Criteria of interplanetary parameters causing intense magnetic storms (Dst less than -100nT)

Ten intense storms occurred during the 500 days of August 16, 1978 to December 28, 1979. From the analysis of ISEE-3 field and plasma data, it is found that the interplanetary cause of these storms are long-duration, large and negative IMF B sub Z events, associated with interplanetary duskward-electric fields greater than 5 mV/m. Because a one-to-one relationship was found between these interplanetary events and intense storms, it is suggested that these criteria can, in the future, be used as predictors of intense storms by an interplanetary monitor such as ISEE-3. These B sub Z events are found to occur in association with large amplitudes of the IMF magnitude within two days after the onset of either high-speed solar wind streams or of solar wind density enhancement events, giving important clues to their interplanetary origin. Some obvious possibilities will be discussed. The close proximity of B sub Z events and magnetic storms to the onset of high speed streams or density enhancement events is in sharp contrast to interplanetary Alfven waves and HILDCAA events previously reported, and thus the two interplanetary features corresponding geomagnetic responses can be thought of as being complementary in nature. An examination of opposite polarity B sub Z events with the same criteria show that their occurrence is similar both in number as well as in their relationship to interplanetary disturbances, and that they lead to low levels of geomagnetic activity

Insight into the Calmodulin and DREAM Protein Complex Interaction, Mechanism and Function

DREAM (Downstream regulatory element antagonistic modulator) is a neuronal calcium sensor which has been shown to modulate gene expression as well as being involved in numerous neuronal processes. In this report, we show that association of calcium bound calmodulin (CaM) with DREAM is mediated by a short amphipathic amino acid sequence located between residues 29 and 44 on DREAM N-termini The association of CaM with a peptide analogous to DREAM(29-44) or to full length DREAM protein is calcium dependent with the dissociation constant of 136 nM and 3.4 ?M, respectively. Thermodynamic and kinetic studies show that the observed decrease in affinity for the native protein is due to electrostatic interaction between the basic N-terminus and an acidic surface on DREAM. These results are further supported by molecular dynamic simulations, circular dichroism and binding studies. Additionally, in fluorescence anisotropy decay measurements, a rotational correlation time of 10.8 ns for a complex of CaM with a DREAM(29-44) peptide was observed, supporting a wraparound semi- spherical model with 1:1 stoichiometry. Furthermore, the interaction between a IEDANS labeled CaM construct with DREAM is best modeled as a heterotetramer. The CaM:DREAM heterotetramer adopts an elongated conformation with correlation time of 45 ns in the presence of Ca2+. We also demonstrate that association of CaM with DREAM eliminates the nonspecific interaction of DREAM with the DRE dsDNA sequence of human prodynorphin gene. The presented work provides an molecular insight into the CaM:DREAM complex and its potential role in modulation of gene expression

Sparse Transfer Learning for Interactive Video Search Reranking

Visual reranking is effective to improve the performance of the text-based video search. However, existing reranking algorithms can only achieve limited improvement because of the well-known semantic gap between low level visual features and high level semantic concepts. In this paper, we adopt interactive video search reranking to bridge the semantic gap by introducing user's labeling effort. We propose a novel dimension reduction tool, termed sparse transfer learning (STL), to effectively and efficiently encode user's labeling information. STL is particularly designed for interactive video search reranking. Technically, it a) considers the pair-wise discriminative information to maximally separate labeled query relevant samples from labeled query irrelevant ones, b) achieves a sparse representation for the subspace to encodes user's intention by applying the elastic net penalty, and c) propagates user's labeling information from labeled samples to unlabeled samples by using the data distribution knowledge. We conducted extensive experiments on the TRECVID 2005, 2006 and 2007 benchmark datasets and compared STL with popular dimension reduction algorithms. We report superior performance by using the proposed STL based interactive video search reranking.Comment: 17 page

On the estimates of the ring current injection and decay

In the context of the space weather predictions, forecasting ring current strength (and of the Dst index) based on the solar wind upstream conditions is of specific interest for predicting the occurrence of geomagnetic storms. In the present paper, we have studied separately its two components: the Dst injection and decay. In particular, we have verified the validity of the Burton's equation for estimating the ring current energy balance using the equatorial electric merging field instead of the original parameter V Bs (V is the solar wind speed and Bs is the southward component of the Interplanetary Magnetic Field, IMF). Then, based on this equation, we have used the phasespace method to determine the best-fit approximations for the ring current injection and decay as functions of the equatorial merging electric field (Em). Results indicate that the interplanetary injection is statistically higher than in previous estimations using V Bs . Specifically, weak but not-null ring current injection can be observed even during northward IMF, when previous studies considered it to be always zero. Moreover, results about the ring current decay indicate that the rate of Dst decay is faster than its predictions derived by using V Bs . In addition, smaller quiet time ring current and solar wind pressure corrections are contributing to Dst estimates obtained by Em instead of V Bs . These effects are compensated, so that the statistical Dst predictions using the equatorial electric merging field or using V Bs are about equivalent

Programming in CUDA for Kepler and Maxwell Architecture

Since the first version of CUDA was launch, many improvements were made in GPU computing. Every new CUDA version included important novel features, turning this architecture more and more closely related to a typical parallel High Performance Language. This tutorial will present the GPU architecture and CUDA principles, trying to conceptualize novel features included by NVIDIA, such as dynamics parallelism, unified memory and concurrent kernels. This text also includes some optimization remarks for CUDA programs

PBC design for voltage regulation in buck converters with parametric uncertainties

This paper addresses the problem of voltage output regulation in DC Buck converters from the passivity-based control (PBC) point of view. The PBC takes advantage of the natural port-Hamiltonian representation of dynamic equations of the buck converter, to design a feedback controller with proportionalintegral gains, that allows to guarantee stability conditions in the sense of Lyapunov for closed-loop operation. The design of the controller is based on the incremental dynamic model of the buck converter. The PBC approach considers unknown resistive loads in the controller design without degrading the dynamic performance of the controller. In addition, the proposed approach allows to design a controller regardless the buck parameters (capacitance and inductance) which makes it robust to parametric uncertainties. Sliding planes and classical PI control methods are used for comparing the proposed PBC method. All simulations have been performed in MATLAB software by using SymPowerSystems library

Mitigating fluctuations of wind power generation using superconducting magnetic energy storage: A passivity-based approach

Abstract This paper presents the control of the active and reactive power of a superconducting magnetic energy storage (SMES) system for compensating fluctuations of a power system with high penetration of wind energy during extreme scenarios of wind gusts. The wind energy conversion system (WECS) is a Type-A turbine with squirrel cage induction generator (SCIG) and a capacitor bank. A passivity-based proportional-integral control (PI-PBC) is used that controls the power transfer of the SMES system to the power grid. The proposed controller is designed with two main objectives: First, to deliver (or absorb) a suitable active power to (or from) the power system, and second, to regulate the voltage of the WECS. The proposed PI-PBC guarantees asymptotically stability in closed-loop and exploits the advantages of the proportional-integral (PI) actions. Also, it presents a superior performance when it is compared to a conventional PI controller and a proportional feedback linearization controller. Simulation results carried-out in MATLAB/SIMULINK demonstrate the advantages of the proposed methodology. © 2019 IEEE

Persistence of neuronal representations through time and damage in the hippocampus

How do neurons encode long-term memories? Bilateral imaging of neuronal activity in the mouse hippocampus reveals that, from one day to the next, ~40% of neurons change their responsiveness to cues, but thereafter only 1% of cells change per day. Despite these changes, neuronal responses are resilient to a lack of exposure to a previously completed task or to hippocampus lesions. Unlike individual neurons, the responses of which change after a few days, groups of neurons with inter- and intrahemispheric synchronous activity show stable responses for several weeks. The likelihood that a neuron maintains its responsiveness across days is proportional to the number of neurons with which its activity is synchronous. Information stored in individual neurons is relatively labile, but it can be reliably stored in networks of synchronously active neurons