Synchronous neural oscillations in Parkinson’s disease: Variability and its potential network mechanisms

poster abstractRecent studies indicate that patterns of oscillatory synchronous activity in Basal Ganglia (BG) may be relevant to BG physiology and disorders, including Parkinson’s disease (PD). Oscillations in BG, in particular, in relation to motor control, are observed in different species, different conditions and different dopaminergic states (e.g., PD vs. normal). The rich membrane properties of BG neurons easily support oscillatory behavior. Correlations of oscillatory activity between different BG locations depend on the brain state and are dynamically organized. A general feature of BG oscillations is strong power and correlations of the β-band activity when no movement is performed and replacement of β with γ-band activity during movement. Dopamine-depleted state, such as PD, is marked by increase of oscillatory and synchronous activity, in particular in the β-band. This study explores the dynamical nature of these oscillations on short time-scales

Synchronous neural oscillations in Parkinson’s disease: Variability and its potential network mechanisms

poster abstractRecent studies indicate that patterns of oscillatory synchronous activity in Basal Ganglia (BG) may be relevant to BG physiology and disorders, including Parkinson’s disease (PD). Oscillations in BG, in particular, in relation to motor control, are observed in different species, different conditions and different dopaminergic states (e.g., PD vs. normal). The rich membrane properties of BG neurons easily support oscillatory behavior. Correlations of oscillatory activity between different BG locations depend on the brain state and are dynamically organized. A general feature of BG oscillations is strong power and correlations of the β-band activity when no movement is performed and replacement of β with γ-band activity during movement. Dopamine-depleted state, such as PD, is marked by increase of oscillatory and synchronous activity, in particular in the β-band. This study explores the dynamical nature of these oscillations on short time-scales

Horava Gravity and Gravitons at a Conformal Point

Recently Horava proposed a renormalizable gravity theory with higher derivatives by abandoning the Lorenz invariance in UV. Here, I study the Horava model at $\lambda=1/3$, where an anisotropic Weyl symmetry exists in the UV limit, in addition to the foliation-preserving diffeomorphism. By considering linear perturbations around Minkowski vacuum, I show that the scalar graviton mode is completely disappeared and only the usual tensor graviton modes remain in the physical spectrum. The existence of the UV conformal symmetry is unique to the theory with the detailed balance and it is quite probable that $\lambda=1/3$ be the UV fixed point. This situation is analogous to $\lambda=1$, which is Lorentz invariant in the IR limit and is believed to be the IR fixed point.Comment: Added comments and references, Accepted in GER

The horizon and its charges in the first order gravity

In this work the algebra of charges of diffeomorphisms at the horizon of generic black holes is analyzed within first order gravity. This algebra reproduces the algebra of diffeomorphisms at the horizon, (Diff(S^1)), without central extension

Role of dipolar and exchange interactions in the positions and widths of EPR transitions for the single-molecule magnets Fe8 and Mn12

We examine quantitatively the temperature dependence of the linewidths and line shifts in electron paramagnetic resonance experiments on single crystals of the single-molecule magnets Fe$_8$ and Mn$_{12}$, at fixed frequency, with an applied magnetic field along the easy axis. We include inter-molecular spin-spin interactions (dipolar and exchange) and distributions in both the uniaxial anisotropy parameter $D$ and the Land\'{e} $g$-factor. The temperature dependence of the linewidths and the line shifts are mainly caused by the spin-spin interactions. For Fe$_8$ and Mn$_{12}$, the temperature dependence of the calculated line shifts and linewidths agrees well with the trends of the experimental data. The linewidths for Fe$_8$ reveal a stronger temperature dependence than those for Mn$_{12}$, because for Mn$_{12}$ a much wider distribution in $D$ overshadows the temperature dependence of the spin-spin interactions. For Fe$_8$, the line-shift analysis suggests two competing interactions: a weak ferromagnetic exchange coupling between neighboring molecules and a longer-ranged dipolar interaction. This result could have implications for ordering in Fe$_8$ at low temperatures.Comment: published versio

Near-Horizon Conformal Symmetry and Black Hole Entropy in Any Dimension

Recently, Carlip proposed a derivation of the entropy of the two-dimensional dilatonic black hole by investigating the Virasoro algebra associated with a newly introduced near-horizon conformal symmetry. We point out not only that the algebra of these conformal transformations is not well defined on the horizon, but also that the correct use of the eigenvalue of the operator $L_0$ yields vanishing entropy. It has been shown that these problems can be resolved by choosing a different basis of the conformal transformations which is regular even at the horizon. We also show the generalization of Carlip's derivation to any higher dimensional case in pure Einstein gravity. The entropy obtained is proportional to the area of the event horizon, but it also depends linearly on the product of the surface gravity and the parameter length of a horizon segment in consideration. We finally point out that this derivation of black hole entropy is quite different from the ones proposed so far, and several features of this method and some open issues are also discussed.Comment: 14 pages, no figur

On the Thermodynamic Geometry of BTZ Black Holes

We investigate the Ruppeiner geometry of the thermodynamic state space of a general class of BTZ black holes. It is shown that the thermodynamic geometry is flat for both the rotating BTZ and the BTZ Chern Simons black holes in the canonical ensemble. We further investigate the inclusion of thermal fluctuations to the canonical entropy of the BTZ Chern Simons black holes and show that the leading logartithmic correction due to Carlip is reproduced. We establish that the inclusion of thermal fluctuations induces a non zero scalar curvature to the thermodynamic geometry.Comment: 1+17 pages, LaTeX, 4 eps figure

Broadening of band-gap in photonic crystals with optically saturated media

Due to strong absorption of the incident light, the media with high refractive index are considered restrictive for applications in photonic crystals (PhCs). The possibility to resolve this problem by optical saturation effectively minimizing the absorption of the PhC medium is discussed. Such approach might be promising for the significant broadening of the photonic band-gap.Comment: 10 page

Revised Phase Diagram of the Gross-Neveu Model

We confirm earlier hints that the conventional phase diagram of the discrete chiral Gross-Neveu model in the large N limit is deficient at non-zero chemical potential. We present the corrected phase diagram constructed in mean field theory. It has three different phases, including a kink-antikink crystal phase. All transitions are second order. The driving mechanism for the new structure of baryonic matter in the Gross-Neveu model is an Overhauser type instability with gap formation at the Fermi surface.Comment: Revtex, 12 pages, 15 figures; v2: Axis labelling in Fig. 9 correcte

Novel universality class of absorbing transitions with continuously varying critical exponents

The well-established universality classes of absorbing critical phenomena are directed percolation (DP) and directed Ising (DI) classes. Recently, the pair contact process with diffusion (PCPD) has been investigated extensively and claimed to exhibit a new type of critical phenomena distinct from both DP and DI classes. Noticing that the PCPD possesses a long-term memory effect, we introduce a generalized version of the PCPD (GPCPD) with a parameter controlling the memory effect. The GPCPD connects the DP fixed point to the PCPD point continuously. Monte Carlo simulations show that the GPCPD displays novel type critical phenomena which are characterized by continuously varying critical exponents. The same critical behaviors are also observed in models where two species of particles are coupled cyclically. We suggest that the long-term memory may serve as a marginal perturbation to the ordinary DP fixed point.Comment: 13 pages + 10 figures (Full paper version