Properties of Flares-Generated Seismic Waves on the Sun

The solar seismic waves excited by solar flares (``sunquakes'') are observed as circular expanding waves on the Sun's surface. The first sunquake was observed for a flare of July 9, 1996, from the Solar and Heliospheric Observatory (SOHO) space mission. However, when the new solar cycle started in 1997, the observations of solar flares from SOHO did not show the seismic waves, similar to the 1996 event, even for large X-class flares during the solar maximum in 2000-2002. The first evidence of the seismic flare signal in this solar cycle was obtained for the 2003 ``Halloween'' events, through acoustic ``egression power'' by Donea and Lindsey. After these several other strong sunquakes have been observed. Here, I present a detailed analysis of the basic properties of the helioseismic waves generated by three solar flares in 2003-2005. For two of these flares, X17 flare of October 28, 2003, and X1.2 flare of January 15, 2005, the helioseismology observations are compared with simultaneous observations of flare X-ray fluxes measured from the RHESSI satellite. These observations show a close association between the flare seismic waves and the hard X-ray source, indicating that high-energy electrons accelerated during the flare impulsive phase produced strong compression waves in the photosphere, causing the sunquake. The results also reveal new physical properties such as strong anisotropy of the seismic waves, the amplitude of which varies significantly with the direction of propagation. The waves travel through surrounding sunspot regions to large distances, up to 120 Mm, without significant decay. These observations open new perspectives for helioseismic diagnostics of flaring active regions on the Sun and for understanding the mechanisms of the energy release and transport in solar flares.Comment: 12 pages, 4 figures, submitted to Ap

Scaling properties in off equilibrium dynamical processes

In the present paper, we analyze the consequences of scaling hypotheses on dynamic functions, as two times correlations $C(t,t')$. We show, under general conditions, that $C(t,t')$ must obey the following scaling behavior $C(t,t') = \phi_1(t)^{f(\beta)}{\cal{S}}(\beta)$, where the scaling variable is $\beta=\beta(\phi_1(t')/\phi_1(t))$ and $\phi_1(t')$, $\phi_1(t)$ two undetermined functions. The presence of a non constant exponent $f(\beta)$ signals the appearance of multiscaling properties in the dynamics.Comment: 6 pages, no figure

Aging and memory effects in beta-hydrochinone-clathrate

The out-of-equilibrium low-frequency complex susceptibility of the orientational glass methanol(73%)-beta-hydrochinone-clathrate is studied using temperature-stop protocols in aging experiments . Although the material does not have a sharp glass transition aging effects including rejuvenation and memory are found at low temperatures. However, they turn out to be much weaker, however, than in conventional magnetic spin glasses.Comment: 5 pages RevTeX, 6 eps-figures include

Critical behavior of hard-core lattice gases: Wang-Landau sampling with adaptive windows

Critical properties of lattice gases with nearest-neighbor exclusion are investigated via the adaptive-window Wang-Landau algorithm on the square and simple cubic lattices, for which the model is known to exhibit an Ising-like phase transition. We study the particle density, order parameter, compressibility, Binder cumulant and susceptibility. Our results show that it is possible to estimate critical exponents using Wang-Landau sampling with adaptive windows. Finite-size-scaling analysis leads to results in fair agreement with exact values (in two dimensions) and numerical estimates (in three dimensions).Comment: 20 pages, 11 figure

Ring exchange, the Bose metal, and bosonization in two dimensions

Motivated by the high-T_c cuprates, we consider a model of bosonic Cooper pairs moving on a square lattice via ring exchange. We show that this model offers a natural middle ground between a conventional antiferromagnetic Mott insulator and the fully deconfined fractionalized phase which underlies the spin-charge separation scenario for high-T_c superconductivity. We show that such ring models sustain a stable critical phase in two dimensions, the *Bose metal*. The Bose metal is a compressible state, with gapless but uncondensed boson and ``vortex'' excitations, power-law superconducting and charge-ordering correlations, and broad spectral functions. We characterize the Bose metal with the aid of an exact plaquette duality transformation, which motivates a universal low energy description of the Bose metal. This description is in terms of a pair of dual bosonic phase fields, and is a direct analog of the well-known one-dimensional bosonization approach. We verify the validity of the low energy description by numerical simulations of the ring model in its exact dual form. The relevance to the high-T_c superconductors and a variety of extensions to other systems are discussed, including the bosonization of a two dimensional fermionic ring model

Synthesis and characterization of fluorogenic peptide substrate of HIV-1 protease based on fluorescence resonance energy transfer

Synthesis of fluorogenic peptide substrate of HIV-I protease Dns-SQNYPIVWL which corresponds to the p17/p24 cleavage site for HIV-l protease have been performed. This fluorogenic substrate was based on the fluorescence resonance energy transfer between donor – Trp residue, and acceptor – dansyl group in the intact peptide. Hydrolysis of substrate by recombinant HIV-I protease resulted in the time-dependent increase of Trp fluorescence and decrease of dansyl fluorescence measured at 350 and 500 nm, respectively, due to the break of resonance energy transfer between donor and acceptor fluorophors. Hydrolysis of fluorogenic peptide substrate was studied also by reversed phase HPLC and two peptide fragments after cleavage of substrate have been detected. Kinetic constants of hydrolysis for this fluorogenic peptide substrate by HIV-I protease were calculated from Lineweaver – Burk plots: KM - 29mkM, kcat =5.4 s⁻¹ and kcat / KM -180000 M⁻¹s⁻¹.Проведено хімічний синтез флюорогенного пептидного субстрату ВІЛ-1 протеази, що має структуру Dns-SQNYPIVWL і відповідає сайту розщеплення р17/р24 у gag-поліпротеіні вірусу імунодефіциту людини.Принцип використання даного субстрату базується на резонансному переносі енергії збудження між донором – залишком Trp і акцептором – дансильною групою. Встановлено, що гідроліз флюорогенного пептидного субстрату рекомбінантною ВІЛ-1 протеа­зою призводить до падіння інтенсивності флюоресценції дансильної групи і одночасного зростання триптофанової флюоресценції внаслідок порушення резонансного переносу енергії між донором і акцептором. За допомогою високоефективної рідинної хроматографії в оберненій фазі зафіксовано появу пептидів, які є продуктами гідролізу субстрату. Визначено кінетичні параметри гідролізу флюорогенного пептидного субстрату ВІЛ-1 протеазою: КМ – 29 мкМ, kcat– 5,4 с⁻¹ та kcat/KM – 180 000 M⁻¹c⁻¹.Проведен химический синтез флюорогенного пептидной субстрата ВИЧ -1 протеазы , имеющей структуру Dns – SQNYPIVWL и соответсвует сайтурасщепления р17/р24 в gag – полипротеини вируса иммунодефицита людини. Принцип использования данного субстрата базируется на резонансном переносе энергии возбуждения между донором - остатком Trp и акцептором – дансильною группой. Установлено, что гидролиз флюорогенного пептидной субстрата рекомбинантной ВИЧ -1 протеазой приводит к падению интенсивности флюоресценции дансильнои группы и одновременного роста триптофановой флюоресценции вследствие нарушения резонансного переноса энергии между донором и акцептором. С помощью высокоэффективной жидкостной хроматографии в обратной фазе зафиксировано появление пептидов, которые являются продуктами гидролиза субстрата. Определены кинетические параметры гидролиза флюорогенного пептидной субстрата ВИЧ -1 протеазой : КМ – 29 мкм , kcat - 5,4 с ⁻¹ и kcat / KM – 180 000 M⁻¹c ⁻¹

Magneto--Acoustic Energetics Study of the Seismically Active Flare of 15 February 2011

Multi--wavelength studies of energetic solar flares with seismic emissions have revealed interesting common features between them. We studied the first GOES X--class flare of the 24th solar cycle, as detected by the Solar Dynamics Observatory (SDO). For context, seismic activity from this flare (SOL2011-02-15T01:55-X2.2, in NOAA AR 11158) has been reported in the literature (Kosovichev, 2011; Zharkov et al., 2011). Based on Dopplergram data from the Helioseismic and Magnetic Imager (HMI), we applied standard methods of local helioseismology in order to identify the seismic sources in this event. RHESSI hard X-ray data are used to check the correlation between the location of the seismic sources and the particle precipitation sites in during the flare. Using HMI magnetogram data, the temporal profile of fluctuations in the photospheric line-of-sight magnetic field is used to estimate the magnetic field change in the region where the seismic signal was observed. This leads to an estimate of the work done by the Lorentz-force transient on the photosphere of the source region. In this instance this is found to be a significant fraction of the acoustic energy in the attendant seismic emission, suggesting that Lorentz forces can contribute significantly to the generation of sunquakes. However, there are regions in which the signature of the Lorentz-force is much stronger, but from which no significant acoustic emission emanates.Comment: Submitted to Solar Physic

On the existence of a Bose Metal at T=0

This paper aims to justify, at a microscopic level, the existence of a two-dimensional Bose metal, i.e. a metallic phase made out of Cooper pairs at T=0. To this end, we consider the physics of quantum phase fluctuations in (granular) superconductors in the absence of disorder and emphasise the role of two order parameters in the problem, viz. phase order and charge order. We focus on the 2-d Bose Hubbard model in the limit of very large fillings, i.e. a 2-d array of Josephson junctions. We find that the algebra of phase fluctuations is that of the Euclidean group $E_{2}$ in this limit, and show that the model is equivalent to two coupled XY models in (2+1)-d, one corresponding to the phase degrees of freedom, and the other the charge degrees of freedom. The Bose metal, then, is the phase in which both these degrees of freedom are disordered(as a result of quantum frustration). We analyse the model in terms of its topological excitations and suggest that there is a strong indication that this state represents a surface of critical points, akin to the gapless spin liquid states. We find a remarkable consistency of this scenario with certain low-T_c thin film experiments.Comment: 16 pages, 2 figure

Detecting fractions of electrons in the high-TcT_c cuprates

We propose several tests of the idea that the electron is fractionalized in the underdoped and undoped cuprates. These include the ac Josephson effect, and tunneling into small superconducting grains in the Coulomb blockade regime. In both cases, we argue that the results are qualitatively modified from the conventional ones if the insulating tunnel barrier is fractionalized. These experiments directly detect the possible existence of the chargon - a charge $e$ spinless boson - in the insulator. The effects described in this paper provide a means to probing whether the undoped cuprate (despite it's magnetism) is fractionalized. Thus, the experiments discussed here are complementary to the flux-trapping experiment we proposed in our earlier work(cond-mat/0006481).Comment: 7 pages, 5 figure

Ultratunable Quantum Frequency Conversion in Photonic Crystal Fiber

Quantum frequency conversion of single photons between wavelength bands is a key enabler to realizing widespread quantum networks. We demonstrate the quantum frequency conversion of a heralded 1551 nm photon to any wavelength within an ultrabroad (1226-1408 nm) range in a group-velocity-symmetric photonic crystal fiber, covering over 150 independent frequency bins. The target wavelength is controlled by tuning only a single pump laser wavelength. We find internal, and total, conversion efficiencies of 12(1)% and 1.4(2)%, respectively. For the case of converting 1551 to 1300 nm we measure a heralded g(2)(0)=0.25(6) for converted light from an input with g(2)(0)=0.034(8). We expect that this photonic crystal fiber can be used for myriad quantum networking tasks.</p