A control strategy for a distributed power generation microgrid application with voltage and current controlled source converter

This paper presents a pseudodroop control structure integrated within a microgrid system through distributed power generation (DPG) modules capable to function in off-grid islanded, genset-connected, and grid-connected modes of operation. System efficiency has an important role in order to harvest the maximum available renewable energy from dc or ac sources while providing power backup capability. A control strategy is proposed in off-grid islanded mode method based on the microgrid line-frequency control as agent of communication for energy control between the DPG modules. A critical case is where the ac load demand could be lower than the available power from the photovoltaic solar array, where the battery bank can be overcharged with unrecoverable damage consequences. The DPG voltage-forming module controls the battery charge algorithm with a frequency-generator function, and the DPG current source module controls its output current through a frequency-detection function. The physical installation between DPG modules is independent, since no additional communication wiring is needed between power modules, which represent another integration advantage within the microgrid-type application

Nitric Oxide Synthase Encapsulation in Liposomes: A Potential Delivery Platform to (Nitric Oxide)-Deficient Targets

Nitric oxide (NO) is a freely diffusible, gaseous free radical, associated with many physiological and pathological processes: such as neuronal signaling, immune response and inflammatory response. In mammalian organisms, NO is produced from L-arginine in an NADPH-dependent reaction catalyzed by a family of nitric oxide synthase (NOS) enzymes. Typically, large NO fluctuations in biological systems under/over a critical limit is associated with problems that range from transient dysfunctions to severe chronic disease states. In this regard, we explore the development of a potential delivery and release method of nitric oxide to NO-deficient sites using liposomes as vehicles. Liposomes have already been used as effective nano-carriers. In this short communication, we report on the preparation and characterization of liposomes carrying a recombinant NOS enzyme. We report on the efficacy of using liposomes to carry NOS enzymes, and on the extent of preservation of native NOS structure and function. In addition to the characterization of liposome stability and recovery of enzymatic activity after encapsulation in liposomes, we also measured the NO production upon NOS stimulation. The NO release was monitored with a nitric oxide ultrasensitive electrochemical microsensor placed near NOS-carrying liposomes. This method of NOS-carrying liposomes shows the promise of potential development as a platform for targeted NO-delivery

Aspects of Integrability in N =4 SYM

Various recently developed connections between supersymmetric Yang-Mills theories in four dimensions and two dimensional integrable systems serve as crucial ingredients in improving our understanding of the AdS/CFT correspondence. In this review, we highlight some connections between superconformal four dimensional Yang-Mills theory and various integrable systems. In particular, we focus on the role of Yangian symmetries in studying the gauge theory dual of closed string excitations. We also briefly review how the gauge theory connects to Calogero models and open quantum spin chains through the study of the gauge theory duals of D3 branes and open strings ending on them. This invited review, written for Modern Physics Letters-A, is based on a seminar given at the Institute of Advanced Study, Princeton.Comment: Invited brief review for Mod. Phys. Lett. A based on a talk at I.A.S, Princeto

Poly(vinyl acetate)–clay hybrids prepared via emulsion polymerization, assisted by a nonionic surfactant

Hybrid materials containing poly(vinyl acetate) and montmorillonite (MMT) were prepared using an one-batch emulsion polymerization recipe, assisted by a nonionic surfactant. To explain the results of our experiments, a thorough investigation of the specific interactions between the compounds was done, in the wet as well as the dried state of the end-products. In dispersion, polymer–surfactant interactions were found to be driven by hydrophobic coupling into superficial (mixt) admicelles. Another important finding is that the amount of clay used in the recipes and its relative concentration with respect to the other reaction partners influences drastically the morphological units in the end-products. For low [MMT], well-defined, spherical particles are formed. At the other extreme, for high [MMT], production of polymeric, water-swollen aggregates is favored. A small amount of reformed MMT tactoids was detected in all casted hybrid films, indicating that most of the inorganic is dispersed in the organic phase

Some Properties of the Calogero-Sutherland Model with Reflections

We prove that the Calogero-Sutherland Model with reflections (the BC_N model) possesses a property of duality relating the eigenfunctions of two Hamiltonians with different coupling constants. We obtain a generating function for their polynomial eigenfunctions, the generalized Jacobi polynomials. The symmetry of the wave-functions for certain particular cases (associated to the root systems of the classical Lie groups B_N, C_N and D_N) is also discussed.Comment: 16 pages, harvmac.te

The SU(3) spin chain sigma model and string theory

The ferromagnetic integrable SU(3) spin chain provides the one loop anomalous dimension of single trace operators involving the three complex scalars of N=4 supersymmetric Yang-Mills. We construct the non-linear sigma model describing the continuum limit of the SU(3) spin chain. We find that this sigma model corresponds to a string moving with large angular momentum in the five-sphere in AdS_5xS^5. The energy and spectrum of fluctuations for rotating circular strings with angular momenta along three orthogonal directions of the five-sphere is reproduced as a particular case from the spin chain sigma model.Comment: 14 pages. Latex.v2: Misprints corrected. v3: Minor changes and improved details from journal versio

Collective skyrmion motion under the influence of an additional interfacial spin-transfer torque

Here we study the effect of an additional interfacial spin-transfer torque, as well as the well-established spin-orbit torque, on skyrmion collections - group of skyrmions dense enough that they are not isolated from one another - in ultrathin heavy metal / ferromagnetic multilayers, by comparing modelling with experimental results. Using a skyrmion collection with a range of skyrmion diameters, we study the dependence of the skyrmion Hall angle on diameter and velocity. As for an isolated skyrmion, a nearly-independent skyrmion Hall angle on skyrmion diameter for all skyrmion collection densities is reproduced by the model which includes interfacial spin-transfer torque. On the other hand, the skyrmion Hall angle change with velocity is significantly more abrupt compared to the isolated skyrmion case. This suggests that the effect of disorder on the collective skyrmion behavior is reduced compared to the isolated case. Our results further show the significance of the interfacial spin-transfer torque in ultrathin magnetic multilayers. Due to the good agreement with experiments, we conclude that the interfacial spin-transfer torque should be included in micromagnetic simulations for reproduction of experimental results.Comment: 18 pages, 4 figure

Interaction of magnetization and heat dynamics for pulsed domain wall movement with Joule heating

Pulsed domain wall movement is studied here in Ni80Fe20 nanowires on SiO2, using a fully integrated electrostatic, thermoelectric, and micromagnetics solver based on the Landau-Lifshitz- Bloch equation, including Joule heating, anisotropic magneto-resistance, and Oersted field contributions. During the applied pulse, the anisotropic magneto-resistance of the domain wall generates a dynamic heat gradient, which increases the current-driven velocity by up to 15%. Using a temperature-dependent conductivity, significant differences are found between the constant voltage-pulsed and constant current-pulsed domain wall movement: constant voltage pulses are shown to be more efficient at displacing domain walls whilst minimizing the increase in temperature, with the total domain wall displacement achieved over a fixed pulse duration having a maximum with respect to the driving pulse strength

Dynamics of a qubit coupled to a broadened harmonic mode at finite detuning

We study the dynamics of a symmetric two-level system strongly coupled to a broadened harmonic mode. Upon mapping the problem onto a spin-boson model with peaked spectral density, we show how analytic solutions can be obtained, at arbitrary detuning and finite temperatures, in the case of large Q-factors of the oscillator. In general {\em two} or more oscillation frequencies of the two-level particle are observed as a consequence of the entanglement with the oscillator. Our approximated analytical solution well agrees with numerical predictions obtained within the non-interacting blip approximation.Comment: 17 pages, 6 figure

Quantum corrections to the string Bethe ansatz

One-loop corrections to the energy of semiclassical rotating strings contain both analytic and non-analytic terms in the 't Hooft coupling. Analytic contributions agree with the prediction from the string Bethe ansatz based on the classical S-matrix, but in order to include non-analytic contributions quantum corrections are required. We find a general expression for the first quantum correction to the string Bethe ansatz.Comment: 12 pages. Latex. v2: Misprints corrected and references adde