Statistical Approach to Fuzzy Cognitive Maps

Fuzzy cognitive maps are studied from statistical standpoint. An analogy between these maps and linear regression and logistic regression models is drawn. Practical examples are also provided.Peer reviewe

The role of interparticle heterogeneities in the selenization pathway of Cu Zn Sn S nanoparticle thin films a real time study

Real time energy dispersive X ray diffraction EDXRD analysis has been utilized to observe the selenization of Cu Zn Sn S nanoparticle films coated from three nanoparticle populations Cu and Sn rich particles roughly 5 nm in size, Zn rich nanoparticles ranging from 10 to 20 nm in diameter, and a mixture of both types of nanoparticles roughly 1 1 by mass , which corresponds to a synthesis recipe yielding CZTSSe solar cells with reported total area efficiencies as high as 7.9 . The EDXRD studies presented herein show that the formation of copper selenide intermediates during the selenization of mixed particle films can be primarily attributed to the small, Cu and Sn rich particles. Moreover, the formation of these copper selenide phases represents the first stage of the CZTSSe grain growth mechanism. The large, Zn rich particles subsequently contribute their composition to form micrometer sized CZTSSe grains. These findings enable further development of a previously proposed selenization pathway to account for the roles of interparticle heterogeneities, which in turn provides a valuable guide for future optimization of processes to synthesize high quality CZTSSe absorber layer

The Catalytic Mechanism of a Natural Diels-Alderase Revealed in Molecular Detail

The Diels-Alder reaction, a [4 + 2] cycloaddition of a conjugated diene to a dienophile, is one of the most powerful reactions in synthetic chemistry. Biocatalysts capable of unlocking new and efficient Diels-Alder reactions would have major impact. Here we present a molecular-level description of the reaction mechanism of the spirotetronate cyclase AbyU, an enzyme shown here to be a bona fide natural Diels-Alderase. Using enzyme assays, X-ray crystal structures, and simulations of the reaction in the enzyme, we reveal how linear substrate chains are contorted within the AbyU active site to facilitate a transannular pericyclic reaction. This study provides compelling evidence for the existence of a natural enzyme evolved to catalyze a Diels-Alder reaction and shows how catalysis is achieved

Genetic transformation of Citrus sinensis with Citrus tristeza virus (CTV) derived sequences and reaction of transgenic lines to CTV infection

Transgenic Citrus sinensis (L.) Osb. plants, cvs. Valencia and Hamlin, expressing Citrus tristeza virus (CTV) derived sequences were obtained by genetic transformation. The gene constructs were pCTV-CP containing the 25 kDa major capsid protein gene (CTV-CP), pCTV-dsCP containing the same CTV-CP gene in an intron-spliced hairpin construct, and pCTV-CS containing a 559 nt conserved region of the CTV genome. The transgenic lines were identified by PCR and the transgene integration was confirmed by Southern blot. Transgene mRNA could be detected in most transgenic lines containing pCTV-CP or pCTV-CS transgene. The mRNA of pCTV-dsCP transgene was almost undetectable, with very light bands in most analyzed plants. The transgene transcription appears to be closely linked to the type of gene construct. The virus challenge assays reveals that all transgenic lines were infected. However, it was possible to identify propagated clones of transgenic plants of both cultivars studied with a low virus titer, with values similar to the non-inoculated plants (negative control). These results suggested that the transgenic plants present some level of resistance to virus replication. The higher number of clones with low virus titer and where mRNA could not be detected or was presented in a very light band was found for pCTV-dsCP-derived transgenic lines561162166CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informaçã

Synthetic RNA Silencing of Actinorhodin Biosynthesis in Streptomyces coelicolor A3(2)

We demonstrate the first application of synthetic RNA gene silencers in Streptomyces coelicolor A3(2). Peptide nucleic acid and expressed antisense RNA silencers successfully inhibited actinorhodin production. Synthetic RNA silencing was target-specific and is a new tool for gene regulation and metabolic engineering studies in Streptomyces.Peer reviewe

Scalable and Stable Ferroelectric Non-Volatile Memory at > 500 ∘^\circC

Non-volatile memory (NVM) devices that reliably operate at temperatures above 300 $^\circ$C are currently non-existent and remains a critically unmet challenge in the development of high-temperature (T) resilient electronics, necessary for many emerging, complex computing and sensing in harsh environments. Ferroelectric Al$_x$Sc$_{1-x}$N exhibits strong potential for utilization in NVM devices operating at very high temperatures (> 500 $^\circ$C) given its stable and high remnant polarization (PR) above 100 $\mu$C/cm$^2$ with demonstrated ferroelectric transition temperature (TC) > 1000 $^\circ$C. Here, we demonstrate an Al$_{0.68}$Sc$_{0.32}$N ferroelectric diode based NVM device that can reliably operate with clear ferroelectric switching up to 600 $^\circ$C with distinguishable On and Off states. The coercive field (EC) from the Pulsed I-V measurements is found to be -5.84 (EC-) and +5.98 (EC+) (+/- 0.1) MV/cm at room temperature (RT) and found to decrease with increasing temperature up to 600 $^\circ$C. The devices exhibit high remnant polarizations (> 100 $\mu$C/cm$^2$) which are stable at high temperatures. At 500 $^\circ$C, our devices show 1 million read cycles and stable On-Off ratio above 1 for > 6 hours. Finally, the operating voltages of our AlScN ferrodiodes are < 15 V at 600 $^\circ$C which is well matched and compatible with Silicon Carbide (SiC) based high temperature logic technology, thereby making our demonstration a major step towards commercialization of NVM integrated high-T computers.Comment: MS and S

Control and Characterization of Individual Grains and Grain Boundaries in Graphene Grown by Chemical Vapor Deposition

The strong interest in graphene has motivated the scalable production of high quality graphene and graphene devices. Since large-scale graphene films synthesized to date are typically polycrystalline, it is important to characterize and control grain boundaries, generally believed to degrade graphene quality. Here we study single-crystal graphene grains synthesized by ambient CVD on polycrystalline Cu, and show how individual boundaries between coalescing grains affect graphene's electronic properties. The graphene grains show no definite epitaxial relationship with the Cu substrate, and can cross Cu grain boundaries. The edges of these grains are found to be predominantly parallel to zigzag directions. We show that grain boundaries give a significant Raman "D" peak, impede electrical transport, and induce prominent weak localization indicative of intervalley scattering in graphene. Finally, we demonstrate an approach using pre-patterned growth seeds to control graphene nucleation, opening a route towards scalable fabrication of single-crystal graphene devices without grain boundaries.Comment: New version with additional data. Accepted by Nature Material

Ancestral Vascular Lumen Formation via Basal Cell Surfaces

The cardiovascular system of bilaterians developed from a common ancestor. However, no endothelial cells exist in invertebrates demonstrating that primitive cardiovascular tubes do not require this vertebrate-specific cell type in order to form. This raises the question of how cardiovascular tubes form in invertebrates? Here we discovered that in the invertebrate cephalochordate amphioxus, the basement membranes of endoderm and mesoderm line the lumen of the major vessels, namely aorta and heart. During amphioxus development a laminin-containing extracellular matrix (ECM) was found to fill the space between the basal cell surfaces of endoderm and mesoderm along their anterior-posterior (A-P) axes. Blood cells appear in this ECM-filled tubular space, coincident with the development of a vascular lumen. To get insight into the underlying cellular mechanism, we induced vessels in vitro with a cell polarity similar to the vessels of amphioxus. We show that basal cell surfaces can form a vascular lumen filled with ECM, and that phagocytotic blood cells can clear this luminal ECM to generate a patent vascular lumen. Therefore, our experiments suggest a mechanism of blood vessel formation via basal cell surfaces in amphioxus and possibly in other invertebrates that do not have any endothelial cells. In addition, a comparison between amphioxus and mouse shows that endothelial cells physically separate the basement membranes from the vascular lumen, suggesting that endothelial cells create cardiovascular tubes with a cell polarity of epithelial tubes in vertebrates and mammals

Revealing Correlation of Valence State with Nanoporous Structure in Cobalt Catalyst Nanoparticles by in Situ Environmental TEM

Simultaneously probing the electronic structure and morphology of materials at the nanometer or atomic scale while a chemical reaction proceeds is significant for understanding the underlying reaction mechanisms and optimizing a materials design. This is especially important in the study of nanoparticle catalysts, yet such experiments have rarely been achieved. Utilizing an environmental transmission electron microscope (ETEM) equipped with a differentially pumped gas cell, we are able to conduct nanoscopic imaging and electron energy loss spectroscopy (EELS) in situ for cobalt catalysts under reaction conditions. Analysis revealed quantitative correlation of the cobalt valence states to the particles' nanoporous structures. The in situ experiments were performed on nanoporous cobalt particles coated with silica while a 15 mTorr hydrogen environment was maintained at various temperatures (300-600\degreeC). When the nanoporous particles were reduced, the valence state changed from cobalt oxide to metallic cobalt and concurrent structural coarsening was observed. In situ mapping of the valence state and the corresponding nanoporous structures allows quantitatively analysis necessary for understanding and improving the mass activity and lifetime of cobalt-based catalysts, i.e., for Fischer-Tropsch synthesis that converts carbon monoxide and hydrogen into fuels, and uncovering the catalyst optimization mechanisms.Comment: ACS Nano, accepte