Mott Insulators of Ultracold Fermionic Alkaline Earth Atoms: Underconstrained Magnetism and Chiral Spin Liquid

We study Mott insulators of fermionic alkaline earth atoms, described by Heisenberg spin models with enhanced SU(N) symmetry. In dramatic contrast to SU(2) magnetism, more than two spins are required to form a singlet. On the square lattice, the classical ground state is highly degenerate and magnetic order is thus unlikely. In a large-N limit, we find a chiral spin liquid ground state with topological order and Abelian fractional statistics. We discuss its experimental detection. Chiral spin liquids with non-Abelian anyons may also be realizable with alkaline earth atoms.Comment: 4 pages, 2 figures, 1 table. Minor changes from v2. Final published versio

Multiphoton Effects Enhanced Due to Ultrafast Photon-Number Fluctuations

Multi-photon processes are the essence of nonlinear optics. Optical harmonics generation and multi-photon absorption, ionization, polymerization or spectroscopy are widely used in practical applications. Generally, the rate of an n-photon effect scales as the n-th order autocorrelation function of the incident light, which is high for light with strong photon-number fluctuations. Therefore `noisy' light sources are much more efficient for multi-photon effects than coherent sources with the same mean power, pulse duration and repetition rate. Here we generate optical harmonics of order 2-4 from bright squeezed vacuum (BSV), a state of light consisting of only quantum noise with no coherent component. We observe up to two orders of magnitude enhancement in the generation of optical harmonics due to ultrafast photon-number fluctuations. This feature is especially important for the nonlinear optics of fragile structures where the use of a `noisy' pump can considerably increase the effect without overcoming the damage threshold

Paediatric non-alcoholic fatty liver disease: impact on patients and mothers' quality of life

Background: Non-alcoholic fatty liver disease (NAFLD) is one of the causes of fatty liver in adults and is currently the primary form of chronic liver disease in children and adolescents. However, the psychological outcome (i.e. the behavioural problems that can in turn be related to psychiatric conditions, like anxiety and mood disorders, or lower quality of life) in children and adolescents suffering of NAFLD has not been extensively explored in the literature. Objectives: The present study aims at evaluating the emotional and behavioural profile in children suffering from NAFLD and the quality of life in their mothers. Patients and Methods: A total of 57 children (18 females/39 males) with NAFLD were compared to 39 age-matched control children (25 females/14 males). All participants were submitted to the following psychological tools to assess behavior, mood, and anxiety: the Multidimensional Anxiety Scale for Children (MASC), the Child Behavior Checklist (CBCL), and the Children's Depression Inventory (CDI). Moreover, the mothers of 40 NAFLD and 39 control children completed the World Health Organization Quality of Life-BREF (WHOQOL-BREF) questionnaire. Results: NAFLD children scored significantly higher as compared to control children in MASC (P = 0.001) and CDI total (P < 0.001) scales. The CBCL also revealed significantly higher scores for NAFLD children in total problems (P = 0.046), internalizing symptoms (P = 0.000) and somatic complaints (P < 0.001). The WHOQOL-BREF revealed significantly lower scores for the mothers of NAFLD children in the overall perception of the quality of life (P < 0.001), and in the "relationships" domain (P = 0.023). Conclusions: Increased emotional and behavioural problems were detected in children with NAFLD as compared to healthy control children, together with an overall decrease in their mothers' quality of life. These results support the idea that these patients may benefit from a psychological intervention, ideally involving both children and parents, whose quality of life is likely negatively affected by this disease

Symmetry reductions of a particular set of equations of associativity in twodimensional topological field theory

The WDVV equations of associativity arising in twodimensional topological field theory can be represented, in the simplest nontrivial case, by a single third order equation of the Monge-Ampe`re type. By investigating its Lie point symmetries, we reduce it to various nonlinear ordinary differential equations, and we obtain several new explicit solutions.Comment: 10 pages, Latex, to appear in J. Phys. A: Math. Gen. 200

Metabolic reprogramming of murine cardiomyocytes during autophagy requires the extracellular nutrient sensor decorin.

The extracellular matrix is a master regulator of tissue homeostasis in health and disease. Here we examined how the small, leucine-rich, extracellular matrix proteoglycan decorin regulates cardiomyocyte metabolism during fasting in vivo. First, we validated in Dcn-/- mice that decorin plays an essential role in autophagy induced by fasting. High-Throughput metabolomics analyses of cardiac tissue in Dcn-/- mice subjected to fasting revealed striking differences in the hexosamine biosynthetic pathway resulting in aberrant cardiac O-β-N-Acetylglycosylation as compared with WT mice. Functionally, Dcn-/- mice maintained cardiac function at a level comparable with nonfasted animals whereas fasted WT mice showed reduced ejection fraction. Collectively, our results suggest that reduced sensing of nutrient deprivation in the absence of decorin preempts functional adjustments of cardiac output associated with metabolic reprogramming. © 2018 Gubbiotti et al

Dipolar ground state of planar spins on triangular lattices

An infinite triangular lattice of classical dipolar spins is usually considered to have a ferromagnetic ground state. We examine the validity of this statement for finite lattices and in the limit of large lattices. We find that the ground state of rectangular arrays is strongly dependent on size and aspect ratio. Three results emerge that are significant for understanding the ground state properties: i) formation of domain walls is energetically favored for aspect ratios below a critical valu e; ii) the vortex state is always energetically favored in the thermodynamic limit of an infinite number of spins, but nevertheless such a configuration may not be observed even in very large lattices if the aspect ratio is large; iii) finite range approximations to actual dipole sums may not provide the correct ground sta te configuration because the ferromagnetic state is linearly unstable and the domain wall energy is negative for any finite range cutoff.Comment: Several short parts have been rewritten. Accepted for publication as a Rapid Communication in Phys. Rev.

Enhanced self-administration of the CB1 receptor agonist WIN55,212-2 in olfactory bulbectomized rats: evaluation of possible serotonergic and dopaminergic underlying mechanisms

Depression has been associated with drug consumption, including heavy or problematic cannabis use. According to an animal model of depression and substance use disorder comorbidity, we combined the olfactory bulbectomy (OBX) model of depression with intravenous drug self-administration procedure to verify whether depressive-like rats displayed altered voluntary intake of the CB1 receptor agonist WIN55,212-2 (WIN, 12.5 μg/kg/infusion). To this aim, olfactory-bulbectomized (OBX) and sham-operated (SHAM) Lister Hooded rats were allowed to self-administer WIN by lever-pressing under a continuous [fixed ratio 1 (FR-1)] schedule of reinforcement in 2 h daily sessions. Data showed that both OBX and SHAM rats developed stable WIN intake; yet, responses in OBX were constantly higher than in SHAM rats soon after the first week of training. In addition, OBX rats took significantly longer to extinguish the drug-seeking behavior after vehicle substitution. Acute pre-treatment with serotonin 5HT1B receptor agonist, CGS-12066B (2.5-10 mg/kg), did not significantly modify WIN intake in OBX and SHAM Lister Hooded rats. Furthermore, acute pre-treatment with CGS-12066B (10 and 15 mg/kg) did not alter responses in parallel groups of OBX and SHAM Sprague Dawley rats self-administering methamphetamine under higher (FR-2) reinforcement schedule with nose-poking as operandum. Finally, dopamine levels in the nucleus accumbens (NAc) of OBX rats did not increase in response to a WIN challenge, as in SHAM rats, indicating a dopaminergic dysfunction in bulbectomized rats. Altogether, our findings suggest that a depressive-like state may alter cannabinoid CB1 receptor agonist-induced brain reward function and that a dopaminergic rather than a 5-HT1B mechanism is likely to underlie enhanced WIN self-administration in OBX rats