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Multi-electron Reduction Capacity and Multiple Binding Pockets in Metal-Organic Redox Assembly at Surfaces
No full textMetal–ligand complexation at surfaces utilizing redox‐active ligands has been demonstrated to produce uniform single‐site metals centers in regular coordination networks. Two key design considerations are the electron storage capacity of the ligand and the metal‐coordinating pockets on the ligand. In an effort to move toward greater complexity in the systems, particularly dinuclear metal centers, we designed and synthesized tetraethyltetra‐aza‐anthraquinone, TAAQ, which has superior electron storage capabilities and four ligating pockets in a diverging geometry. Cyclic voltammetry studies of the free ligand demonstrate its ability to undergo up to a four‐electron reduction. Solution‐based studies with an analogous ligand, diethyldi‐aza‐anthraquinone, demonstrate these redox capabilities in a molecular environment. Surface studies conducted on the Au(111) surface demonstrate TAAQ′s ability to complex with Fe. This complexation can be observed at different stoichiometric ratios of Fe:TAAQ as Fe 2p core level shifts in X‐ray photoelectron spectroscopy. Scanning tunneling microscopy experiments confirmed the formation of metal–organic coordination structures. The striking feature of these structures is their irregularity, which indicates the presence of multiple local binding motifs. Density functional theory calculations confirm several energetically accessible Fe:TAAQ isomers, which accounts for the non‐uniformity of the chains
The Symmetrical Wave Pattern of Base-Pair Substitution Rates across the Escherichia coli Chromosome Has Multiple Causes
No full textMutation accumulation experiments followed by whole-genome sequencing have revealed that, for several bacterial species, the rate of base-pair substitutions (BPSs) is not constant across the chromosome but varies in a wave-like pattern that is symmetrical about the origin of replication. The experiments reported here demonstrated that, in Escherichia coli, several interacting factors determine the wave. The origin is a major driver of BPS rates. When it is relocated, the BPS rates in a 1,000-kb region surrounding the new origin reproduce the pattern that surrounds the normal origin. However, the pattern across distant regions of the chromosome is unaltered and thus must be determined by other factors. Increasing the deoxynucleoside triphosphate (dNTP) concentration shifts the wave pattern away from the origin, supporting the hypothesis that fluctuations in dNTP pools coincident with replication firing contribute to the variations in the mutation rate. The nucleoid binding proteins (HU and Fis) and the terminus organizing protein (MatP) are also major factors. These proteins alter the three-dimensional structure of the DNA, and results suggest that mutation rates increase when highly structured DNA is replicated. Biases in error correction by proofreading and mismatch repair, both of which may be responsive to dNTP concentrations and DNA structure, also are major determinants of the wave pattern. These factors should apply to most bacterial and, possibly, eukaryotic genomes and suggest that different areas of the genome evolve at different rates
Uniqueness and Regularity for the Navier--Stokes--Cahn--Hilliard System
No full textThe motion of two contiguous incompressible and viscous fluids is described within the diffuse interface theory by the so-called Model H. The system consists of the Navier--Stokes equations, which are coupled with the Cahn--Hilliard equation associated to the Ginzburg--Landau free energy with physically relevant logarithmic potential. This model is studied in bounded smooth domains in , , and and is supplemented with a no-slip condition for the velocity, homogeneous Neumann boundary conditions for the order parameter and the chemical potential, and suitable initial conditions. We study uniqueness and regularity of weak and strong solutions. In a two-dimensional domain, we show the uniqueness of weak solutions and the existence and uniqueness of global strong solutions originating from an initial velocity , namely, such that . In addition, we prove further regularity properties and the validity of the instantaneous separation property. In a three-dimensional domain we show the existence and uniqueness of local strong solutions with initial velocity . Read More: https://epubs.siam.org/doi/10.1137/18M122345
Measurement of the longitudinal spin asymmetries for weak boson production in proton-proton collisions at =510 GeV
No full textWe report new STAR measurements of the single-spin asymmetries for and bosons produced in polarized proton--proton collisions at = 510 GeV as a function of the decay-positron and decay-electron pseudorapidity. The data were obtained in 2013 and correspond to an integrated luminosity of 250 pb. The results are combined with previous results obtained with 86 pb. A comparison with theoretical expectations based on polarized lepton-nucleon deep-inelastic scattering and prior polarized proton--proton data suggests a difference between the and quark helicity distributions for . In addition, we report new results for the double-spin asymmetries for , as well as for production and subsequent decay into electron--positron pairs
Deep Underground Neutrino Experiment (DUNE), Far Detector Technical Design Report, Volume III: DUNE Far Detector Technical Coordination
No full textThe preponderance of matter over antimatter in the early universe, the dynamics of the supernovae that produced the heavy elements necessary for life, and whether protons eventually decay -- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our universe, its current state, and its eventual fate. The Deep Underground Neutrino Experiment (DUNE) is an international world-class experiment dedicated to addressing these questions as it searches for leptonic charge-parity symmetry violation, stands ready to capture supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector technical design report (TDR) describes the DUNE physics program and the technical designs of the single- and dual-phase DUNE liquid argon TPC far detector modules. Volume III of this TDR describes how the activities required to design, construct, fabricate, install, and commission the DUNE far detector modules are organized and managed. This volume details the organizational structures that will carry out and/or oversee the planned far detector activities safely, successfully, on time, and on budget. It presents overviews of the facilities, supporting infrastructure, and detectors for context, and it outlines the project-related functions and methodologies used by the DUNE technical coordination organization, focusing on the areas of integration engineering, technical reviews, quality assurance and control, and safety oversight. Because of its more advanced stage of development, functional examples presented in this volume focus primarily on the single-phase (SP) detector module
COVID-19 demonstrates the value of open access: What happens next?
No full textIn the wake of COVID-19, many publishers have tacitly agreed that open access is beneficial to scientific advancement and necessary to move science forward to combat disease. Publishers have committed to open access publication of scientific articles relating to the disease. Some are facilitating rapid and open peer review and fast-tracking the publishing of related research. Pulitzer Prize-winning journalist Michael Hiltzig refers to this convincing demonstration of the value of open access to scientific research as one of the most important positive disruptions caused by COVID-19
Development of Third Graders' Identities as "Persons Who Understand Nature of Science" Through a Gravity Unit
Get PDFNature of science (NOS) is a critical component and should be part of all science lessons. It is critical to begin NOS instruction in the elementary grades, to help young children develop an identity as persons who can conceptualize NOS ideas. The purpose of this study was to explore third grade elementary students’ Nature of Science (NOS) identities as a result of participating in a unit on gravity. The research question specifically was “How do third graders’ NOS identities change as a result of participating in a unit on gravity?” Explicit reflective NOS instruction was embedded in a unit on gravity. Data included videotapes of the lessons including class discussions prior to and after the lesson, and use of children’s literature. Other data included copies of student work and student science notebooks, and their presentations of work. Data were analyzed independently by three researchers for comparison of analysis. NOS identity development was found to be related to ideas that were “connections to real life,” “class discussions of ideas,” and “making connections to other science content.” Students in this class were able to use and apply NOS terms accurately. Results support that elementary students can learn NOS through appropriate instruction
New Research on Developmental Idealism
Get PDFIn this introduction, we offer an overview of developmental idealism (DI) theory and the contributions of this special issue. DI is a collection of values and beliefs about socioeconomic development and its causal links to other elements of societies. Within DI, some societal elements are identified as “modern,” inherently good, and helpful to development, while others are identified as “traditional,” undesirable, and unhelpful to development. DI theory posits that these schemas spread from Northwest European elites to ordinary people. In turn, people are motivated to adopt “modern” behaviors because they are seen as the means of achieving a good life and socioeconomic development. The articles in this special issue contribute to the empirical investigation of DI theory in a variety of ways. This issue enriches the DI methodological toolkit, demonstrating, for example, that DI measures are valid and reliable and that internet search queries can be used to examine DI. The articles also make strides in assessing the prevalence and nature of DI thinking, from the internet to far-flung geographic locations, including Albania, Kenya, Nepal, and Vietnam. Finally, this issue contributes to identifying pathways for the spread of DI, pointing to national elites, monetary incentives, and television
Examining the effectiveness of measuring team brand association networks with textual analysis software
Get PDFAs brand associations are a key component of team brand equity, and ultimately influence consumer behaviour, it is important to have accurate measures of these associations. Previous research has developed scales to measure team brand associations, yet it has been suggested that pre-existing scales may not capture salient features of brands and any unique brand associations not captured by scaled measures. In addition, scales will not uncover the brand association networks and how team brand associations are interconnected. However, with advances in technology there is potential to develop methods which accomplish these goals. This study utilises a freethought listing technique to capture team brand associations which were then analysed by the Leximancer textual analysis software. The results suggest that this method provides an avenue to more accurately uncover the most salient team brand associations and to visualise team brand association networks
Sticker and Emoji Use in Facebook Messenger: Implications for Graphicon Change
Get PDFThis study posits that graphicon use follows an evolutionary trajectory characterized by stages. Drawing on evidence that the uses and functions of emoticons have changed over time and that the introduction of emoji affected the popularity and usage of emoticons, we examine the uses of the newer types, emoji and stickers, and consider the relationship of stickers to emoji. Adapting the apparent-time method from the sociolinguistic study of language change, we compare sticker and emoji use by English-speaking Facebook Messenger users, exploring how they are used and under what conditions using semi-structured interviews and a large-scale survey. Stickers are argued to be more pragmatically marked for emotional intensity, positivity, and intimacy, characteristic of a more recent stage of evolution, while emoji use exhibits signs of conventionalization and pragmatic unmarking. The identification of patterns that characterize evolutionary stages has implications for future graphicon use