Distributed Optimal Frequency Control Considering a Nonlinear Network-Preserving Model

This paper addresses the distributed optimal frequency control of power systems considering a network-preserving model with nonlinear power flows and excitation voltage dynamics. Salient features of the proposed distributed control strategy are fourfold: i) nonlinearity is considered to cope with large disturbances; ii) only a part of generators are controllable; iii) no load measurement is required; iv) communication connectivity is required only for the controllable generators. To this end, benefiting from the concept of 'virtual load demand', we first design the distributed controller for the controllable generators by leveraging the primal-dual decomposition technique. We then propose a method to estimate the virtual load demand of each controllable generator based on local frequencies. We derive incremental passivity conditions for the uncontrollable generators. Finally, we prove that the closed-loop system is asymptotically stable and its equilibrium attains the optimal solution to the associated economic dispatch problem. Simulations, including small and large-disturbance scenarios, are carried on the New England system, demonstrating the effectiveness of our design

Tartronate Semialdehyde Reductase Defines a Novel Rate-Limiting Step in Assimilation and Bioconversion of Glycerol in Ustilago maydis

10.1371/journal.pone.0016438PLoS ONE61

Multi-functional anodes boost the transient power and durability of proton exchange membrane fuel cells.

Proton exchange membrane fuel cells have been regarded as the most promising candidate for fuel cell vehicles and tools. Their broader adaption, however, has been impeded by cost and lifetime. By integrating a thin layer of tungsten oxide within the anode, which serves as a rapid-response hydrogen reservoir, oxygen scavenger, sensor for power demand, and regulator for hydrogen-disassociation reaction, we herein report proton exchange membrane fuel cells with significantly enhanced power performance for transient operation and low humidified conditions, as well as improved durability against adverse operating conditions. Meanwhile, the enhanced power performance minimizes the use of auxiliary energy-storage systems and reduces costs. Scale fabrication of such devices can be readily achieved based on the current fabrication techniques with negligible extra expense. This work provides proton exchange membrane fuel cells with enhanced power performance, improved durability, prolonged lifetime, and reduced cost for automotive and other applications

A sugarcane mosaic virus vector for gene expression in maize

Zea mays L. ssp. mays (maize) is an important crop plant as well as model system for genetics and plant biology. The ability to select among different virus‐based platforms for transient gene silencing or protein expression experiments is expected to facilitate studies of gene function in maize and complement experiments with stable transgenes. Here, we describe the development of a sugarcane mosaic virus (SCMV) vector for the purpose of protein expression in maize. An infectious SCMV cDNA clone was constructed, and heterologous genetic elements were placed between the protein 1 (P1) and helper component‐proteinase (HC‐Pro) cistrons in the SCMV genome. Recombinant SCMV clones engineered to express green fluorescent protein (GFP), β‐glucuronidase (GUS), or bialaphos resistance (BAR) protein were introduced into sweet corn (Golden × Bantam) plants. Documentation of developmental time courses spanning maize growth from seedling to tasseling showed that the SCMV genome tolerates insertion of foreign sequences of at least 1,809 nucleotides at the P1/HC‐Pro junction. Analysis of insert stability showed that the integrity of GFP and BAR coding sequences was maintained longer than that of the much larger GUS coding sequence. The SCMV isolate from which the expression vector is derived is able to infect several important maize inbred lines, suggesting that this SCMV vector has potential to be a valuable tool for gene functional analysis in a broad range of experimentally important maize genotypes

N-(4-Fluorobenzoyl)-2-hydroxy-4-methyl­benzohydrazide

In the title compound, C15H13FN2O3, the aromatic rings are aligned at an angle of 10.15 (3)°. The mol­ecules are packed with π–π stacking inter­actions [mean inter­planar distances of 3.339 (2) and 3.357 (3) Å] and the crystal structure is stabilized by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds. An intramolecular N—H⋯O interaction also occurs

Folic Acid Supplementation Stimulates Notch Signaling and Cell Proliferation in Embryonic Neural Stem Cells

The present study investigated the effect of folic acid supplementation on the Notch signaling pathway and cell proliferation in rat embryonic neural stem cells (NSCs). The NSCs were isolated from E14–16 rat brain and grown as neurospheres in serum-free suspension culture. Individual cultures were assigned to one of 3 treatment groups that differed according to the concentration of folic acid in the medium: Control (baseline folic acid concentration of 4 mg/l), low folic acid supplementation (4 mg/l above baseline, Folate-L) and high folic acid supplementation (40 mg/l above baseline, Folate-H). NSCs were identified by their expression of immunoreactive nestin and proliferating cells by incorporation of 5'bromo-2'deoxyuridine. Cell proliferation was also assessed by methyl thiazolyl tetrazolium assay. Notch signaling was analyzed by real-time PCR and western blot analyses of the expression of Notch1 and hairy and enhancer of split 5 (Hes5). Supplementation of NSCs with folic acid increased the mRNA and protein expression levels of Notch1 and Hes5. Folic acid supplementation also stimulated NSC proliferation dose-dependently. Embryonic NSCs respond to folic acid supplementation with increased Notch signaling and cell proliferation. This mechanism may mediate the effects of folic acid supplementation on neurogenesis in the embryonic nervous system

Dielectric Properties and Maxwell-Wagner Relaxation of Compounds ACu3Ti4O12 (A=Ca,Bi2/3,Y2/3,La2/3)

We have studied the frequency and temperature dependences of permittivity and impedance of the compounds ACu3Ti4O12 A=Ca, Bi2/3, Y2/3, La2/3 in the ranges of 10−1–106 Hz and −150–200 °C. All compounds investigated display similar dielectric properties. Specifically, they all have a Debye-like relaxation and their dielectric constants are independent of frequency and temperature over a wide range. They all have two electrical responses in impedance formalism, indicating that there are two distinct contributions. We attribute them to grains and grain boundaries in the ceramic samples and explain the dielectric behaviors by Maxwell-Wagner relaxation arising at the interfaces between grains and their boundaries

SteC is a Salmonella kinase required for SPI-2-dependent F-actin remodelling

Salmonella enterica serovar Typhimurium (S. Typhimurium) replicates inside mammalian cells within membrane-bound compartments called Salmonella-containing vacuoles. Intracellular replication is dependent on the activities of several effector proteins translocated across the vacuolar membrane by the Salmonella pathogenicity island 2 (SPI-2)-type III secretion system (T3SS). This is accompanied by the formation in the vicinity of bacterial vacuoles of an F-actin meshwork, thought to be involved in maintaining the integrity of vacuolar membranes. In this study, we investigated the function of the SPI-2 T3SS effector SteC. An steC mutant strain was not defective for intracellular replication or attenuated for virulence in mice. However, the steC mutant was defective for SPI-2-dependent F-actin meshwork formation in host cells, although the vacuolar membranes surrounding mutant bacteria appeared to be normal. Expression of SteC in fibroblast cells following transfection caused extensive rearrangements of the F-actin cytoskeleton. Sequence analysis identified amino acid similarity between SteC and the human kinase Raf-1. A His-tagged SteC fusion protein had kinase activity in vitro and a point mutant lacking kinase activity was unable to induce F-actin rearrangements in vivo. We conclude that SPI-2-dependent F-actin meshwork formation depends on the kinase activity of SteC, which resembles more closely eukaryotic than prokaryotic kinases

A Gemini/GMOS Study of Intermediate Luminosity Early-Type Virgo Cluster Galaxies. I. Globular Cluster and Stellar Kinematics

We present a kinematic analysis of the globular cluster systems and diffuse stellar light of four intermediate luminosity (sub-$L^{\ast}$) early-type galaxies in the Virgo cluster based on Gemini/GMOS data. Our galaxy sample is fainter ($-23.8<M_K<-22.7$) than most previous studies, nearly doubling the number of galaxies in this magnitude range that now have GC kinematics. The data for the diffuse light extends to $4R_e$, and the data for the globular clusters reaches 8--$12R_e$. We find that the kinematics in these outer regions are all different despite the fact that these four galaxies have similar photometric properties, and are uniformly classified as "fast rotators" from their stellar kinematics within $1R_e$. The globular cluster systems exhibit a wide range of kinematic morphology. The rotation axis and amplitude can change between the inner and outer regions, including a case of counter-rotation. This difference shows the importance of wide-field kinematic studies, and shows that stellar and GC kinematics can change significantly as one moves beyond the inner regions of galaxies. Moreover, the kinematics of the globular cluster systems can differ from that of the stars, suggesting that the formation of the two populations are also distinct.Comment: 24 pages, 21 figures, 9 table, ApJ in pres

CaCu3Ti4O12: Low-Temperature Synthesis by Pyrolysis of an Organic Solution

The giant-dielectric-constant material CaCu3Ti4O12 (CCTO) has been synthesized by pyrolyzing an organic solution containing stoichiometric amounts of the metal cations, which is done at lower temperature and shorter reaction time than the conventional solid-state reaction. A stable solution was prepared by dissolving calcium nitrate, copper(II) nitrate, and titanium(IV) isopropoxide in 2-methoxyethanol. This solution was pyrolyzed and heat-treated to achieve single-phase CCTO. The phases, microstructures, and dielectric properties of intermediate and final samples were characterized by X-ray diffraction, scanning electron microscopy, and dielectric spectroscopy