Metal-insulator crossover in monolayer MoS2.

We report on transport measurements in monolayer MoS2devices, close to the bottom of the conduction band edge. These devices were annealedin situbefore electrical measurements. This allows us to obtain good ohmic contacts at low temperatures, and to measure precisely the conductivity and mobility via four-probe measurements. The measured effective mobility up toµeff= 180 cm2V-1s-1is among the largest obtained in CVD-grown MoS2monolayer devices. These measurements show that electronic transport is of the insulating type forσ≤ 1.4e2/handn≤ 1.7 × 1012cm-2, and a crossover to a metallic regime is observed above those values. In the insulating regime, thermally activated transport dominates at high temperature (T> 120 K). At lower temperatures, conductivity is driven by Efros-Schklovkii variable range hopping in all measured devices, with a universal and constant hopping prefactor, that is a clear indication that hopping is not phonon-mediated. At higher carrier density, and high temperature, the conductivity is well modeled by the Boltzmann equation for a non-interacting Fermi gas, taking into account both phonon and impurity scatterings. Finally, even if this apparent metal-insulator transition can be explained by phonon-related phenomena at high temperature, the possibility of a genuine 2D MIT cannot be ruled out, as we can observe a clear power-law diverging localization length close to the transition, and a one-parameter scaling can be realized.

Relationship between the serum concentrations of serotonin and lipids and aggression in dogs.

The serum concentrations of serotonin and lipids--triglycerides, total cholesterol, low density lipoprotein, high density lipoprotein and very low density lipoprotein--were determined in 18 normal dogs and 23 dogs diagnosed as aggressive on the basis of interviews with their owners and an assessment of their behaviour with reference to a canine overt aggression chart. The serum serotonin levels in the aggressive dogs were significantly lower than in the normal dogs (P<0.01), but the differences in serum lipids between the two groups were not statistically significant.

Relationships between serum serotonin and serum lipid levels, and aggression in horses.

Levels of serum serotonin and serum lipids--triglyceride, total cholesterol, low-density lipoprotein, high-density lipoprotein and very low-density lipoprotein, were determined in normal horses and horses diagnosed with aggression on the basis of a questionnaire survey. Blood serotonin levels in aggressive horses were found to be significantly lower than in non-aggressive horses (P < 0.01), but no association was found with respect to blood lipids.