extend, but for pH > 5.5, they collapse while the PAA segments extend. Such surfaces, when exposed to Staphylococcus aureus, inhibit bacterial growth due to the presence of AMP, as well as are effective anticoagulants due to the presence of covalently attached HEP. Comparison of these "dynamic" pH responsive surfaces with "static" surfaces terminated with AMP entities show significant enhancement of longevity and surface activity against microbial film formation. The last portion of this dissertation focuses on the covalent attachment of living T1 and Φ11 bacteriophages (phages) on PE and PTFE surface. This was accomplished by carbodiimide coupling between --COOH groups on PE and PTFE surfaces and --NH2 moieties present on T1 and Φ11 phages. These studies show that covalently attached T1 and Φ11 phages retain their antimicrobial activity manifested by the effective destruction of both Gram negative Escherichia coli (Φ11) phages and Gram positive Staphylococcus aureus bacteria (T1).

Global ecosystem dynamics investigation (GEDI) LiDAR sampling strategy

Treesearch

Paul L. Patterson; Sean Healey

2015-01-01

Global Ecosystem Dynamics Investigation (GEDI) Lidar was selected by NASA for funding under its Earth Venture Instrument-2 program. A full-waveform lidar instrument will be attached to the International Space Station (ISS) and will provide unprecedented detail about the structure of the world’s forest between 52°S and 52°N (the area covered by the ISS ground track)....

Simulational nanoengineering: Molecular dynamics implementation of an atomistic Stirling engine.

PubMed

Rapaport, D C

2009-04-01

A nanoscale-sized Stirling engine with an atomistic working fluid has been modeled using molecular dynamics simulation. The design includes heat exchangers based on thermostats, pistons attached to a flywheel under load, and a regenerator. Key aspects of the behavior, including the time-dependent flows, are described. The model is shown to be capable of stable operation while producing net work at a moderate level of efficiency.

A durable and biocompatible ascorbic acid-based covalent coating method of polydimethylsiloxane for dynamic cell culture.

PubMed

Leivo, Joni; Virjula, Sanni; Vanhatupa, Sari; Kartasalo, Kimmo; Kreutzer, Joose; Miettinen, Susanna; Kallio, Pasi

2017-07-01

Polydimethylsiloxane (PDMS) is widely used in dynamic biological microfluidic applications. As a highly hydrophobic material, native PDMS does not support cell attachment and culture, especially in dynamic conditions. Previous covalent coating methods use glutaraldehyde (GA) which, however, is cytotoxic. This paper introduces a novel and simple method for binding collagen type I covalently on PDMS using ascorbic acid (AA) as a cross-linker instead of GA. We compare the novel method against physisorption and GA cross-linker-based methods. The coatings are characterized by immunostaining, contact angle measurement, atomic force microscopy and infrared spectroscopy, and evaluated in static and stretched human adipose stem cell (hASC) cultures up to 13 days. We found that AA can replace GA as a cross-linker in the covalent coating method and that the coating is durable after sonication and after 6 days of stretching. Furthermore, we show that hASCs attach and proliferate better on AA cross-linked samples compared with physisorbed or GA-based methods. Thus, in this paper, we provide a new PDMS coating method for studying cells, such as hASCs, in static and dynamic conditions. The proposed method is an important step in the development of PDMS-based devices in cell and tissue engineering applications. © 2017 The Author(s).

Static and (quasi)dynamic calibration of stroboscopic scanning white light interferometer

NASA Astrophysics Data System (ADS)

Seppä, Jeremias; Kassamakov, Ivan; Nolvi, Anton; Heikkinen, Ville; Paulin, Tor; Lassila, Antti; Hao, Ling; Hæggsröm, Edward

2013-04-01

A scanning white light interferometer can characterize out of plane features and motion in M(N)EMS devices. Like any other form and displacement measuring instrument, the scanning interferometer results should be linked to the metre definition to be comparable and unambiguous. Traceability is built up by careful error characterization and calibration of the interferometer. The main challenge in this calibration is to have a reference device producing accurate and reproducible dynamic out-of-plane displacement when submitted to standard loads. We use a flat mirror attached to a piezoelectric transducer for static and (quasi)dynamic calibration of a stroboscopic scanning light interferometer. First we calibrated the piezo-scanned flexure guided transducer stage using a symmetric differential heterodyne laser interferometer developed at the Centre for Metrology and Accreditation (MIKES). The standard uncertainty of the piezo stage motion calibration was 3.0 nm. Then we used the piezo-stage as a transfer standard to calibrate our stroboscopic interferometer whose light source was pulsed at 200 Hz and 400 Hz with 0.5% duty cycle. We measured the static position and (quasi)dynamic motion of the attached mirror relative to a reference surface. This methodology permits calibrating the vertical scale of the stroboscopic scanning white light interferometer.

Partitioning dynamics of unsaturated flows in fractured porous media: Laboratory studies and three-dimensional multi-scale smoothed particle hydrodynamics simulations of gravity-driven flow in fractures

NASA Astrophysics Data System (ADS)

Kordilla, J.; Bresinsky, L. T.; Shigorina, E.; Noffz, T.; Dentz, M.; Sauter, M.; Tartakovsky, A. M.

2017-12-01

Preferential flow dynamics in unsaturated fractures remain a challenging topic on various scales. On pore- and fracture-scales the highly erratic gravity-driven flow dynamics often provoke a strong deviation from classical volume-effective approaches. Against the common notion that flow in fractures (or macropores) can only occur under equilibrium conditions, i.e., if the surrounding porous matrix is fully saturated and capillary pressures are high enough to allow filling of the fracture void space, arrival times suggest the existence of rapid preferential flow along fractures, fracture networks, and fault zones, even if the matrix is not fully saturated. Modeling such flows requires efficient numerical techniques to cover various flow-relevant physics, such as surface tension, static and dynamic contact angles, free-surface (multi-phase) interface dynamics, and formation of singularities. Here we demonstrate the importance of such flow modes on the partitioning dynamics at simple fracture intersections, with a combination of laboratory experiments, analytical solutions and numerical simulations using our newly developed massively parallel smoothed particle hydrodynamics (SPH) code. Flow modes heavily influence the "bypass" behavior of water flowing along a fracture junction. Flows favoring the formation of droplets exhibit a much stronger bypass capacity compared to rivulet flows, where nearly the whole fluid mass is initially stored within the horizontal fracture. This behavior is demonstrated for a multi-inlet laboratory setup where the inlet-specific flow rate is chosen so that either a droplet or rivulet flow persists. The effect of fluid buffering within the horizontal fracture is presented in terms of dimensionless fracture inflow so that characteristic scaling regimes can be recovered. For both cases (rivulets and droplets), flow within the horizontal fracture transitions into a Washburn regime until a critical threshold is reached and the bypass efficiency increases. For rivulet flows, the initial filling of the horizontal fracture is described by classical plug flow. Meanwhile, for droplet flows, a size-dependent partitioning behavior is observed, and the filling of the fracture takes longer.

Mechanisms of extracellular S0 globule production and degradation in Chlorobaculum tepidum via dynamic cell–globule interactions

PubMed Central

Marnocha, C. L.; Levy, A. T.; Powell, D. H.; Hanson, T. E.

2016-01-01

The Chlorobiales are anoxygenic phototrophs that produce solid, extracellular elemental sulfur globules as an intermediate step in the oxidation of sulfide to sulfate. These organisms must export sulfur while preventing cell encrustation during S0 globule formation; during globule degradation they must find and mobilize the sulfur for intracellular oxidation to sulfate. To understand how the Chlorobiales address these challenges, we characterized the spatial relationships and physical dynamics of Chlorobaculum tepidum cells and S0 globules by light and electron microscopy. Cba. tepidum commonly formed globules at a distance from cells. Soluble polysulfides detected during globule production may allow for remote nucleation of globules. Polysulfides were also detected during globule degradation, probably produced as an intermediate of sulfur oxidation by attached cells. Polysulfides could feed unattached cells, which made up over 80% of the population and had comparable growth rates to attached cells. Given that S0 is formed remotely from cells, there is a question as to how cells are able to move toward S0 in order to attach. Time-lapse microscopy shows that Cba. tepidum is in fact capable of twitching motility, a finding supported by the presence of genes encoding type IV pili. Our results show how Cba. tepidum is able to avoid mineral encrustation and benefit from globule degradation even when not attached. In the environment, Cba. tepidum may also benefit from soluble sulfur species produced by other sulfur-oxidizing or sulfur-reducing bacteria as these organisms interact with its biogenic S0 globules. PMID:27121868

Weighted Scaling in Non-growth Random Networks

NASA Astrophysics Data System (ADS)

Chen, Guang; Yang, Xu-Hua; Xu, Xin-Li

2012-09-01

We propose a weighted model to explain the self-organizing formation of scale-free phenomenon in non-growth random networks. In this model, we use multiple-edges to represent the connections between vertices and define the weight of a multiple-edge as the total weights of all single-edges within it and the strength of a vertex as the sum of weights for those multiple-edges attached to it. The network evolves according to a vertex strength preferential selection mechanism. During the evolution process, the network always holds its total number of vertices and its total number of single-edges constantly. We show analytically and numerically that a network will form steady scale-free distributions with our model. The results show that a weighted non-growth random network can evolve into scale-free state. It is interesting that the network also obtains the character of an exponential edge weight distribution. Namely, coexistence of scale-free distribution and exponential distribution emerges.

Scaling of load in communications networks.

PubMed

Narayan, Onuttom; Saniee, Iraj

2010-09-01

We show that the load at each node in a preferential attachment network scales as a power of the degree of the node. For a network whose degree distribution is p(k)∼k{-γ} , we show that the load is l(k)∼k{η} with η=γ-1 , implying that the probability distribution for the load is p(l)∼1/l{2} independent of γ . The results are obtained through scaling arguments supported by finite size scaling studies. They contradict earlier claims, but are in agreement with the exact solution for the special case of tree graphs. Results are also presented for real communications networks at the IP layer, using the latest available data. Our analysis of the data shows relatively poor power-law degree distributions as compared to the scaling of the load versus degree. This emphasizes the importance of the load in network analysis.

A mixing evolution model for bidirectional microblog user networks

NASA Astrophysics Data System (ADS)

Yuan, Wei-Guo; Liu, Yun

2015-08-01

Microblogs have been widely used as a new form of online social networking. Based on the user profile data collected from Sina Weibo, we find that the number of microblog user bidirectional friends approximately corresponds with the lognormal distribution. We then build two microblog user networks with real bidirectional relationships, both of which have not only small-world and scale-free but also some special properties, such as double power-law degree distribution, disassortative network, hierarchical and rich-club structure. Moreover, by detecting the community structures of the two real networks, we find both of their community scales follow an exponential distribution. Based on the empirical analysis, we present a novel evolution network model with mixed connection rules, including lognormal fitness preferential and random attachment, nearest neighbor interconnected in the same community, and global random associations in different communities. The simulation results show that our model is consistent with real network in many topology features.

A Novel BA Complex Network Model on Color Template Matching

PubMed Central

Han, Risheng; Yue, Guangxue; Ding, Hui

2014-01-01

A novel BA complex network model of color space is proposed based on two fundamental rules of BA scale-free network model: growth and preferential attachment. The scale-free characteristic of color space is discovered by analyzing evolving process of template's color distribution. And then the template's BA complex network model can be used to select important color pixels which have much larger effects than other color pixels in matching process. The proposed BA complex network model of color space can be easily integrated into many traditional template matching algorithms, such as SSD based matching and SAD based matching. Experiments show the performance of color template matching results can be improved based on the proposed algorithm. To the best of our knowledge, this is the first study about how to model the color space of images using a proper complex network model and apply the complex network model to template matching. PMID:25243235

A novel BA complex network model on color template matching.

PubMed

Han, Risheng; Shen, Shigen; Yue, Guangxue; Ding, Hui

2014-01-01

A novel BA complex network model of color space is proposed based on two fundamental rules of BA scale-free network model: growth and preferential attachment. The scale-free characteristic of color space is discovered by analyzing evolving process of template's color distribution. And then the template's BA complex network model can be used to select important color pixels which have much larger effects than other color pixels in matching process. The proposed BA complex network model of color space can be easily integrated into many traditional template matching algorithms, such as SSD based matching and SAD based matching. Experiments show the performance of color template matching results can be improved based on the proposed algorithm. To the best of our knowledge, this is the first study about how to model the color space of images using a proper complex network model and apply the complex network model to template matching.

Evolution of the most common English words and phrases over the centuries.

PubMed

Perc, Matjaz

2012-12-07

By determining the most common English words and phrases since the beginning of the sixteenth century, we obtain a unique large-scale view of the evolution of written text. We find that the most common words and phrases in any given year had a much shorter popularity lifespan in the sixteenth century than they had in the twentieth century. By measuring how their usage propagated across the years, we show that for the past two centuries, the process has been governed by linear preferential attachment. Along with the steady growth of the English lexicon, this provides an empirical explanation for the ubiquity of Zipf's law in language statistics and confirms that writing, although undoubtedly an expression of art and skill, is not immune to the same influences of self-organization that are known to regulate processes as diverse as the making of new friends and World Wide Web growth.

Analyses of Interactions Between Heparin and the Apical Surface Proteins of Plasmodium falciparum

NASA Astrophysics Data System (ADS)

Kobayashi, Kyousuke; Takano, Ryo; Takemae, Hitoshi; Sugi, Tatsuki; Ishiwa, Akiko; Gong, Haiyan; Recuenco, Frances C.; Iwanaga, Tatsuya; Horimoto, Taisuke; Akashi, Hiroomi; Kato, Kentaro

2013-11-01

Heparin, a sulfated glycoconjugate, reportedly inhibits the blood-stage growth of the malaria parasite Plasmodium falciparum. Elucidation of the inhibitory mechanism is valuable for developing novel invasion-blocking treatments based on heparin. Merozoite surface protein 1 has been reported as a candidate target of heparin; however, to better understand the molecular mechanisms involved, we characterized the molecules that bind to heparin during merozoite invasion. Here, we show that heparin binds only at the apical tip of the merozoite surface and that multiple heparin-binding proteins localize preferentially in the apical organelles. To identify heparin-binding proteins, parasite proteins were fractionated by means of heparin affinity chromatography and subjected to immunoblot analysis with ligand-specific antibodies. All tested members of the Duffy and reticulocyte binding-like families bound to heparin with diverse affinities. These findings suggest that heparin masks the apical surface of merozoites and blocks interaction with the erythrocyte membrane after initial attachment.

Exact solution for the time evolution of network rewiring models

NASA Astrophysics Data System (ADS)

Evans, T. S.; Plato, A. D. K.

2007-05-01

We consider the rewiring of a bipartite graph using a mixture of random and preferential attachment. The full mean-field equations for the degree distribution and its generating function are given. The exact solution of these equations for all finite parameter values at any time is found in terms of standard functions. It is demonstrated that these solutions are an excellent fit to numerical simulations of the model. We discuss the relationship between our model and several others in the literature, including examples of urn, backgammon, and balls-in-boxes models, the Watts and Strogatz rewiring problem, and some models of zero range processes. Our model is also equivalent to those used in various applications including cultural transmission, family name and gene frequencies, glasses, and wealth distributions. Finally some Voter models and an example of a minority game also show features described by our model.

Scale-free networks which are highly assortative but not small world

NASA Astrophysics Data System (ADS)

Small, Michael; Xu, Xiaoke; Zhou, Jin; Zhang, Jie; Sun, Junfeng; Lu, Jun-An

2008-06-01

Uncorrelated scale-free networks are necessarily small world (and, in fact, smaller than small world). Nonetheless, for scale-free networks with correlated degree distribution this may not be the case. We describe a mechanism to generate highly assortative scale-free networks which are not small world. We show that it is possible to generate scale-free networks, with arbitrary degree exponent γ>1 , such that the average distance between nodes in the network is large. To achieve this, nodes are not added to the network with preferential attachment. Instead, we greedily optimize the assortativity of the network. The network generation scheme is physically motivated, and we show that the recently observed global network of Avian Influenza outbreaks arises through a mechanism similar to what we present here. Simulations show that this network exhibits very similar physical characteristics (very high assortativity, clustering, and path length).

The Italian primary school-size distribution and the city-size: a complex nexus

NASA Astrophysics Data System (ADS)

Belmonte, Alessandro; di Clemente, Riccardo; Buldyrev, Sergey V.

2014-06-01

We characterize the statistical law according to which Italian primary school-size distributes. We find that the school-size can be approximated by a log-normal distribution, with a fat lower tail that collects a large number of very small schools. The upper tail of the school-size distribution decreases exponentially and the growth rates are distributed with a Laplace PDF. These distributions are similar to those observed for firms and are consistent with a Bose-Einstein preferential attachment process. The body of the distribution features a bimodal shape suggesting some source of heterogeneity in the school organization that we uncover by an in-depth analysis of the relation between schools-size and city-size. We propose a novel cluster methodology and a new spatial interaction approach among schools which outline the variety of policies implemented in Italy. Different regional policies are also discussed shedding lights on the relation between policy and geographical features.

DARPin-targeting of Measles Virus: Unique Bispecificity, Effective Oncolysis, and Enhanced Safety

PubMed Central

Friedrich, Katrin; Hanauer, Jan RH; Prüfer, Steffen; Münch, Robert C; Völker, Iris; Filippis, Christodoulos; Jost, Christian; Hanschmann, Kay-Martin; Cattaneo, Roberto; Peng, Kah-Whye; Plückthun, Andreas; Buchholz, Christian J; Cichutek, Klaus; Mühlebach, Michael D

2013-01-01

Oncolytic virotherapy is an emerging treatment modality that uses replication-competent viruses to destroy cancers. Many naturally occurring viruses have a preferential, although nonexclusive, tropism for tumors and tumor cells. In addition, specific targeting of cancer cells can be achieved at the virus entry level. We optimized retargeting of cell entry by elongating the measles virus attachment protein with designed ankyrin repeat proteins (DARPins), while simultaneously ablating entry through the natural receptors. DARPin-targeted viruses were strongly attenuated in off-target tissue, thereby enhancing safety, but completely eliminated tumor xenografts. Taking advantage of the unique properties of DARPins of being fused without generating folding problems, we generated a virus simultaneous targeting two different tumor markers. The bispecific virus retained the original oncolytic efficacy, while providing proof of concept for a strategy to counteract issues of resistance development. Thus, DARPin-targeting opens new prospects for the development of personalized, targeted therapeutics. PMID:23380817

Effect of tidal fields on star clusters

NASA Technical Reports Server (NTRS)

Chernoff, David; Weinberg, Martin

1991-01-01

We follow the dynamical evolution of a star cluster in a galactic tidal field using a restricted N-body code. We find large asymmetric distortions in the outer profile of the cluster in the first 10 or so crossing times as material is lost. Prograde stars escape preferentially and establish a potentially observable retrograde rotation in the halo. We present the rate of particle loss and compare with the prescription proposed by Lee and Ostriker (1987).

Experimental analysis of the dynamical response of energy harvesting devices based on bistable laminated plates.

PubMed

Syta, A; Bowen, C R; Kim, H A; Rysak, A; Litak, G

The use of bistable laminates is a potential approach to realize broadband piezoelectric based energy harvesting systems. In this paper the dynamic response of a piezoelectric material attached to a bistable laminate plate is examined based on the experimental generated voltage time series. The system was subjected to harmonic excitations and exhibited single-well and snap-through vibrations of both periodic and chaotic character. To identify the dynamics of the system response we examined the frequency spectrum, bifurcation diagrams, phase portraits, and the 0-1 test.

Spatiotemporal dynamics of Aurora B-PLK1-MCAK signaling axis orchestrates kinetochore bi-orientation and faithful chromosome segregation

PubMed Central

Shao, Hengyi; Huang, Yuejia; Zhang, Liangyu; Yuan, Kai; Chu, Youjun; Dou, Zhen; Jin, Changjiang; Garcia-Barrio, Minerva; Liu, Xing; Yao, Xuebiao

2015-01-01

Chromosome segregation in mitosis is orchestrated by the dynamic interactions between the kinetochore and spindle microtubules. The microtubule depolymerase mitotic centromere-associated kinesin (MCAK) is a key regulator for an accurate kinetochore-microtubule attachment. However, the regulatory mechanism underlying precise MCAK depolymerase activity control during mitosis remains elusive. Here, we describe a novel pathway involving an Aurora B-PLK1 axis for regulation of MCAK activity in mitosis. Aurora B phosphorylates PLK1 on Thr210 to activate its kinase activity at the kinetochores during mitosis. Aurora B-orchestrated PLK1 kinase activity was examined in real-time mitosis using a fluorescence resonance energy transfer-based reporter and quantitative analysis of native PLK1 substrate phosphorylation. Active PLK1, in turn, phosphorylates MCAK at Ser715 which promotes its microtubule depolymerase activity essential for faithful chromosome segregation. Importantly, inhibition of PLK1 kinase activity or expression of a non-phosphorylatable MCAK mutant prevents correct kinetochore-microtubule attachment, resulting in abnormal anaphase with chromosome bridges. We reason that the Aurora B-PLK1 signaling at the kinetochore orchestrates MCAK activity, which is essential for timely correction of aberrant kinetochore attachment to ensure accurate chromosome segregation during mitosis. PMID:26206521

Attachment insecurity and psychological resources associated with adjustment disorders.

PubMed

Ponizovsky, Alexander M; Levov, Kathy; Schultz, Yakov; Radomislensky, Ira

2011-04-01

This study examined the adult attachment styles, interpersonal distance from potential attachment figures and strangers, coping strategies, perceived social support, and stress-related self-variables among patients diagnosed with adjustment disorders (AJD). Seventy patients at an outpatient clinic and 61 matched controls completed a battery of standardized questionnaires. Univariate and multivariate statistical analyses were used to evaluate the parameters of interest. Using attachment theory (J. Bowlby, 1988) and the dynamic stress-vulnerability model of depressive disorder (G. W. Brown & T. O. Harris, 1989) as the analytical frameworks, the authors hypothesized that participants with AJD would: (a) display more insecure attachment styles, (b) be less tolerant of close interpersonal proximity, (c) use more emotion-oriented coping strategies, (d) display lower self-efficacy and self-esteem, and (e) perceive less social support from family, friends, and significant others. We further hypothesized that these variables would be predictive of depressive symptoms. All of the hypotheses were confirmed. The results suggest that the insecure fearful-avoidant attachment style is associated with severe depressive symptoms in patients with AJD. However, other psychosocial factors, such as low self-esteem and poor social support from friends, were more predictive of AJD symptoms. The findings warrant further studies on the risk and protective effects of these factors in the development of AJD and other stress-induced disorders. © 2011 American Orthopsychiatric Association.

When the Desert Beetle Met the Carnivorous Plant: A Perfect Match for Droplet Growth and Shedding

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

Aizenberg, Joanna; Park, Kyoo Chul; Kim, Philseok

2015-01-14

Phase change of vapor followed by coalescence and transport on ubiquitous bumped or curved surfaces is of fundamental importance for a wide range of phenomena and applications from water condensation on cold beverage bottles, to fogging on glasses and windshields, self-cleaning by jumping droplets, weathering, self-assembly, desalination, latent heat transfer, etc. Over the past decades, many attempts to understand and control the droplet growth dynamics and shedding of condensates on textured surfaces have focused on finding the role of micro/nanotexture combined with wettability. In particular, inspired by the Namib desert beetle bump structure, studies tested the effect of topography onmore » the preferential condensation. However, like the preferential condensation observed on flat surfaces, hybrid wettability rather than texture plays a major role; the role of bump topography on local preferential condensation has been unexplored and still not clearly understood. In addition, given that not only facilitating the droplet growth but also transporting the condensed droplets toward the desired reservoir is essential to make fresh sites for renucleation and regrowth of the droplets for enhancing condensation efficiency, the current hybrid-wettability- based design is not efficient to transport the condensates due to the high contact angle hysteresis created by highly wettable pinning points. Here we show that beetle-inspired bump topography leads faster localized condensation and transport of water. Employing simple analytic and more complicated numerical calculations, we reveal the detailed role of topography and predict the focused diffusion flux based on the distortion of concentration gradient around convex surface topography. We experimentally demonstrate the systematic understanding on the unseen effect of topographical parameters on faster droplet growth dynamics on various bump geometries. Further rational design of asymmetric topography and synergetic combination with slippery coating simultaneously enable both faster droplet growth and transport for applications including efficient water condensation.« less

CRYSTAL GROWTH. Crystallization by particle attachment in synthetic, biogenic, and geologic environments.

PubMed

De Yoreo, James J; Gilbert, Pupa U P A; Sommerdijk, Nico A J M; Penn, R Lee; Whitelam, Stephen; Joester, Derk; Zhang, Hengzhong; Rimer, Jeffrey D; Navrotsky, Alexandra; Banfield, Jillian F; Wallace, Adam F; Michel, F Marc; Meldrum, Fiona C; Cölfen, Helmut; Dove, Patricia M

2015-07-31

Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. The particles involved in these nonclassical pathways to crystallization are diverse, in contrast to classical models that consider only the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle-attachment processes and show that multiple pathways result from the interplay of free-energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects, particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemble behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems, biominerals, and patterns of mineralization in natural environments. Copyright © 2015, American Association for the Advancement of Science.

Microscopic Behavior Of Colloidal Particles Under The Effect Of Acoustic Stimulations In The Ultrasonic To Megasonic Range

NASA Astrophysics Data System (ADS)

Abdel-Fattah, Amr I.; Roberts, Peter M.

2006-05-01

It is well known that colloid attachment and detachment at solid surfaces are influenced strongly by physico-chemical conditions controlling electric double layer (EDL) and solvation-layer effects. We present experimental observations demonstrating that, in addition, acoustic waves can produce strong effects on colloid/surface interactions that can alter the behavior of colloid and fluid transport in porous media. Microscopic colloid visualization experiments were performed with polystyrene micro-spheres suspended in water in a parallel-plate glass flow cell. When acoustic energy was applied to the cell at frequencies from 500 kHz to 5 MHz, changes in colloid attachment to and detachment from the glass cell surfaces were observed. Quantitative measurements of acoustically-induced detachment of 300-nm microspheres in 0.1M NaCl solution demonstrated that roughly 30% of the colloids that were attached to the glass cell wall during flow alone could be detached rapidly by applying acoustics at frequencies in the range of 0.7 to 1.2 MHz. The remaining attached colloids could not be detached by acoustics. This implies the existence of both "strong" and "weak" attachment sites at the cell surface. Subsequent re-attachment of colloids with acoustics turned off occurred only at new, previously unoccupied sites. Thus, acoustics appears to accelerate simultaneously both the deactivation of existing weak sites where colloids are already attached, and the activation of new weak sites where future attachments can occur. Our observations indicate that acoustics (and, in general, dynamic stress) can influence colloid-colloid and colloid-surface interactions in ways that could cause significant changes in porous-media permeability and mass transport. This would occur due to either buildup or release of colloids present in the porous matrix.

Osteoblast and osteoclast behaviors in the turnover of attachment bones during medaka tooth replacement.

PubMed

Mantoku, Akiko; Chatani, Masahiro; Aono, Kazushi; Inohaya, Keiji; Kudo, Akira

2016-01-15

Tooth replacement in polyphyodont is a well-organized system for maintenance of homeostasis of teeth, containing the dynamic structural change in skeletal tissues such as the attachment bone, which is the supporting element of teeth. Histological analyses have revealed the character of tooth replacement, however, the cellular mechanism of how skeletal tissues are modified during tooth replacement is largely unknown. Here, we showed the important role of osteoblasts for controlling osteoclasts to modify the attachment bone during tooth replacement in medaka pharyngeal teeth, coupled with an osterix-DsRed/TRAP-GFP transgenic line to visualize osteoblasts and osteoclasts. In the turnover of the row of attachment bones, these bones were resorbed at the posterior side where most developed functional teeth were located, and generated at the anterior side where teeth were newly erupted, which caused continuous tooth replacement. In the cellular analysis, osteoclasts and osteoblasts were located at attachment bones separately, since mature osteoclasts were localized at the resorbing side and osteoblasts gathered at the generating side. To demonstrate the role of osteoclasts in tooth replacement, we established medaka made deficient in c-fms-a by TALEN. c-fms-a deficient medaka showed hyperplasia of attachment bones along with reduced bone resorption accompanied by a low number of TRAP-positive osteoclasts, indicating an important role of osteoclasts in the turnover of attachment bones. Furthermore, nitroreductase-mediated osteoblast-specific ablation induced disappearance of osteoclasts, indicating that osteoblasts were essential for maintenance of osteoclasts for the proper turnover. Taken together, our results suggested that the medaka attachment bone provides the model to understand the cellular mechanism for tooth replacement, and that osteoblasts act in the coordination of bone morphology by supporting osteoclasts. Copyright © 2015 Elsevier Inc. All rights reserved.

Conformational dynamics of amyloid proteins at the aqueous interface

NASA Astrophysics Data System (ADS)

Armbruster, Matthew; Horst, Nathan; Aoki, Brendy; Malik, Saad; Soto, Patricia

2013-03-01

Amyloid proteins is a class of proteins that exhibit distinct monomeric and oligomeric conformational states hallmark of deleterious neurological diseases for which there are not yet cures. Our goal is to examine the extent of which the aqueous/membrane interface modulates the folding energy landscape of amyloid proteins. To this end, we probe the dynamic conformational ensemble of amyloids (monomer prion protein and Alzheimer's Ab protofilaments) interacting with model bilayers. We will present the results of our coarse grain molecular modeling study in terms of the existence of preferential binding spots of the amyloid to the bilayer and the response of the bilayer to the interaction with the amyloid. NSF Nebraska EPSCoR First Award

Structure and Dynamics of Water Confined in Imogolite Nanotubes.

PubMed

Scalfi, Laura; Fraux, Guillaume; Boutin, Anne; Coudert, François-Xavier

2018-06-12

We have studied the properties of water adsorbed inside nanotubes of hydrophilic imogolite, an aluminum silicate clay mineral, by means of molecular simulations. We used a classical force field to describe the water and the flexible imogolite nanotube and validated it against the data obtained from first-principles molecular dynamics. With it, we observe a strong structuration of the water confined in the nanotube, with specific adsorption sites and a distribution of hydrogen bond patterns. The combination of number of adsorption sites, their geometry, and the preferential tetrahedral hydrogen bonding pattern of water leads to frustration and disorder. We further characterize the dynamics of the water, as well as the hydrogen bonds formed between water molecules and the nanotube, which is found to be more than 1 order of magnitude longer than water-water hydrogen bonds.

Dynamical effects of stellar companions

NASA Astrophysics Data System (ADS)

Naoz, Smadar

2015-08-01

The fraction of stellar binaries in the field is extremely high (about 40% - 70% for > 1 Msun stars), and thus, given this frequency, a large fraction of all exoplanetary systems may reside in binaries. While close-in giant planets tend to be found preferentially in binary stellar systems it seems that the frequency of giant planets in close binaries (<100 AU) is significantly lower than in the overall population. Stellar companions’ gravitational perturbations may significantly alter the planetary orbits around their partner on secular timescales. They can drive planets to large eccentric orbits which can either result in plunging these planets into the star or shrinking their orbits and forming short period planets. I will review the dynamical effects stellar binaries have on a planetary systems. I will also present new results on the influence that stellar evolution has on the dynamical processes in these systems.

Charge Generation Dynamics in Efficient All-Polymer Solar Cells: Influence of Polymer Packing and Morphology.

PubMed

Gautam, Bhoj R; Lee, Changyeon; Younts, Robert; Lee, Wonho; Danilov, Evgeny; Kim, Bumjoon J; Gundogdu, Kenan

2015-12-23

All-polymer solar cells exhibit rapid progress in power conversion efficiency (PCE) from 2 to 7.7% over the past few years. While this improvement is primarily attributed to efficient charge transport and balanced mobility between the carriers, not much is known about the charge generation dynamics in these systems. Here we measured exciton relaxation and charge separation dynamics using ultrafast spectroscopy in polymer/polymer blends with different molecular packing and morphology. These measurements indicate that preferential face-on configuration with intermixed nanomorphology increases the charge generation efficiency. In fact, there is a direct quantitative correlation between the free charge population in the ultrafast time scales and the external quantum efficiency, suggesting not only the transport but also charge generation is key for the design of high performance all polymer solar cells.

Trees influence preferencial flow and water uptake in tropical savanna

NASA Astrophysics Data System (ADS)

Benegas, Laura; Bargues-Tobella, Aida; Hasselquist, Niles; Malmer, Anders; Ilstedt, Ulrik

2017-04-01

To address potential competition between trees and grasses for soil water, and to disentangle the main process responsible for local soil water dynamics in pasture ecosystems, we conducted a study of the soil water content and water source partitioning of grasses and trees within a pasture in the Copan River catchment, Honduras. We used differences in the 2H/1H (δD) isotopic signature of soil water (δSW) and the local meteoric water line (LMWL; δLMWL) as a relative index of evaporation, following a recent model proposed by Hasselquist et al (under review). The model uses Lc-excess calculated as the absolute value of the difference between measured δD and that predicted by the local meteoric water line (lc-excess = ¦δDM - δDP¦). Lc-excess values close to zero indicate little difference between soil water samples and local precipitation, whereas larger values indicate a greater degree of evaporation .()...(adapted from Landwehr and Coplen, 2006). From the relation between Lc-excess and SWC, we can tease apart different processes by which trees influence local soil water dynamics, where one such processes indicate that if preferential flow, i.e quick flows through macropores that by-pass the soil matrix, is the main pathway for water movement in the soil, then the Lc-excess values of soil water at deeper depths will be closer to zero than those of the surface soil, whereas relatively higher Lc-excess values would indicate increasing dominance of matrix flow. We found that soil underneath trees was wetter than underneath grasses at the dry season and we can relate this with a lack of clear relationship between Lc-excess and SWC and with the treés apparent shift to groundwater sources for root uptake especially in the dry season. Due to the positive correlation between Lc-excess and SWC under trees and due to the lower Lc-excess values found at subsoil below trees during the dry season, we can infer that preferential flow is also facilitated by the trees enhancing its contribution to groundwater recharge. The possible water losses via interception linked with trees on the soil water dynamic was counterbalanced by the positive contribution of trees to preferential flow and groundwater recharge.

An Application of System Dynamics Analysis to Ecosystem Management at the Poinsett Weapons Range, Shaw AFB SC

DTIC Science & Technology

1997-12-01

younger trees with thinner sapwood and greater heartwood diameter than other trees in the area . The RCW requires approximately 6 inches in diameter...and management areas and have explored applications of system dynamics modeling at the graduate level. The attached application addresses specific...Population Sensitivity to Birth Rate 62 10. RCW Population with Variation of Relatedness Entity 64 11. RCW Population with Variation of Foraging Area

The role of sexual expectancies of substance use as a mediator between adult attachment and drug use among gay and bisexual men.

PubMed

Starks, Tyrel J; Millar, Brett M; Tuck, Andrew N; Wells, Brooke E

2015-08-01

Research exploring substance use in gay and bisexual men has increasingly paid attention to interpersonal dynamics and relational concerns associated with the use of substances. The current study explored the role of adult attachment style on drug use as well as the potential mediating role of sexual expectancies of substance use among gay and bisexual men. Online survey data were gathered from 122 gay and bisexual men across the U.S., with a mean age of 33 years. All participants were HIV-negative and identified their relationship status as single. Survey measures included attachment style, sexual expectancies of substance use, and recent drug use. While neither anxious or avoidant attachment were directly associated with the odds of recent drug use, they were positively associated with sexual expectancies of substance use (β=0.27, p<0.01, and β=0.21, p<0.05) which, in turn, were positively associated with the odds of drug use (expB=1.09, p<0.01). Bootstrapping tests of indirect effects revealed a significant indirect relationship between anxious attachment and drug use through sexual expectancies of substance use (β=0.11, p<0.05), but not for avoidant attachment. This study highlights the importance of interpersonal expectancies as motivators for drug use among gay and bisexual men. Sexual expectancies of substance use were associated with drug use and anxious adult attachment was associated indirectly with drug use through these sexual expectancies. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Self-assembly of actin monomers into long filaments: Brownian dynamics simulations

NASA Astrophysics Data System (ADS)

Guo, Kunkun; Shillcock, Julian; Lipowsky, Reinhard

2009-07-01

Brownian dynamics simulations are used to study the dynamical process of self-assembly of actin monomers into long filaments containing up to 1000 actin protomers. In order to overcome the large separation of time scales between the diffusive motion of the free monomers and the relatively slow attachment and detachment processes at the two ends of the filaments, we introduce a novel rescaling procedure by which we speed all dynamical processes related to actin polymerization and depolymerization up by the same factor. In general, the actin protomers within a filament can attain three different states corresponding to a bound adenosine triphosphate (ATP), adenosine diphosphate with inorganic phosphate (ADP/P), and ADP molecule. The simplest situation that has been studied experimentally is provided by the polymerization of ADP-actin, for which all protomers are identical. This case is used to unravel certain relations between the filament's physical properties and the model parameters such as the attachment rate constant and the size of the capture zone, the detachment rate and the probability of the detached event, as well as the growth rate and waiting times between two successive attachment/detachment events. When a single filament is allowed to grow in a bath of constant concentration of free ADP-actin monomers, its growth rate increases linearly with the free monomer concentration in quantitative agreement with in vitro experiments. The results also show that the waiting time is governed by exponential distributions and that the two ends of a filament undergo biased random walks. The filament length fluctuations are described by a length diffusion constant that is found to attain a constant value at low ADP-actin concentration and to increase linearly with this concentration. It is straightforward to apply our simulation code to more complex processes such as polymerization of ATP-actin coupled to ATP hydrolysis, force generation by filaments, formation of filament bundles, and filament-membrane interactions.

Dismissing Attachment Characteristics Dynamically Modulate Brain Networks Subserving Social Aversion

PubMed Central

Krause, Anna Linda; Borchardt, Viola; Li, Meng; van Tol, Marie-José; Demenescu, Liliana Ramona; Strauss, Bernhard; Kirchmann, Helmut; Buchheim, Anna; Metzger, Coraline D.; Nolte, Tobias; Walter, Martin

2016-01-01

Attachment patterns influence actions, thoughts and feeling through a person’s “inner working model”. Speech charged with attachment-dependent content was proposed to modulate the activation of cognitive-emotional schemata in listeners. We performed a 7 Tesla rest-task-rest functional magnetic resonance imaging (fMRI)-experiment, presenting auditory narratives prototypical of dismissing attachment representations to investigate their effect on 23 healthy males. We then examined effects of participants’ attachment style and childhood trauma on brain state changes using seed-based functional connectivity (FC) analyses, and finally tested whether subjective differences in responsivity to narratives could be predicted by baseline network states. In comparison to a baseline state, we observed increased FC in a previously described “social aversion network” including dorsal anterior cingulated cortex (dACC) and left anterior middle temporal gyrus (aMTG) specifically after exposure to insecure-dismissing attachment narratives. Increased dACC-seeded FC within the social aversion network was positively related to the participants’ avoidant attachment style and presence of a history of childhood trauma. Anxious attachment style on the other hand was positively correlated with FC between the dACC and a region outside of the “social aversion network”, namely the dorsolateral prefrontal cortex, which suggests decreased network segregation as a function of anxious attachment. Finally, the extent of subjective experience of friendliness towards the dismissing narrative was predicted by low baseline FC-values between hippocampus and inferior parietal lobule (IPL). Taken together, our study demonstrates an activation of networks related to social aversion in terms of increased connectivity after listening to insecure-dismissing attachment narratives. A causal interrelation of brain state changes and subsequent changes in social reactivity was further supported by our observation of direct prediction of neuronal responses by individual attachment and trauma characteristics and reversely prediction of subjective experience by intrinsic functional connections. We consider these findings of activation of within-network and between-network connectivity modulated by inter-individual differences as substantial for the understanding of interpersonal processes, particularly in clinical settings. PMID:27014016

Unresolved attachment and agency in women victims of intimate partner violence: A case-control study.

PubMed

Pallini, Susanna; Alfani, Agnese; Marech, Lucrezia; Laghi, Fiorenzo

2017-06-01

Women victims of IPV are more likely insecurely attached and have experienced childhood abuse, which according to the attachment theory is deeply related to disorganized attachment. This case-control study was performed with the aim to compare the attachment status and the defensive processing patterns of women victims of IPV (cases) with women with no experiences of IPV (controls). Cases were 16 women with an age range from 26 years to 51 years. The control group included 16 women with an age range from 26 years to 59 years. Women's states of mind in regard to attachment were evaluated with the Adult Attachment Projective Picture System, which allows classifying attachment status and defensive mechanisms. Compared with control group, most IPV women resulted having an unresolved attachment status and describing characters less capable to draw upon internal resources, that is, internalized secure base, and less capable to act than controls. Women victims of IPV used significantly more words referring danger and failed protection than controls. The results evidenced the strong effectiveness of the AAP on analysing the psychological attitudes of women victims of IPV. The dramatic events lived by the women victims of IPV are so dominant in their minds that they invade their stories. This could represent a clue of emotional dysregulation. The use of AAP improves the understanding of the agency of self and of the specific levels of trauma experienced by IPV victims, on clarifying their frightening/frightened dynamic, typical of the disorganized attachment relationship, which undermines their activity of mentalization. The therapist will assume the stance of a secure base and then both promoting exploration and contrasting impotence, humiliation, and subordination that IPV women have experienced. This therapeutic interpersonal context will be functional to reach two different but related therapeutic goals: (1) to facilitate the rebuilding of agency (through an activation of subject to explore concrete strategies for exiting from IPV), (2) to explore attachment-related segregated systems from awareness, and to integrate them in memory. © 2016 The British Psychological Society.

Early formation of preferential flow in a homogeneous snowpack observed by micro-CT

NASA Astrophysics Data System (ADS)

Avanzi, Francesco; Petrucci, Giacomo; Matzl, Margret; Schneebeli, Martin; De Michele, Carlo

2017-05-01

We performed X-ray microtomographic observations of wet-snow metamorphism during controlled continuous melting and melt-freeze events in the laboratory. Three blocks of snow were sieved into boxes and subjected to cyclic, superficial heating or heating-cooling to reproduce vertical water infiltration patterns in snow similarly to natural conditions. Periodically, samples were taken at different heights and scanned. Results suggest that wet-snow metamorphism dynamics are highly heterogeneous even in an initially homogeneous snowpack. Consistent with previous work, we observed an increase with time in the thickness of the ice structure, which is a measure of grain size. However, this was coupled with large temporal scatter between consecutive measurements of the specific surface area and of the statistical moments of grain thickness distributions. Because of marked differences in the right tail, grain thickness distributions did not show shape invariance with time, contrary to previous analyses. In our experiments, wet-snow metamorphism showed two strikingly different patterns: homogeneous coarsening superimposed by faster heterogeneous coarsening in areas that were affected by preferential percolation of water. Liquid water movement in snow and fast structural evolution may be thus intrinsically coupled by early formation of preferential flow at local scale. These observations suggest that further experiments are highly needed to fully understand wet-snow metamorphism and infiltration patterns in a natural snowpack.