Synthesis, Characterization, Structural and Phase Analysis of Novel Antiferroelectric Solid Solution

Complex structural transformations or phase transitions and interest for high-power energy storage density makes silver niobate (AgNbO3) an interesting material. In AgNbO3, various phase transitions are mainly associated with orthorhombic phases (in cubic structure, parameter a=b=c, where in orthorhombic, a≠b≠c). These transitions dominate the electrical behavior of AgNbO3 to a significant level. Here, by substituting lead and zirconium in place of silver and niobium, the solid solution system (Ag(1-x)Pb(x))Nb(1-x)Zr(x)O3 (where 0 ≤ x ≤ 0.12) was formed in form of ceramic, using conventional solid state synthesis. The Dielectric behavior (ability of a material to store energy as a function of temperature) and structural behavior suggested that with the increase in composition of lead zirconate PbZrO3, all the transition temperature in AgNbO3 moved towards the lower temperature. The frequency dependent dispersion in one of the orthorhombic phases, M1 phase, became more prominent till x ≤ 0.04 after that it was beyond the detection limit. Investigations of X-ray diffraction revealed the presence of different orthorhombic symmetries at room temperature with the varying substitution of PbZrO3. Analysis of X-ray diffraction peaks confirmed the phase transition from Pmc21 to the mixture of Pbcm and Pmc21 space group to Pbcm with the increase in composition of PbZrO3. To further study the interesting phases of AgNbO3, single crystals were successfully grown. An optical microscopy technique called Polarized Light Microscopy result confirmed the existence of room temperature orthorhombic symmetries. To summarize, the aim of experiment is to understand the effect of structural changes over electrical properties. Faculty Supervisor:Dr. Zuo-Guang Ye, Department of Chemistry, Simon Fraser Universit

Phase resetting reveals network dynamics underlying a bacterial cell cycle

Genomic and proteomic methods yield networks of biological regulatory interactions but do not provide direct insight into how those interactions are organized into functional modules, or how information flows from one module to another. In this work we introduce an approach that provides this complementary information and apply it to the bacterium Caulobacter crescentus, a paradigm for cell-cycle control. Operationally, we use an inducible promoter to express the essential transcriptional regulatory gene ctrA in a periodic, pulsed fashion. This chemical perturbation causes the population of cells to divide synchronously, and we use the resulting advance or delay of the division times of single cells to construct a phase resetting curve. We find that delay is strongly favored over advance. This finding is surprising since it does not follow from the temporal expression profile of CtrA and, in turn, simulations of existing network models. We propose a phenomenological model that suggests that the cell-cycle network comprises two distinct functional modules that oscillate autonomously and couple in a highly asymmetric fashion. These features collectively provide a new mechanism for tight temporal control of the cell cycle in C. crescentus. We discuss how the procedure can serve as the basis for a general approach for probing network dynamics, which we term chemical perturbation spectroscopy (CPS)

Functional Roles of Pulsing in Genetic Circuits

A fundamental problem in biology is to understand how genetic circuits implement core cellular functions. Time-lapse microscopy techniques are beginning to provide a direct view of circuit dynamics in individual living cells. Unexpectedly, we are discovering that key transcription and regulatory factors pulse on and off repeatedly, and often stochastically, even when cells are maintained in constant conditions. This type of spontaneous dynamic behavior is pervasive, appearing in diverse cell types from microbes to mammalian cells. Here, we review recent work showing how pulsing is generated and controlled by underlying regulatory circuits and how it provides critical capabilities to cells in stress response, signaling, and development. A major theme is the ability of pulsing to enable time-based regulation analogous to strategies used in engineered systems. Thus, pulsatile dynamics is emerging as a central, and still largely unexplored, layer of temporal organization in the cell

Applying HCI Design Practices to the Development of the BrainEx User-Interface to Facilitate fNIRS Research

This project aims to develop a user-interface for BrainEx using HCI practices to enable fNIRS researchers to explore and analyze large datasets. The target users were identified through interviews with lab staff and developing user personas. Through iterative design, prototypes of increasing complexity and detail were designed, evaluated, and refined to satisfy user needs while fulfilling system requirements. The final application encompasses a user-friendly and tested interface that accomplishes the tool\u27s most essential functionality

Programmable base editing of zebrafish genome using a modified CRISPR-Cas9 system.

Precise genetic modifications in model animals are essential for biomedical research. Here, we report a programmable "base editing" system to induce precise base conversion with high efficiency in zebrafish. Using cytidine deaminase fused to Cas9 nickase, up to 28% of site-specific single-base mutations are achieved in multiple gene loci. In addition, an engineered Cas9-VQR variant with 5'-NGA PAM specificities is used to induce base conversion in zebrafish. This shows that Cas9 variants can be used to expand the utility of this technology. Collectively, the targeted base editing system represents a strategy for precise and effective genome editing in zebrafish.The use of base editing enables precise genetic modifications in model animals. Here the authors show high efficient single-base editing in zebrafish using modified Cas9 and its VQR variant with an altered PAM specificity

Stellar/BH Population in AGN Disks: Direct Binary Formation from Capture Objects in Nuclei Clusters

The Active Galatic Nuclei(AGN) disk has been proposed as a potential channel for the merger of binary black holes. The population of massive stars and black holes in AGN disks captured from the nuclei cluster plays a crucial role in determining the efficiency of binary formation and final merger rate within the AGN disks. In this paper, we investigate the capture process using analytical and numerical approaches. We discover a new constant integral of motion for one object's capture process. {Applying this result to the whole population of the nuclei cluster captured by the AGN disk, we find that the population of captured objects} depends on the angular density and eccentricity distribution of the nuclei clusters and is effectively independent of the radial density profile of the nuclei cluster and disk models. An isotropic nuclei cluster with thermal eccentricity distribution predicts a captured profile \dd N/\dd r\propto r^{-1/4}. The captured objects are found to be dynamically crowded within the disk. Direct binary formation right after the capture would be promising, especially for stars. The conventional migration traps that help pile up single objects in AGN disks for black hole mergers might not be required.Comment: Comments are welcom

Pulsatile Dynamics in the Yeast Proteome

The activation of transcription factors in response to environmental conditions is fundamental to cellular regulation. Recent work has revealed that some transcription factors are activated in stochastic pulses of nuclear localization, rather than at a constant level, even in a constant environment. In such cases, signals control the mean activity of the transcription factor by modulating the frequency, duration, or amplitude of these pulses. Although specific pulsatile transcription factors have been identified in diverse cell types, it has remained unclear how prevalent pulsing is within the cell, how variable pulsing behaviors are between genes, and whether pulsing is specific to transcriptional regulators or is employed more broadly. To address these issues, we performed a proteome-wide movie-based screen to systematically identify localization-based pulsing behaviors in Saccharomyces cerevisiae. The screen examined all genes in a previously developed fluorescent protein fusion library of 4,159 strains in multiple media conditions. This approach revealed stochastic pulsing in ten proteins, all transcription factors. In each case, pulse dynamics were heterogeneous and unsynchronized among cells in clonal populations. Pulsing is the only dynamic localization behavior that we observed, and it tends to occur in pairs of paralogous and redundant proteins. Taken together, these results suggest that pulsatile dynamics play a pervasive role in yeast and may be similarly prevalent in other eukaryotic species

Developing Biodiversity Protection Strategies for Urban Greenspace in Melbourne

The industry surrounding land management and conservation in Melbourne consists of many stakeholders from multiple organizations. The goal of this project was to increase the industry’s communication to better promote land management and consideration for biodiversity protection. To develop an understanding of those involved and the current state of land management, we conducted interviews with stakeholders and researched the region’s recent environmental history, and its current and past land management practices. Working with the Port Phillip EcoCentre, we developed a framework containing information on common problems and effective methods for combating issues we found among many groups. Finally, we proposed different ways the framework could be implemented in the future