Power Factor Correction Boost Converter Based on the Three-State Switching Cell

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A DC-DC converter based on the three-state switching cell for high current and voltage step-down applications

This paper presents a pulsewidth modulation dc-dc nonisolated buck converter using the three-state switching cell, constituted by two active switches, two diodes, and two coupled inductors. Only part of the load power is processed by the active switches, reducing the peak current through the switches to half of the load current, as higher power levels can then be achieved by the proposed topology. The volume of reactive elements, i.e., inductors and capacitors, is also decreased since the ripple frequency of the output voltage is twice the switching frequency. Due to the intrinsic characteristics of the topology, total losses are distributed among all semiconductors. Another advantage of this converter is the reduced region for discontinuous conduction mode when compared to the conventional buck converter or, in other words, the operation range in continuous conduction mode is increased, as demonstrated by the static gain plot. The theoretical approach is detailed through qualitative and quantitative analyses by the application of the three-state switching cell to the buck converter operating in nonoverlapping mode $(D < 0.5)$. Besides, the mathematical analysis and development of an experimental prototype rated at 1 kW are carried out. The main experimental results are presented and adequately discussed to clearly identify its claimed advantages. © 1986-2012 IEEE.

Comparative analysis between overlapping and non-overlapping operation modes for the PWM buck converter using the three-state switching cell

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Conversor buck utilizando célula de comutação de três estados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Célula de comutação de três estados aplicada ao pré-regulador boost de estágio único e elevado fator de potência

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Disorder, oscillatory dynamics and state switching: the role of c-Myc

In this paper, using the intrinsically disordered oncoprotein Myc as an example, we present a mathematical model to help explain how protein oscillatory dynamics can influence state switching. Earlier studies have demonstrated that, while Myc overexpression can facilitate state switching and transform a normal cell into a cancer phenotype, its downregulation can reverse state-switching. A fundamental aspect of the model is that a Myc threshold determines cell fate in cells expressing p53. We demonstrate that a non-cooperative positive feedback loop coupled with Myc sequestration at multiple binding sites can generate bistable Myc levels. Normal quiescent cells with Myc levels below the threshold can respond to mitogenic signals to activate the cyclin/cdk oscillator for limited cell divisions but the p53/Mdm2 oscillator remains nonfunctional. In response to stress, the p53/Mdm2 oscillator is activated in pulses that are critical to DNA repair. But if stress causes Myc levels to cross the threshold, Myc inactivates the p53/Mdm2 oscillator, abrogates p53 pulses, and pushes the cyclin/cdk oscillator into overdrive sustaining unchecked proliferation seen in cancer. However, if Myc is downregulated, the cyclin/cdk oscillator is inactivated and the p53/Mdm2 oscillator is reset and the cancer phenotype is reversed. (C) 2015 Elsevier Ltd. All rights reserved.

Three-State Single-Molecule Naphthalenediimide Switch: Integration of a Pendant Redox Unit for Conductance Tuning

We studied charge transport through core-substituted naphthalenediimide (NDI) single-molecule junctions using the electrochemical STM-based break-junction technique in combination with DFT calculations. Conductance switching among three well-defined states was demonstrated by electrochemically controlling the redox state of the pendent diimide unit of the molecule in an ionic liquid. The electrical conductances of the dianion and neutral states differ by more than one order of magnitude. The potential-dependence of the charge-transport characteristics of the NDI molecules was confirmed by DFT calculations, which account for electrochemical double-layer effects on the conductance of the NDI junctions. This study suggests that integration of a pendant redox unit with strong coupling to a molecular backbone enables the tuning of charge transport through single-molecule devices by controlling their redox states.

Teachers reporting suspected child sexual abuse : results of a three-state study

Over 3000 cases of child sexual abuse are identified every year in Australia, but the real incidence is higher still. As a strategy to identify child sexual abuse, Australian States and Territories have enacted legislation requiring members of selected professions, including teachers, to report suspected cases. In addition, policy-based reporting obligations have been developed by professions, including the teaching profession. These legislative and industry-based developments have occurred in a context of growing awareness of the incidence and consequences of child sexual abuse. Teachers have frequent contact and close relationships with children, and possess expertise in monitoring changes in children’s behaviour. Accordingly, teachers are seen as being well-placed to detect and report suspected child sexual abuse. To date, however, there has been little empirical research into the operation of these reporting duties. The extent of teachers’ awareness of their duties to report child sexual abuse is unknown. Further, there is little evidence about teachers’ past reporting practice. Teachers’ duties to report sexual abuse, especially those in legislation, differ between States, and it is not known whether or how these differences affect reporting practice. This article presents results from the first large-scale Australian survey of teachers in three States with different reporting laws: New South Wales, Queensland, and Western Australia. The results indicate levels of teacher knowledge of reporting duties, reveal evidence about past reporting practice, and provide insights into anticipated future reporting practice and legal compliance. The findings have implications for reform of legislation and policy, training of teachers about the reporting of child sexual abuse, and enhancement of child protection.

Gelatine methacrylamide-based hydrogels : an alternative three-dimensional cancer cell culture system

Modern cancer research requires physiological, three-dimensional (3-D) cell culture platforms, wherein the physical and chemical characteristics of the extracellular matrix (ECM) can be modified. In this study, gelatine methacrylamide (GelMA)-based hydrogels were characterized and established as in vitro and in vivo spheroid-based models for ovarian cancer, reflecting the advanced disease stage of patients, with accumulation of multicellular spheroids in the tumour fluid (ascites). Polymer concentration (2.5-7% w/v) strongly influenced hydrogel stiffness (0.5±0.2kPa to 9.0±1.8kPa) but had little effect on solute diffusion. The diffusion coefficient of 70kDa fluorescein isothiocyanate (FITC)-labelled dextran in 7% GelMA-based hydrogels was only 2.3 times slower compared to water. Hydrogels of medium concentration (5% w/v GelMA) and stiffness (3.4kPa) allowed spheroid formation and high proliferation and metabolic rates. The inhibition of matrix metalloproteinases and consequently ECM degradability reduced spheroid formation and proliferation rates. The incorporation of the ECM components laminin-411 and hyaluronic acid further stimulated spheroid growth within GelMA-based hydrogels. The feasibility of pre-cultured GelMA-based hydrogels as spheroid carriers within an ovarian cancer animal model was proven and led to tumour development and metastasis. These tumours were sensitive to treatment with the anti-cancer drug paclitaxel, but not the integrin antagonist ATN-161. While paclitaxel and its combination with ATN-161 resulted in a treatment response of 33-37.8%, ATN-161 alone had no effect on tumour growth and peritoneal spread. The semi-synthetic biomaterial GelMA combines relevant natural cues with tunable properties, providing an alternative, bioengineered 3-D cancer cell culture in in vitro and in vivo model systems.

Thermodynamic analysis of three state denaturation of Peanut Agglutinin

Peanut Agglutinin (PNA) is a homotetrameric protein with a very unusual open quaternary structure. During denaturation, it first dissociates into a molten globule like state, which subsequently undergoes complete denaturation. Urea denaturation of PNA at neutral pH has been studied by intrinsic fluorescence spectroscopy and has been fitted to a three state model, A(4) double left right arrow 4I double left right arrow 4U, to get all the relevant thermodynamic parameters. Urea denaturation leads to continuous red shift of wavelength maxima. The molten globule like state is formed in a short range of urea concentration. Refolding of the denatured PNA has been attempted by intrinsic fluorescence study. Refolding by instantaneous dilution shows the occurrence of the formation of an intermediate at a relatively rapid rate, within few seconds. The transition from PNA tetramer to molten globule like state is found to have a Delta G value of similar to 33 kcal/mole while it is similar to 8 kcal/mole for the transition from molten globule like state to a completely denatured state. This in turn indicates that the tetramerization in PNA contributes significantly to the stability of the oligomer.

Activity–Composition Relations in the Nickel Oxide–Magnesium Oxide System at 1300 K by the Solid-State Galvanic Cell Technique

The activity of NiO in NiO-MgO rock salt solid solution has been measured at 1300 K by employing a solid-state galvanic cell: Pt,Ni+ NiO||(CaO)ZrO2||Ni + (Nix,Mgl-x)O, Pt. A high-density tube of Zr02-15 mol% CaO has been used as the solid electrolyte for the emf measurements. The activities of the component oxides in the rock salt solid solution exhibit negative deviation from ideality at the temperature of investigation. The solid solution obeys regular solution behavior at 1300 K. The value of the regular solution parameter is found to be -12000 ((l000) J mol-1. The composition dependence of ΔGEx obtained in this study agrees reasonably well with the calorimetric data reported in the literature for NiO-MgO solid solution.

System Dy-Fe-O: thermodynamic properties of ternary oxides using Calvet calorimetry and solid-state electrochemical cell

The enthalpy increments and the standard molar Gibbs energies of formation-of DyFeO3(s) and Dy3Fe5O12(s) have been measured using a Calvet micro-calorimeter and a solid oxide galvanic cell, respectively. A co-operative phase transition, related to anti-ferromagnetic to paramagnetic transformation, is apparent. from the heat capacity data for DyFeO3 at similar to 648 K. A similar type of phase transition has been observed for Dy3Fe5O12 at similar to 560 K which is related to ferrimagnetic to paramagnetic transformation. Enthalpy increment data for DyFeO3(s) and Dy3Fe5O12(s), except in the vicinity of the second-order transition, can be represented by the following polynomial expressions:{H(0)m(T) - H(0)m(298.15 K)) (Jmol(-1)) (+/-1.1%) = -52754 + 142.9 x (T (K)) + 2.48 x 10(-3) x (T (K))(2) + 2.951 x 10(6) x (T (K))(-1); (298.15 less than or equal to T (K) less than or equal to 1000) for DyFeO3(s), and {H(0)m(T) - H(0)m(298.15 K)} (Jmol(-1)) (+/-1.2%) = -191048 + 545.0 x (T - (K)) + 2.0 x 10(-5) x (T (K))(2) + 8.513 x 10(6) x (T (K))(-1); (208.15 less than or equal to T (K) less than or equal to 1000)for Dy3Fe5O12(s). The reversible emfs of the solid-state electrochemical cells: (-)Pt/{DyFeO3(s) + Dy2O3(s) + Fe(s)}/YDT/CSZ//{Fe(s) + Fe0.95O(s)}/Pt(+) and (-)Pt/{Fe(s) + Fe0.95O(s)}//CSZ//{DyFeO3(s) + Dy3Fe5O12(s) + Fe3O4(s)}/Pt(+), were measured in the temperature range from 1021 to 1250 K and 1035 to 1250 K, respectively. The standard Gibbs energies of formation of solid DyFeO3 and Dy3Fe5O12 calculated by the least squares regression analysis of the data obtained in the present study, and data for Fe0.95O and Dy2O3 from the literature, are given by Delta(f)G(0)m(DyFeO3,s)(kJmol(-1))(+/-3.2)= -1339.9 + 0.2473 x (T(K)); (1021 less than or equal to T (K) less than or equal to 1548)and D(f)G(0)m(Dy3Fe5O12,s) (kJmol(-1)) (+/-3.5) = -4850.4 + 0.9846 x (T (K)); (1035 less than or equal to T (K) less than or equal to 1250) The uncertainty estimates for Delta(f)G(0)m include the standard deviation in the emf and uncertainty in the data taken from the literature. Based on the thermodynamic information, oxygen potential diagram and chemical potential diagrams for the system Dy-Fe-O were developed at 1250 K. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

Triplet excited electronic state switching induced by hydrogen bonding: A transient absorption spectroscopy and time-dependent DFT study

The solvent plays a decisive role in the photochemistry and photophysics of aromatic ketones. Xanthone (XT) is one such aromatic ketone and its triplet-triplet (T-T) absorption spectra show intriguing solvatochromic behavior. Also, the reactivity of XT towards H-atom abstraction shows an unprecedented decrease in protic solvents relative to aprotic solvents. Therefore, a comprehensive solvatochromic analysis of the triplet-triplet absorption spectra of XT was carried out in conjunction with time dependent density functional theory using the ad hoc explicit solvent model approach. A detailed solvatochromic analysis of the T-T absorption bands of XT suggests that the hydrogen bonding interactions are different in the corresponding triplet excited states. Furthermore, the contributions of non-specific and hydrogen bonding interactions towards differential solvation of the triplet states in protic solvents were found to be of equal magnitude. The frontier molecular orbital and electron density difference analysis of the T-1 and T-2 states of XT indicates that the charge redistribution in these states leads to intermolecular hydrogen bond strengthening and weakening, respectively, relative to the S-0 state. This is further supported by the vertical excitation energy calculations of the XT-methanol supra-molecular complex. The intermolecular hydrogen bonding potential energy curves obtained for this complex in the S-0, T-1, and T-2 states support the model. In summary, we propose that the different hydrogen bonding mechanisms exhibited by the two lowest triplet excited states of XT result in a decreasing role of the n pi* triplet state, and are thus responsible for its reduced reactivity towards H-atom abstraction in protic solvents. (C) 2016 AIP Publishing LLC.

HIGH-TEMPERATURE SUPERCONDUCTOR, YBA2CU3O7-X AS ALL-SOLID-STATE LITHIUM CELL

The utility of the high-temperature superconductor, YBa2Cu3O7-x as the cathode material for an all-solid-state lithium cell has been examined. The capacity of YBa2Cu3O7-x is 223 mA h g-1 and the discharge efficiency is > 92%. Measurements of a.c. impedance show that the charge-transfer resistance at the interface of the electrolyte/cathode is very low and increases with the depth-of-discharge of the battery. Studies using X-ray photoelectron spectroscopy (XPS) reveal that the cathode becomes doped with Li+ ions as the cell discharges.

Analysis of three marine fish cell lines by RAPD assay

We tested the applicability of the random amplified polymorphic deoxyribonucleic acid (RAPD) analysis for identification of three marine fish cell lines FG. SPH, and RSBK and as a possible tool to detect cross-contamination. Sixth commercial 10-mer RAPD primers were tested on the cell lines and on samples collected from individual fish. The results obtained showed that the cell lines could be identified to the correspondent species on the basis of identical Patterns produced by 35-48% of the primers tested. the total mean similarity indices for cell lines versus correspondent species of individual fish ranged from 0.825 to 0.851. indicating the existence of genetic variation in these cell lines in relation to the species of their origin. Also, four primers, which gave a monomorphic hand pattern within species/line, but different among the species/line, were obtained. These primers can be useful for identification of these cell lines and for characterization of the genetic variation of these cell lines in relation to the species of their origin. This supported the use of RAPD analysis as an effective tool in species identification and cross-contamination test among different cell lines.