Experimental verification of democratic particle motions by direct imaging of glassy colloidal systems

We analyze data from confocal microscopy experiments of a colloidal suspension to validate predictions of rapid sporadic events responsible for structural relaxation in a glassy sample. The trajectories of several thousand colloidal particles are analyzed, confirming the existence of rapid sporadic events responsible for the structural relaxation of significant regions of the sample, and complementing prior observations of dynamical heterogeneity. The emergence of relatively compact clusters of mobility allows the dynamics to transition between the large periods of local confinement within its potential energy surface, in good agreement with the picture envisioned long ago by Adam and Gibbs and Goldstein.Comment: 4 pages, 5 figure

Metabasin dynamics and local structure in supercooled water

We employ the Distance Matrix method to investigate metabasin dynamics in supercooled water. We find that the motion of the system consists in the exploration of a finite region of configuration space (enclosing several distinct local minima), named metabasin, followed by a sharp crossing to a different metabasin. The characteristic time between metabasin transitions is comparable to the structural relaxation time, suggesting that these transitions are relevant for the long time dynamics. The crossing between metabasins is accompanied by very rapid diffusional jumps of several groups of dynamically correlated particles. These particles form relatively compact clusters and act as cooperative relaxing units responsible for the density relaxation. We find that these mobile particles are often characterized by an average coordination larger than four, i.e. are located in regions where the tetrahedral hydrogen bond network is distorted

Relaxation pathway confinement in glassy dynamics

We compute for an archetypical glass-forming system the excess of particle mobility distributions over the corresponding distribution of dynamic propensity, a quantity that measures the tendency of the particles to be mobile and reflects the local structural constraints. This enables us to demonstrate that, on supercooling, the dynamical trajectory in search for a relaxation event must deal with an increasing confinement of relaxation pathways. This "entropic funnel" of relaxation pathways built upon a restricted set of mobile particles is also made evident from the decay and further collapse of the associated Shannon entropy.Fil: Rodriguez Fris, Jorge Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur; ArgentinaFil: Appignanesi, Gustavo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur; ArgentinaFil: Frechero, Marisa Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur; Argentin

Hydrophobicity and geometry: Water at curved graphitic-likesurfaces and within model pores in self-assembled monolayers

In this work we perform molecular dynamics simulations of water in contact with simple modelhydrophobic surfaces and pores in order to test the role of local geometry on hydrophobicity. Specif-ically, we study different quantities like orientational ordering, density fluctuations and water residencetimes (autocorrelation functions) around graphene sheets, at the exterior of single-walled carbon nano-tubes, at alkane-like self-assembled monolayers (SAMs) and at pores of different sizes carved in suchSAMs. We show that in the case of the convex graphitic-like surfaces, the cuvature does not affect thelocal hydrophobicity. However, significant curvature dependence will be made evident for the concavesurfaces of the pores carved in the SAMs. The geometrically induced dehydration that occurs as the poresize reaches the subnanometric regime might be operative in realistic settings like protein binding siteswhich require water remotion upon ligand binding.Fil: Alarcon, Laureano Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur; ArgentinaFil: Montes de Oca Avalos, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur; ArgentinaFil: Accordino, Sebastian Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur; ArgentinaFil: Rodriguez Fris, Jorge Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur; ArgentinaFil: Appignanesi, Gustavo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur; Argentin

Fathers, Mothers, Marriages, and Children: Toward a Contextual Model of Positive Paternal Influence

This research explored positive paternal involvement in the lives of children within the broader familial context of marital dynamics and positive maternal involvement. The National Survey of Families and Households (NSFH) was used to obtain a longitudinal subsample of 582 first-married couples, as well as the wide range of variables necessary to explore this broader context of paternal influence. Three research questions guided the study: (I) What is the unique contribution of positive paternal involvement-with respect to positive maternal involvement and marital quality- in child ren\u27s development? (2) How does the influence of positive paternal involvement interact with the influence of positive maternal involvement and marital quality to influence children \u27s development? (3) To what degree do fathers indirectly influence their children via the marital relationship and the mother-child relationship? Analysis demonstrated little evidence of fathers \u27 unique contribution to children \u27s aggressive/anti social behavior, school problems, and other outcomes. Similarly, analysis demonstrated no indirect effects for paternal involvement across the 4-5 years span between Wave I and Wave 2 of the NSFH. Specifically, fathers\u27 involvement did not indirectly affect children \u27s outcomes via either the marital relationship or maternal involvement. However, limitations relating to internal reliability rendered findings questionable. Analysis also demonstrated a limited pattern of interaction effects between paternal involvement measures and marital and maternal variables. Specifically, Wave 2 paternal positive activities demonstrated meaningful interactions with maternal positive activities, marital happiness, and marital conflict, with respect to their influence on children\u27s aggressive/anti social behavior interaction between paternal positive activities and marital variables indicated that paternal involvement is capable of interacting with other aspects of family context in ways which have both positive and negative consequences for children. Future research efforts addressing these questions should assess parental involvement in greater depth and breath, incorporating a framework capable of addressing both parental warmth and control. Similarly, future research should consider methods capable of addressing multicolinearity resulting from parallel paternal and maternal variables. Finally, future research should explore the various ways in which paternal involvement interacts with other sources of influence within families to impact the lives of children

The Root Hair Specific SYP123 Regulates the Localization of Cell Wall Components and Contributes to Rizhobacterial Priming of Induced Systemic Resistance

Indexación: Web of Science.Root hairs are important for nutrient and water uptake and are also critically involved the interaction with soil inhabiting microbiota. Root hairs are tubular-shaped outgrowths that emerge from trichoblasts. This polarized elongation is maintained and regulated by a robust mechanism involving the endomembrane secretory and endocytic system. Members of the syntaxin family of SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) in plants (SYP), have been implicated in regulation of the fusion of vesicles with the target membranes in both exocytic and endocytic pathways. One member of this family. SYP123, is expressed specifically in the root hairs and accumulated in the growing tip region. This study shows evidence of the SYP123 role in polarized trafficking using knockout insertional mutant plants. We were able to observe defects in the deposition of cell wall proline rich protein PRP3 and cell wall polysaccharides. In a complementary strategy, similar results were obtained using a plant expressing a dominant negative soluble version of SYP123 (SP2 fragment) lacking the transmembrane domain. The evidence presented indicates that SYP123 is also regulating PRP3 protein distribution by recycling by endocytosis. We also present evidence that indicates that SYP123 is necessary for the response of roots to plant growth promoting rhizobacterium (PGPR) in order to trigger trigger induced systemic response (ISR). Plants with a defective SYP123 function were unable to mount a systemic acquired resistance in response to bacterial pathogen infection and ISR upon interaction with rhizobacteria. These results indicated that SYP123 was involved in the polarized localization of protein and polysaccharides in growing root hairs and that this activity also contributed to the establishment of effective plant defense responses. Root hairs represent very plastic structures were many biotic and abiotic factors can affect the number, anatomy and physiology of root hairs. Here, we presented evidence that indicates that interactions with soil PGPR could be closely regulated by signaling involving secretory and/or endocytic trafficking at the root hair tip as a quick way to response to changing environmental conditions.http://journal.frontiersin.org/article/10.3389/fpls.2016.01081/ful

Global optimisation of large-scale quadratic programs: application to short-term planning of industrial refinery-petrochemical complexes

This thesis is driven by an industrial problem arising in the short-term planning of an integrated refinery-petrochemical complex (IRPC) in Colombia. The IRPC of interest is composed of 60 industrial plants and a tank farm for crude mixing and fuel blending consisting of 30 additional units. It considers both domestic and imported crude oil supply, as well as refined product imports such as low sulphur diesel and alkylate. This gives rise to a large-scale mixed-integer quadratically constrained quadratic program (MIQCQP) comprising about 7,000 equality constraints with over 35,000 bilinear terms and 280 binary variables describing operating modes for the process units. Four realistic planning scenarios are recreated to study the performance of the algorithms developed through the thesis and compare them to commercial solvers. Local solvers such as SBB and DICOPT cannot reliably solve such large-scale MIQCQPs. Usually, it is challenging to even reach a feasible solution with these solvers, and a heuristic procedure is required to initialize the search. On the other hand, global solvers such as ANTIGONE and BARON determine a feasible solution for all the scenarios analysed, but they are unable to close the relaxation gap to less than 40% on average after 10h of CPU runtime. Overall, this industrial-size problem is thus intractable to global optimality in a monolithic way. The first main contribution of the thesis is a deterministic global optimisation algorithm based on cluster decomposition (CL) that divides the network into groups of process units according to their functionality. The algorithm runs through the sequences of clusters and proceeds by alternating between: (i) the (global) solution of a mixed-integer linear program (MILP), obtained by relaxing the bilinear terms based on their piecewise McCormick envelopes and a dynamic partition of their variable ranges, in order to determine an upper bound on the maximal profit; and (ii) the local solution of a quadratically-constrained quadratic program (QCQP), after fixing the binary variables and initializing the continuous variables to the relaxed MILP solution point, in order to determine a feasible solution (lower bound on the maximal profit). Applied to the base case scenario, the CL approach reaches a best solution of 2.964 MMUSD/day and a relaxation gap of 7.5%, a remarkable result for such challenging MIQCQP problem. The CL approach also vastly outperforms both ANTIGONE (2.634 MMUSD/day, 32% optimality gap) and BARON (2.687 MMUSD/day, 40% optimality gap). The second main contribution is a spatial Lagrangean decomposition, which entails decomposing the IRPC short-term planning problem into a collection of smaller subproblems that can be solved independently to determine an upper bound on the maximal profit. One advantage of this strategy is that each sub-problem can be solved to global optimality, potentially providing good initial points for the monolithic problem itself. It furthermore creates a virtual market for trading crude blends and intermediate refined–petrochemical streams and seeks an optimal trade-off in such a market, with the Lagrange multipliers acting as transfer prices. A decomposition over two to four is considered, which matches the crude management, refinery, petrochemical operations, and fuel blending sections of the IRPC. An optimality gap below 4% is achieved in all four scenarios considered, which is a significant improvement over the cluster decomposition algorithm.Open Acces

Shedding My Hair: Reflections on a Cross Generational Theater Experience

For my Columbia MFA Directing Thesis Project I decided to direct a production of Hair: The American Tribal Love-Rock Musical. This document constitutes a small record of all the work that went into developing the concept and actually creating this thesis production, which premiered in New York City at the Connelly Theater on March 29th 2017, and ran for five performances. One of the most universal aspects of a theater event is its ephemerality, it pops into and out of existence very quickly and leaves a trail of effects in it's wake. In my opinion theater is uselessly judged with conventional categories like beauty, entertainment value, even intention or clarity. Theater can only ever be measured by the force and form of it's collision with our society, and by the magnitude of the ripples that this impact leaves behind