947-114 Effects of Azimilide (NE-10064) on Cardiac K Channels

To understand the cellular mechanism of action of azimilide (Aziml, a novel class III antiarrhythmic agent, we studied its effegts on K currents in guinea pig and canine ventricular myocytes: slow (lKs) and rapid (lKr) delayed rectifier, inward rectifier (lKI) and transient outward (Ito) currents. To facilitate the quantification and comparison of drug potencies, the recording conditions were designed to “isolate” these K currents from other ionic currents and from each other. In particular, since it is difficult to separate IKrand IKsunder normal physiological conditions, a Na- and Ca-free external solution was used to dissect the two. This was confirmed by the selective action of dofetilide. Azim blocked IKsconcentration dependently (0.2–10 μM) and reversibly. Block was potentiated by more positive VtAt±30 mV, 2 μM Azim blocked IKsby 58±13% (n=6). Azim caused a time-dependent reduction of IKsduring depolarization and slowed IKsdeactivation, suggesting that block and unblock occurred mainly in the open state. Azim also blocked IKrconcentration dependently (0.1–2 μM)and reversibly. At -20 mV, 1 μM Azim blocked IKrby 86±10% (n=3). On the other hand, Ito(IC50> 10 μM.n=6) and IKI(IC50> 50 μM.n=2) were much less sensitive to Azim than IKror IKSIn conclusion, blockade of both delayed rectifiers makes important contributions to the class III action of Azim

Fast-Light in a Photorefractive Crystal for Gravitational Wave Detection

We demonstrate superluminal light propagation using two frequency multiplexed pump beams to produce a gain doublet in a photorefractive crystal of Ce:BaTiO3. The two gain lines are obtained by two-wave mixing between a probe field and two individual pump fields. The angular frequencies of the pumps are symmetrically tuned from the frequency of the probe. The frequency difference between the pumps corresponds to the separation of the two gain lines; as it increases, the crystal gradually converts from normal dispersion without detuning to an anomalously dispersive medium. The time advance is measured as 0.28 sec for a pulse propagating through a medium with a 2Hz gain separation, compared to the same pulse propagating through empty space. We also demonstrate directly anomalous dispersion profile using a modfied experimental configuration. Finally, we discuss how anomalous dispersion produced this way in a faster photorefractive crystal (such as SPS: Sn2P2S6) could be employed to enhance the sensitivity-bandwidth product of a LIGO type gravitational wave detector augmented by a White Light Cavity.Comment: 14 pages, 5 figure

NbSe3: Effect of Uniaxial Stress on the Threshold Field and Fermiology

We have measured the effect of uniaxial stress on the threshold field ET for the motion of the upper CDW in NbSe3. ET exhibits a critical behavior, ET ~ (1 - e/ec)^g, wher e is the strain, and ec is about 2.6% and g ~ 1.2. This ecpression remains valid over more than two decades of ET, up to the highest fields of about 1.5keV/m. Neither g nor ec is very sensitive to the impurity concentraction. The CDW transition temperature Tp decreases linearly with e at a rate dTp/de = -10K/%, and it does not show any anomaly near ec. Shubnikov de-Haas measurements show that the extremal area of the Fermi surface decreases with increasing strain. The results suggest that there is an intimate relationship between pinning of the upper CDW and the Fermiology of NbSe3.Comment: 4 pages, 5 figure

Properties of continuous Fourier extension of the discrete cosine transform and its multidimensional generalization

A versatile method is described for the practical computation of the discrete Fourier transforms (DFT) of a continuous function $g(t)$ given by its values $g_{j}$ at the points of a uniform grid $F_{N}$ generated by conjugacy classes of elements of finite adjoint order $N$ in the fundamental region $F$ of compact semisimple Lie groups. The present implementation of the method is for the groups SU(2), when $F$ is reduced to a one-dimensional segment, and for $SU(2)\times ... \times SU(2)$ in multidimensional cases. This simplest case turns out to result in a transform known as discrete cosine transform (DCT), which is often considered to be simply a specific type of the standard DFT. Here we show that the DCT is very different from the standard DFT when the properties of the continuous extensions of these two discrete transforms from the discrete grid points $t_j; j=0,1, ... N$ to all points $t \in F$ are considered. (A) Unlike the continuous extension of the DFT, the continuous extension of (the inverse) DCT, called CEDCT, closely approximates $g(t)$ between the grid points $t_j$. (B) For increasing $N$, the derivative of CEDCT converges to the derivative of $g(t)$. And (C), for CEDCT the principle of locality is valid. Finally, we use the continuous extension of 2-dimensional DCT to illustrate its potential for interpolation, as well as for the data compression of 2D images.Comment: submitted to JMP on April 3, 2003; still waiting for the referee's Repor

Smart subtitles for vocabulary learning

Language learners often use subtitled videos to help them learn. However, standard subtitles are geared more towards comprehension than vocabulary learning, as translations are nonliteral and are provided only for phrases, not vocabulary. This paper presents Smart Subtitles, which are interactive subtitles tailored towards vocabulary learning. Smart Subtitles can be automatically generated from common video sources such as subtitled DVDs. They provide features such as vocabulary definitions on hover, and dialog-based video navigation. In our pilot study with intermediate learners studying Chinese, participants correctly defined over twice as many new words in a post-viewing vocabulary test when they used Smart Subtitles, compared to dual Chinese-English subtitles. Learners spent the same amount of time watching clips with each tool, and enjoyed viewing videos with Smart Subtitles as much as with dual subtitles. Learners understood videos equally well using either tool, as indicated by self-assessments and independent evaluations of their summaries

Dirac Neutrino Dark Matter

We investigate the possibility that dark matter is made of heavy Dirac neutrinos with mass in the range [O(1) GeV- a few TeV] and with suppressed but non-zero coupling to the Standard Model Z as well as a coupling to an additional Z' gauge boson. The first part of this paper provides a model-independent analysis for the relic density and direct detection in terms of four main parameters: the mass, the couplings to the Z, to the Z' and to the Higgs. These WIMP candidates arise naturally as Kaluza-Klein states in extra-dimensional models with extended electroweak gauge group SU(2)_L* SU(2)_R * U(1). They can be stable because of Kaluza-Klein parity or of other discrete symmetries related to baryon number for instance, or even, in the low mass and low coupling limits, just because of a phase-space-suppressed decay width. An interesting aspect of warped models is that the extra Z' typically couples only to the third generation, thus avoiding the usual experimental constraints. In the second part of the paper, we illustrate the situation in details in a warped GUT model.Comment: 35 pages, 25 figures; v2: JCAP version; presentation and plots improved, results unchange

NMR Simulation of an Eight-State Quantum System

The propagation of excitation along a one-dimensional chain of atoms is simulated by means of NMR. The physical system used as an analog quantum computer is a nucleus of 133-Cs (spin 7/2) in a liquid crystalline matrix. The Hamiltonian of migration is simulated by using a special 7-frequency pulse, and the dynamics is monitored by following the transfer of population from one of the 8 spin energy levels to the other.Comment: 10 pages, 3 figure

Towards the Formalization of Fractional Calculus in Higher-Order Logic

Fractional calculus is a generalization of classical theories of integration and differentiation to arbitrary order (i.e., real or complex numbers). In the last two decades, this new mathematical modeling approach has been widely used to analyze a wide class of physical systems in various fields of science and engineering. In this paper, we describe an ongoing project which aims at formalizing the basic theories of fractional calculus in the HOL Light theorem prover. Mainly, we present the motivation and application of such formalization efforts, a roadmap to achieve our goals, current status of the project and future milestones.Comment: 9 page

Adapting SAM for CDF

The CDF and D0 experiments probe the high-energy frontier and as they do so have accumulated hundreds of Terabytes of data on the way to petabytes of data over the next two years. The experiments have made a commitment to use the developing Grid based on the SAM system to handle these data. The D0 SAM has been extended for use in CDF as common patterns of design emerged to meet the similar requirements of these experiments. The process by which the merger was achieved is explained with particular emphasis on lessons learned concerning the database design patterns plus realization of the use cases.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, pdf format, TUAT00

Quantum Simulations on a Quantum Computer

We present a general scheme for performing a simulation of the dynamics of one quantum system using another. This scheme is used to experimentally simulate the dynamics of truncated quantum harmonic and anharmonic oscillators using nuclear magnetic resonance. We believe this to be the first explicit physical realization of such a simulation.Comment: 4 pages, 2 figures (\documentstyle[prl,aps,epsfig,amscd]{revtex}); to appear in Phys. Rev. Let