Peptide-directed crystal growth modification in the formation of ZnO

Biomolecule-mediated synthesis is fascinating in terms of the level of control and the intricate hierarchical structures of the materials that can be produced. In this study we compare the behavior of a phage display identified peptide, EAHVMHKVAPRP (EM-12) with that of a mutant peptide EAHVCHKVAPRP (EC-12), having additional complexation capability, on the formation of ZnO from solution. The synthesis conditions (Zn(CH3COO)2–NH3 hydrothermal method at 50 °C) were chosen to generate rod-shaped ZnO via layered basic zinc salts (LBZs) as intermediates. Both peptides affected the crystal formation process by moderating the amount of Zn2+ ions in solution (EC12 having a greater effect than EM12) but only EC12 was shown to interact with the solid phase(s) formed during the reaction. Depending on the peptide concentration used, EM-12 was shown to delay and/or suppress ZnO formation. In contrast, additions of EC-12, although leading to the retention of higher levels of Zn2+ ions in solution did not similarly delay the transformation of the intermediate phases to ZnO but were found to dramatically modify the morphology of ZnO crystallites with mushroom shaped crystals being formed. From the results of detailed materials characterization and changes in the morphology observed, the interactions between the peptide(s) and solution and solid state species present during the process of ZnO crystal formation in the presence of EM-12 and EC-12 are proposed

Direct observation of delithiation as the origin of analog memristance in LixNbO2

The discovery of analog LixNbO2 memristors revealed a promising new memristive mechanism wherein the diffusion of Li+ rather than O2- ions enables precise control of the resistive states. However, directly correlating lithium concentration with changes to the electronic structure in active layers remains a challenge and is required to truly understand the underlying physics. Chemically delithiated single crystals of LiNbO2 present a model system for correlating lithium variation with spectroscopic signatures from operando soft x-ray spectroscopy studies of device active layers. Using electronic structure modeling of the x-ray spectroscopy of LixNbO2 single crystals, we demonstrate that the intrinsic memristive behavior in LixNbO2 active layers results from field-induced degenerate p-type doping. We show that electrical operation of LixNbO2-based memristors is viable even at marginal Li deficiency and that the analog memristive switching occurs well before the system is fully metallic. This study serves as a benchmark for material synthesis and characterization of future LixNbO2-based memristor devices and suggests that valence change switching is a scalable alternative that circumvents the electroforming typically required for filamentary-based memristors

A survey on health-promoting lifestyle among community-dwelling older people with hypertension in Macau

2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Early Ultraviolet Observations of Type IIn Supernovae Constrain the Asphericity of Their Circumstellar Material

© 2020. The American Astronomical Society. All rights reserved.. We present a survey of the early evolution of 12 Type IIn supernovae (SNe IIn) at ultraviolet and visible light wavelengths. We use this survey to constrain the geometry of the circumstellar material (CSM) surrounding SN IIn explosions, which may shed light on their progenitor diversity. In order to distinguish between aspherical and spherical CSM, we estimate the blackbody radius temporal evolution of the SNe IIn of our sample, following the method introduced by Soumagnac et al. We find that higher-luminosity objects tend to show evidence for aspherical CSM. Depending on whether this correlation is due to physical reasons or to some selection bias, we derive a lower limit between 35% and 66% for the fraction of SNe IIn showing evidence for aspherical CSM. This result suggests that asphericity of the CSM surrounding SNe IIn is common - consistent with data from resolved images of stars undergoing considerable mass loss. It should be taken into account for more realistic modeling of these events

Understanding the impact of diet and nutrition on symptoms of Tourette Syndrome: A Scoping Review

This document is the accepted manuscript version. The final, definitive version of this paper has been published in Journal of Child Health Care, December 2017, published by SAGE Publishing, doi:https://doi.org/10.1177/1367493517748373.Anecdotal reports frequently suggest some dietary involvement in the maintenance of tics in children with Tourette syndrome (TS). This scoping review aimed to (1) understand the possible influence of diet as a trigger of tics and (2) map out the existing studies documenting dietary interventions in children with TS. Current evidence suggests no single diet to benefit individuals with TS. However, reports from parents of children with TS suggest that certain allergens in food may exacerbate tic-related symptoms. For example, an increase in tics has been related to the consumption of caffeine and refined sugar. Moreover, oligoantigenic diets and sugar-free diets have been identified as significantly reducing tics. More research is urgently needed to develop more accurate guidance for parents and children with TS, as many have reported using dietary and nutritional supplements, despite the lack of evidence detailing any benefits, side effects and recommended doses.Peer reviewedFinal Accepted Versio

Expression quantitative trait loci are highly sensitive to cellular differentiation state

Blood cell development from multipotent hematopoietic stem cells to specialized blood cells is accompanied by drastic changes in gene expression for which the triggers remain mostly unknown. Genetical genomics is an approach linking natural genetic variation to gene expression variation, thereby allowing the identification of genomic loci containing gene expression modulators (eQTLs). In this paper, we used a genetical genomics approach to analyze gene expression across four developmentally close blood cell types collected from a large number of genetically different but related mouse strains. We found that, while a significant number of eQTLs (365) had a consistent “static” regulatory effect on gene expression, an even larger number were found to be very sensitive to cell stage. As many as 1,283 eQTLs exhibited a “dynamic” behavior across cell types. By looking more closely at these dynamic eQTLs, we show that the sensitivity of eQTLs to cell stage is largely associated with gene expression changes in target genes. These results stress the importance of studying gene expression variation in well-defined cell populations. Only such studies will be able to reveal the important differences in gene regulation between different ce

Bacterial microcompartment-directed polyphosphate kinase promotes stable polyphosphate accumulation in E. coli

Processes for the biological removal of phosphate from wastewater rely on temporary manipula-tion of bacterial polyphosphate levels by phased environmental stimuli. In E. coli polyphosphate levels are controlled via the polyphosphate-synthesizing enzyme polyphosphate kinase (PPK1) and exopolyphosphatases (PPX and GPPA), and are temporarily enhanced by PPK1 overexpression and reduced by PPX overexpression. We hypothesized that partitioning PPK1 from cytoplasmic exopoly phosphatases would increase and stabilize E. coli polyphosphate levels. Partitioning was achieved by co-expression of E. coli PPK1 fused with a microcompartment-targeting sequence and an artificial operon of Citrobacter freundii bacterial microcompartment genes. Encapsulation of targeted PPK1 resulted in persistent phosphate uptake and stably increased cellular polyphos-phate levels throughout cell growth and into the stationary phase, while PPK1 overexpression alone produced temporary polyphosphate increase and phosphate uptake. Targeted PPK1 increased polyphosphate in microcompartments eight-fold compared with non-targeted PPK1. Co-expression of PPX polyphosphatase with targeted PPK1 had little effect on elevated cellular polyphosphate levels because microcompartments retained polyphosphate. Co-expression of PPX with non-targeted PPK1 reduced cellular polyphosphate levels. Thus, subcellular compartmentali-zation of a polymerizing enzyme sequesters metabolic products from competing catabolism by preventing catabolic enzyme access. Specific application of this process to polyphosphate is of potential application for biological phosphate removal

Conceptualising the Global Forest Response to Liana Proliferation

Lianas are woody vines, rooted in the soil, and supported physically by trees. Lianas contribute to forest ecosystem functioning globally, but especially in the tropics and subtropics. However, prolific liana growth following heavy disturbance frequently affects subsequent recovery of forest tree diversity, biomass, structure, and function. Understanding this forest liana dynamic, and its sensitivity to climate and anthropogenic forces, is essential for worldwide forest restoration and climate change mitigation. Here, we synthesise the evidence for both positive and negative effects of lianas on forests and propose a framework that outlines the expected global response of forests to disturbance-induced liana proliferation. Emerging evidence suggests that lianas play a major role in both facilitating and delaying forest recovery following disturbance. At low levels of disturbance and/or where environmental conditions favour tree growth, lianas can facilitate forest recovery by protecting trees from extreme weather, fire, weed invasion and herbivory. However, under conditions where lianas proliferate beyond critical thresholds, positive feedbacks are expected to induce and sustain liana-dominated forest states that can endure for decades or even longer. We conceptualise alternative classes of forest recovery response to disturbance and describe measurement and modelling of liana thresholds.We identify four essential challenges for global change science relating to lianas: (1) incorporation of lianas and sapling stems into forest monitoring and tree stand measurements worldwide; (2) long-term experiments to determine variation in liana-tree competition, and potential drivers across forest successional gradients; (3) identification and prediction of liana thresholds and other alternative forest recovery response classes; and (4) dynamicmechanisticmodelling of forest recovery to determine regional and global variation within and among different recovery response classes, in relation to variation in potential drivers, liana feedbacks and their interactions. Addressing these challenges will determine the importance of lianas in shaping regional and global forest composition, recovery and dynamics

How Much Does Effortful Thinking Underlie Observers’ Reactions to Victimization?

From blaming to helping innocent victims, just-world research has revealed that observers react to victimization in a variety of ways. Recent research suggests that such responses to victimization require effortful thought, whereas other research has shown that people can react to these situations intuitively. Along with manipulating just-world threat, across seven experiments, we manipulated or measured participants’ level of mental processing before assessing judgments of victim derogation, blame, willingness to help, and ultimate justice reasoning. The effect of just-world threat on these responses held constant over a range of manipulations/measures, suggesting that the processes involved in maintaining a belief in a just world are not restricted to the rational, deliberative level of mental processing but also occur intuitively