L. Nitti

Steady-State Visual Evoked Potentials and Phase Synchronization in Migraine Patients

We investigate phase synchronization in EEG recordings from migraine patients. We use the analytic signal technique, based on the Hilbert transform, and find that migraine brains are characterized by enhanced alpha band phase synchronization in the presence of visual stimuli. Our findings show that migraine patients have an overactive regulatory mechanism that renders them more sensitive to external stimuli.

Effects of levetiracetam vs topiramate and placebo on visually evoked phase synchronization changes of alpha rhythm in migraine

OBJECTIVE Recent theories about migraine pathogenesis have outlined an abnormal central processing of sensory signals, also suggested by an abnormal pattern of EEG hyper-synchronization under visual stimulation. The aim of the present study was to test the efficacy of topiramate and levetiracetam vs placebo in a double blind project observing the effects of the three treatments on the EEG synchronization in the alpha band under sustained flash stimulation. METHODS Forty-five migraine without aura outpatients (MO) were selected and randomly assigned to 100mg topiramate, 1000 mg levetiracetam or placebo treatment. In addition, 24 non-migraine healthy controls were submitted to EEG analysis. The EEG was recorded by 19 channels: flash stimuli with a luminosity of 0.2J were delivered, in a frequency range from 3 to 30 Hz. We evaluated the phase synchronization index, that we previously applied in migraine, after EEG signals filtering in the alpha band. Our approach was based on the Hilbert transform. RESULTS Both levetiracetam and topiramate significantly decreased migraine frequency, compared with placebo. MO patients displayed increased alpha-band phase synchronization as an effect of stimulus frequency; on the other hand the stimuli had an overall desynchronizing effect on control subjects. The phase synchronization index separates the two stages, before and after the treatment, only for levetiracetam, at stimulus frequencies of 9, 18, 24 and 27 Hz. CONCLUSIONS An abnormal alpha band synchronization under visual stimuli was confirmed in migraine; this phenomenon was reversed by levetiracetam preventive treatment. SIGNIFICANCE These results confirmed in humans the inhibiting action of levetiracetam on neuronal hyper-synchronization.

A realistic model of the semileptonic decays of beauty

Abstract A realistic calculation of the semileptonic decays of B-mesons, which depends in an essential manner on the Kobayashi-Maskawa matrix elements Vb→c and Vb→u only, is presented. A very good fit to the experimental lepton spectrum is obtained for | V b→u V b→c | 2 = 0.10 ± 0.06 , and from the world average for the B-lifetime (τB = 1.04 ± 0.15 ps), Vb→c = (5.9 ± 0.4) × 10−2 and Vb→u = (1.9 ± 0.5) × 10−2 are derived.

Leave-one-out prediction error of systolic arterial pressure time series under paced breathing.

In this paper, we consider systolic arterial pressure time series from healthy subjects and chronic heart failure patients, undergoing paced respiration, and show that different physiological states and pathological conditions may be characterized in terms of predictability of time series signals from the underlying biological system. We model time series by the regularized least-squares approach and quantify predictability by the leave-one-out error. We find that the entrainment mechanism connected to paced breath, that renders the arterial blood pressure signal more regular and thus more predictable, is less effective in patients, and this effect correlates with the seriousness of the heart failure. Using a Gaussian kernel, so that all orders of nonlinearity are taken into account, the leave-one-out error separates controls from patients (probability less than 10(-7)), and alive patients from patients for whom cardiac death occurred (probability less than 0.01).

Phase shifts of synchronized oscillators and the systolic-diastolic blood pressure relation

We study the phase-synchronization properties of systolic and diastolic arterial pressure in healthy subjects. We find that delays in the oscillatory components of the time series depend on the frequency bands that are considered, in particular we find a change of sign in the phase shift going from the very low frequency band to the high frequency band. This behavior should reflect a collective behavior of a system of nonlinear interacting elementary oscillators. We prove that some models describing such systems, e.g., the Winfree and the Kuramoto models, offer a clue to this phenomenon. For these theoretical models there is a linear relationship between phase shifts and the difference of natural frequencies of oscillators and a change of sign in the phase shift naturally emerges.

Deterministic annealing as a jet clustering algorithm in hadronic collisions

We show that a general purpose clusterization algorithm, deterministic annealing, can be adapted to the problem of jet identification in particle production by high energy collisions. In particular, we consider the problem of jet searching in events generated at hadronic colliders. Deterministic annealing is able to reproduce the results obtained by traditional jet algorithms and to exhibit a higher degree of flexibility.

Jet analysis by deterministic annealing

Abstract We perform a comparison of two jet clusterization algorithms. The first one is the standard Durham algorithm and the second one is a global optimization scheme, Deterministic Annealing , often used in clusterization problems, and adapted to the problem of jet identification in particle production by high energy collisions; in particular we study hadronic jets in WW production by high energy e + e − scattering. Our results are as follows. First, we find that the two procedures give basically the same output as far as the particle clusterization is concerned. Second, we find that the increase of CPU time with the particle multiplicity is much faster for the Durham jet clustering algorithm in comparison with Deterministic Annealing. Since this result follows from the higher computational complexity of the Durham scheme, it should not depend on the particular process studied here and might be significant for jet physics at LHC as well.

A MONTE CARLO PROGRAM FOR GENERATING HADRONIC FINAL STATES IN ELECTRON POSITRON ANNIHILATIONS

Titleofprogram: EPOS particlesin thefinal state(30 or 40particlesarenot uncommon at W= 35 GeV) [1]. Thecomplexityof this phenomenonneeds Cataloguenumber:ACDM a theoreticalframework for describingand understandingthe basicphysicalmechanisminvolved. Programobtainablefrom: CPC ProgramLibrary, Queen’sUniThe presentprogramis aneventgeneratorof hadronicfinal versityof Belfast,N. Ireland(seeapplicationform in thisissue) statesbasedon the Fire-String theory and hasbeen shownto reproducevery well all thefeaturesexperimentallyobserved[2]. Computers on which the program is operable: CDC 7600/CYBER875/VAX 780 Methodofsolution The program is based on the Monte Carlo method and its Operatingsystem:7000 SCOPE2.1.4 (CDC)/NOS-BELevel generateseventswith weight= I using the Fire-String theory 587/VAX-VMS [2]. The notion of Fire-String comesfrom the descriptionof hadronicmatterin termsof boundstates(bags)of quarksand Programminglanguage:FORTRAN antiquarksin the theoretical framework named Quark-Geometro-Dynamics[3]. In this approachto the dynamicsof high High speedstoragerequired: 50 Kwords on CDC’s anda peak energyphysicsonecandefinea highly excitedquark—antiquark valueof 240 Kwords on theVAX boundstatewith a cylindricalstructure,calledFire-string(FS). Theevolutionof theFSandits decaymodesareresponsiblefor No. of bits in a word: 60 (CDC), 32 (VAX) thedepositionof hadronsin thefinal states. All these physical ideas have been implementedin the No. of lines in combinedprogram and testdeck: 3938 presentprogram.

Is the gluon hiding under the third jet

Abstract The emergence of three-jet events in hadronic final states in electron-positron annihilation at CM energies W > 15 GeV is explained in terms of a new decay mechanism for the elongated quark-antiquark structures, called “Fire-Strings”.

Fire-string decay at high energies: Baryon-antibaryon production in e+e- annihilation

Abstract Baryon-antibaryon production in electron-positron annihilation at high energies is calculated in the framework of quark geometrodynamics and compared with existing experimental information. Good agreement is found between experiments and theory.