[Cognitive-behavioural group therapy for insomnia: evaluation of the results after its implementation in a health department]

INTRODUCTION

Cognitive-behavioural therapy (CBT) is the preferred treatment in cases of chronic insomnia disorder in adults.

PATIENTS AND METHODS

Open pragmatic study of 32 patients after eight sessions of group CBT for insomnia.

RESULTS

Remission (insomnia severity index: 0-7 points) and response (insomnia severity index drops to > 8) were 31.3% and 46.9% at one month (n = 32) and 42.8% and 52.4% at one year (n = 21), respectively, with an effect size of 1.9 at one month and 2.3 at one year. At one month, 40.6% met the criteria for a case of insomnia (according to the insomnia symptoms questionnaire), and at one year, 19%, with a significant improvement in the symptoms at night and the consequences during the day. The questions of the Pittsburgh Sleep Quality Index on insomnia and sleep efficiency also improved. The pre-sleep arousal scale (n = 7) showed a shift from significant somatic and cognitive arousal to no arousal at one month. In the sleep diaries, total sleep time increased by an average of 53 minutes at one month (n = 14) and 76 minutes at one year (n = 10), with an increase of more than 10% in 71.4% of patients at one month and at one year, and an average sleep efficiency of more than 85%. The effect size for total sleep time and sleep efficiency was between 0.7 and 1.

CONCLUSIONS

Group CBT for insomnia appears to be an effective treatment option in a clinical setting.

Size quantization of Dirac fermions in graphene constrictions

Quantum point contacts are cornerstones of mesoscopic physics and central building blocks for quantum electronics. Although the Fermi wavelength in high-quality bulk graphene can be tuned up to hundreds of nanometres, the observation of quantum confinement of Dirac electrons in nanostructured graphene has proven surprisingly challenging. Here we show ballistic transport and quantized conductance of size-confined Dirac fermions in lithographically defined graphene constrictions. At high carrier densities, the observed conductance agrees excellently with the Landauer theory of ballistic transport without any adjustable parameter. Experimental data and simulations for the evolution of the conductance with magnetic field unambiguously confirm the identification of size quantization in the constriction. Close to the charge neutrality point, bias voltage spectroscopy reveals a renormalized Fermi velocity of ∼1.5 × 10(6) m s(-1) in our constrictions. Moreover, at low carrier density transport measurements allow probing the density of localized states at edges, thus offering a unique handle on edge physics in graphene devices.

Limitations to carrier mobility and phase-coherent transport in bilayer graphene

We present transport measurements on high-mobility bilayer graphene fully encapsulated in hexagonal boron nitride. We show two terminal quantum Hall effect measurements which exhibit full symmetry broken Landau levels at low magnetic fields. From weak localization measurements, we extract gate-tunable phase-coherence times τϕ as well as the inter- and intravalley scattering times τi and τ*, respectively. While τϕ is in qualitative agreement with an electron-electron interaction-mediated dephasing mechanism, electron spin-flip scattering processes are limiting τϕ at low temperatures. The analysis of τi and τ* points to local strain fluctuation as the most probable mechanism for limiting the mobility in high-quality bilayer graphene.

Fabrication of coupled graphene-nanotube quantum devices

We report on the fabrication and characterization of all-carbon hybrid quantum devices based on graphene and single-walled carbon nanotubes. We discuss both carbon nanotube quantum dot devices with graphene charge detectors and nanotube quantum dots with graphene leads. The devices are fabricated by chemical vapor deposition growth of carbon nanotubes and subsequent structuring of mechanically exfoliated graphene. We study the detection of individual charging events in the carbon nanotube quantum dot by a nearby graphene nanoribbon and show that they lead to changes of up to 20% of the conductance maxima in the graphene nanoribbon, acting as a well performing charge detector. Moreover, we discuss an electrically coupled graphene-nanotube junction, which exhibits a tunneling barrier with tunneling rates in the low GHz regime. This allows us to observe Coulomb blockade on a carbon nanotube quantum dot with graphene source and drain leads.

Electronic excited states in bilayer graphene double quantum dots

We report tunneling spectroscopy experiments on a bilayer graphene double quantum dot device that can be tuned by all-graphene lateral gates. The diameter of the two quantum dots are around 50 nm and the constrictions acting as tunneling barriers are 30 nm in width. The double quantum dot features additional energies on the order of 20 meV. Charge stability diagrams allow us to study the tunable interdot coupling energy as well as the spectrum of the electronic excited states on a number of individual triple points over a large energy range. The obtained constant level spacing of 1.75 meV over a wide energy range is in good agreement with the expected single-particle energy spacing in bilayer graphene quantum dots. Finally, we investigate the evolution of the electronic excited states in a parallel magnetic field.