Individual differences in the neuropsychopathology of addiction.

Drug addiction or substance-use disorder is a chronically relapsing disorder that progresses through binge/intoxication, withdrawal/negative affect and preoccupation/anticipation stages. These stages represent diverse neurobiological mechanisms that are differentially involved in the transition from recreational to compulsive drug use and from positive to negative reinforcement. The progression from recreational to compulsive substance use is associated with downregulation of the brain reward systems and upregulation of the brain stress systems. Individual differences in the neurobiological systems that underlie the processing of reward, incentive salience, habits, stress, pain, and executive function may explain (i) the vulnerability to substance-use disorder; (ii) the diversity of emotional, motivational, and cognitive profiles of individuals with substance-use disorders; and (iii) heterogeneous responses to cognitive and pharmacological treatments. Characterization of the neuropsychological mechanisms that underlie individual differences in addiction-like behaviors is the key to understanding the mechanisms of addiction and development of personalized pharmacotherapy

Topology effects on the heat capacity of mesoscopic superconducting disks

Phase transitions in superconducting mesoscopic disks have been studied over the H-T phase diagram through heat capacity measurement of an array of independent aluminium disks. These disks exhibit non periodic modulations versus H of the height of the heat capacity jump at the superconducting to normal transition. This behaviour is attributed to giant vortex states characterized by their vorticity L. A crossover from a bulk-like to a mesoscopic behaviour is demonstrated. $C_{\rm p}$ versus H plots exhibit cascades of phase transitions as L increases or decreases by one unity, with a strong hysteresis. Phase diagrams of giant vortex states inside the superconducting region are drawn in the vortex penetration and expulsion regimes and phase transitions driven by temperature between vortex states are thus predicted in the zero field cooled regime before being experimentally evidenced

Surface-Wave Dispersion Retrieval Method and Synthesis Technique for Bianisotropic Metasurfaces

We propose a surface-wave dispersion retrieval method and synthesis technique that applies to bianisotropic metasurfaces that are embedded in symmetric or asymmetric environments. Specifically, we use general zero-thickness sheet transition conditions to relate the propagation constants of surface-wave modes to the bianisotropic susceptibility components of the metasurface, which can themselves be directly related to its scattering parameters. It is then possible to either obtain the metasurface dispersion diagram from its known susceptibilities or, alternatively, compute the susceptibilities required to achieve a desired surface-wave propagation. The validity of the method is demonstrated by comparing its results to those obtained with exact dispersion relations of well known structures such as the propagation of surface plasmons on thin metallic films. In particular, this work reveals that it is possible to achieve surface-wave propagation only on one side of the metasurface either by superposition of symmetric and asymmetric modes in the case of anisotropic metasurfaces or by completely forbidding the existence of the surface wave on one side of the structure using bianisotropic metasurfaces

The radial acceleration relation is a natural consequence of the baryonic Tully-Fisher relation

Galaxies covering several orders of magnitude in stellar mass and a variety of Hubble types have been shown to follow the "Radial Acceleration Relation" (RAR), a relationship between $g_{\rm obs}$, the observed circular acceleration of the galaxy, and $g_{\rm bar}$, the acceleration due to the total baryonic mass of the galaxy. For accelerations above $10^{10}~{\rm m \, s}^{-2}$, $g_{\rm obs}$ traces $g_{\rm bar}$, asymptoting to the 1:1 line. Below this scale, there is a break in the relation such that $\rm g_{\rm obs} \sim g_{\rm bar}^{1/2}$. We show that the RAR slope, scatter and the acceleration scale are all natural consequences of the well-known baryonic Tully-Fisher relation (BTFR). We further demonstrate that galaxies with a variety of baryonic and dark matter (DM) profiles and a wide range of dark halo and galaxy properties (well beyond those expected in CDM) lie on the RAR if we simply require that their rotation curves satisfy the BTFR. We explore conditions needed to break this degeneracy: sub-kpc resolved rotation curves inside of "cored" DM-dominated profiles and/or outside $\gg 100\,$kpc could lie on BTFR but deviate in the RAR, providing new constraints on DM.Comment: 5 pages, submitted to MNRA

Ab initio theory of Fano resonances in plasmonic nanostructures and metamaterials

An ab initio theory for Fano resonances in plasmonic nanostructures and metamaterials is developed using Feshbach formalism. It reveals the role played by the electromagnetic modes and material losses in the system, and enables the engineering of Fano resonances in arbitrary geometries. A general formula for the asymmetric resonance in a non-conservative system is derived. The influence of the electromagnetic interactions on the resonance line shape is discussed and it is shown that intrinsic losses drive the resonance contrast, while its width is mostly determined by the coupling strength between the non-radiative mode and the continuum. The analytical model is in perfect agreement with numerical simulations.Comment: 13 pages, 5 figure

Multipolar Origin of the Unexpected Transverse Force Resulting from Two-Wave Interference

We propose a theoretical study on the electromagnetic forces resulting from the superposition of a TE and TM plane waves interacting with a sphere. Specifically, we first show that, under such an illumination condition, the sphere is subjected to a force transverse to the propagation direction of the waves. We then analyze the physical origin of this counter-intuitive behavior using a multipolar decomposition of the electromagnetic modes involved in that scattering process. This analysis reveals that interference effects, due to the two-wave illumination, lead to a Kerker-like asymmetric scattering behavior resulting in this peculiar transverse force

Random mixtures of polycyclic aromatic hydrocarbon spectra match interstellar infrared emission

The mid-infrared (IR; 5-15~$\mu$m) spectrum of a wide variety of astronomical objects exhibits a set of broad emission features at 6.2, 7.7, 8.6, 11.3 and 12.7 $\mu$m. About 30 years ago it was proposed that these signatures are due to emission from a family of UV heated nanometer-sized carbonaceous molecules known as polycyclic aromatic hydrocarbons (PAHs), causing them to be referred to as aromatic IR bands (AIBs). Today, the acceptance of the PAH model is far from settled, as the identification of a single PAH in space has not yet been successful and physically relevant theoretical models involving ``true'' PAH cross sections do not reproduce the AIBs in detail. In this paper, we use the NASA Ames PAH IR Spectroscopic Database, which contains over 500 quantum-computed spectra, in conjunction with a simple emission model, to show that the spectrum produced by any random mixture of at least 30 PAHs converges to the same 'kernel'-spectrum. This kernel-spectrum captures the essence of the PAH emission spectrum and is highly correlated with observations of AIBs, strongly supporting PAHs as their source. Also, the fact that a large number of molecules are required implies that spectroscopic signatures of the individual PAHs contributing to the AIBs spanning the visible, near-infrared, and far infrared spectral regions are weak, explaining why they have not yet been detected. An improved effort, joining laboratory, theoretical, and observational studies of the PAH emission process, will support the use of PAH features as a probe of physical and chemical conditions in the nearby and distant Universe