The Industrial Research Program at the European Synchrotron Radiation Facility: The Past,the Present,and Challenges for the Future

The challenge of harnessing the power of third-generation synchrotron sources for industrial R&D has been taken up by the ESRF ever since the first users arrived in 1994. However, working with industry has its own special requirements, and often mismatches and clashes between a traditional scientific “ivory tower” culture and the needs of the market-driven commercial world. After more than 15 years of industrial research at the ESRF, during which strong industrial programs in protein crystallography and microtomography have been established, we continue to build bridges between the two worlds.     

Integrating restoration and scheduling decisions for disrupted interdependent infrastructure systems

We consider the problem faced by managers of critical civil interdependent infrastructure systems of restoring essential public services after a non-routine event causes disruptions to these services. In order to restore the services, we must determine the set of components (or tasks) that will be temporarily installed or repaired, assign these tasks to work groups, and then determine the schedule of each work group to complete the tasks assigned to it. These restoration planning and scheduling decisions are often undertaken in an independent, sequential manner. We provide mathematical models and optimization algorithms that integrate the restoration and planning decisions and specifically account for the interdependencies between the infrastructure systems. The objective function of this problem provides a measure of how well the services are being restored over the horizon of the restoration plan, rather than just focusing on the performance of the systems after all restoration efforts are complete. We test our methods on realistic data representing infrastructure systems in New York City. Our computational results demonstrate that we can provide integrated restoration and scheduling plans of high quality with limited computational resources. We also discuss the benefits of integrating the restoration and scheduling decisions.     

Parametric Estimation of a Boolean Segment Process with Stochastic Restoration Estimation

Abstract

We propose a stochastic restoration estimation (SRE) algorithm to estimate the parameters of the length distribution of a boolean segment process. A boolean segment process is a stochastic process obtained by considering the union of independent random segments attached to random points independently scattered on the plane. Each iteration of the SRE algorithm has two steps: first, censored segments are restored; second, based on these restored data, parameter estimations are updated. With a usually straightforward implementation, this algorithm is particularly interesting when censoring effects are difficult to take into account. We illustrate this method in two situations where the parameter of interest is either the mean of the segment length distribution or the variance of its logarithm. Its application to vine shoot length distribution estimation is presented.     

Defining rules for the shape evolution of gold nanoparticles

The roles of silver ions and halides (chloride, bromide, and iodide) in the seed-mediated synthesis of gold nanostructures have been investigated, and their influence on the growth of 10 classes of nanoparticles that differ in shape has been determined. We systematically studied the effects that each chemical component has on the particle shape, on the rate of particle formation, and on the chemical composition of the particle surface. We demonstrate that halides can be used to (1) adjust the reduction potential of the gold ion species in solution and (2) passivate the gold nanoparticle surface, both of which control the reaction kinetics and thus enable the selective synthesis of a series of different particle shapes. We also show that silver ions can be used as an underpotential deposition agent to access a different set of particle shapes by controlling growth of the resulting gold nanoparticles through surface passivation (more so than kinetic effects). Importantly, we show that the density of silver coverage can be controlled by the amount and type of halide present in solution. This behavior arises from the decreasing stability of the underpotentially deposited silver layer in the presence of larger halides due to the relative strengths of the Ag(+)/Ag(0)-halide and Au(+)/Au(0)-halide interactions, as well as the passivation effects of the halides on the gold particle surface. We summarize this work by proposing a set of design considerations for controlling the growth and final shape of gold nanoparticles prepared by seed-mediated syntheses through the judicious use of halides and silver ions.     

Spherical nucleic acids

A historical perspective of the development of spherical nucleic acid (SNA) conjugates and other three-dimensional nucleic acid nanostructures is provided. This Perspective details the synthetic methods for preparing them, followed by a discussion of their unique properties and theoretical and experimental models for understanding them. Important examples of technological advances made possible by their fundamental properties spanning the fields of chemistry, molecular diagnostics, gene regulation, medicine, and materials science are also presented.     

Structural intermediates during α-synuclein fibrillogenesis on phospholipid vesicles

α-Synuclein (AS) fibrils are the main protein component of Lewy bodies, the pathological hallmark of Parkinson's disease and other related disorders. AS forms helices that bind phospholipid membranes with high affinity, but no atomic level data for AS aggregation in the presence of lipids is yet available. Here, we present direct evidence of a conversion from α-helical conformation to β-sheet fibrils in the presence of anionic phospholipid vesicles and direct conversion to β-sheet fibrils in their absence. We have trapped intermediate states throughout the fibril formation pathways to examine the structural changes using solid-state NMR spectroscopy and electron microscopy. The comparison between mature AS fibrils formed in aqueous buffer and those derived in the presence of anionic phospholipids demonstrates no major changes in the overall fibril fold. However, a site-specific comparison of these fibrillar states demonstrates major perturbations in the N-terminal domain with a partial disruption of the long β-strand located in the 40s and small perturbations in residues located in the "non-β amyloid component" (NAC) domain. Combining all these results, we propose a model for AS fibrillogenesis in the presence of phospholipid vesicles.     

Synthetic principles directing charge transport in low-band-gap dithienosilole-benzothiadiazole copolymers

Given the fundamental differences in carrier generation and device operation in organic thin-film transistors (OTFTs) and organic photovoltaic (OPV) devices, the material design principles to apply may be expected to differ. In this respect, designing organic semiconductors that perform effectively in multiple device configurations remains a challenge. Following "donor-acceptor" principles, we designed and synthesized an analogous series of solution-processable π-conjugated polymers that combine the electron-rich dithienosilole (DTS) moiety, unsubstituted thiophene spacers, and the electron-deficient core 2,1,3-benzothiadiazole (BTD). Insights into backbone geometry and wave function delocalization as a function of molecular structure are provided by density functional theory (DFT) calculations at the B3LYP/6-31G(d,p) level. Using a combination of X-ray techniques (2D-WAXS and XRD) supported by solid-state NMR (SS-NMR) and atomic force microscopy (AFM), we demonstrate fundamental correlations between the polymer repeat-unit structure, molecular weight distribution, nature of the solubilizing side-chains appended to the backbones, and extent of structural order attainable in p-channel OTFTs. In particular, it is shown that the degree of microstructural order achievable in the self-assembled organic semiconductors increases largely with (i) increasing molecular weight and (ii) appropriate solubilizing-group substitution. The corresponding field-effect hole mobilities are enhanced by several orders of magnitude, reaching up to 0.1 cm(2) V(-1) s(-1) with the highest molecular weight fraction of the branched alkyl-substituted polymer derivative in this series. This trend is reflected in conventional bulk-heterojunction OPV devices using PC(71)BM, whereby the active layers exhibit space-charge-limited (SCL) hole mobilities approaching 10(-3) cm(2) V(-1) s(-1), and yield improved power conversion efficiencies on the order of 4.6% under AM1.5G solar illumination. Beyond structure-performance correlations, we observe a large dependence of the ionization potentials of the polymers estimated by electrochemical methods on polymer packing, and expect that these empirical results may have important consequences on future material study and device applications.     

Laboratory investigation of a passive acoustic method for measurement of underwater gas seep ebullition

Passive acoustic techniques are of interest as a low-power means of quantifying underwater point-source gas ebullition. Toward the development of systems for logging natural seep activity, laboratory experiments were performed that exploited the bubble's Minnaert natural frequency for the measurement of gas flow from a model seep. Results show agreement among acoustic, optical, and gas trap ebullition measurements over the range of emission rates from 0 to 10 bubbles per second. A mathematical model is proposed to account for the real gas behavior of bubbles which cannot be approximated as ideal, such as methane at marine depths exceeding 30 m.     

Ultranarrow Faraday rotation filter at the Rb D1 line

We present a theoretical and experimental study of the ultranarrow bandwidth Faraday anomalous dispersion optical filter operating at the rubidium D1 line (795 nm). This atomic line gives better performance than other lines for key figures of merit, e.g., simultaneously 71% transmission, 445 MHz bandwidth, and 1.2 GHz equivalent-noise bandwidth.     

Constructing Graphical Representations: Middle Schoolers' Intuitions and Developing Knowledge About Slope and Y‐intercept

Middle‐school students are expected to understand key components of graphs, such as slope and y‐intercept. However, constructing graphs is a skill that has received relatively little research attention. This study examined students' construction of graphs of linear functions, focusing specifically on the relative difficulties of graphing slope and y‐intercept. Sixth‐graders' responses prior to formal instruction in graphing reveal their intuitions about slope and y‐intercept, and seventh‐ and eighth‐graders' performance indicates how instruction shapes understanding. Students' performance in graphing slope and y‐intercept from verbally presented linear functions was assessed both for graphs with quantitative features and graphs with qualitative features. Students had more difficulty graphing y‐intercept than slope, particularly in graphs with qualitative features. Errors also differed between contexts. The findings suggest that it would be valuable for additional instructional time to be devoted to y‐intercept and to qualitative contexts.