Hydrogen-Induced Ultralow Optical Absorption and Mechanical Loss in Amorphous Silicon for Gravitational-Wave Detectors.

The sensitivity of gravitational-wave detectors is limited by the mechanical loss associated with the amorphous coatings of the detectors' mirrors. Amorphous silicon has higher refraction index and lower mechanical loss than current high-index coatings, but its optical absorption at the wavelength used for the detectors is at present large. The addition of hydrogen to the amorphous silicon network reduces both optical absorption and mechanical loss for films prepared under a range of conditions at all measured wavelengths and temperatures, with a particularly large effect on films grown at room temperature. The uptake of hydrogen is greatest in the films grown at room temperature, but still below 1.5 at.% H, which show an ultralow optical absorption (below 10 ppm) measured at 2000 nm for 500-nm-thick films. These results show that hydrogenation is a promising strategy to reduce both optical absorption and mechanical loss in amorphous silicon, and may enable fabrication of mirror coatings for gravitational-wave detectors with improved sensitivity.

In-plane thermal conductivity of sub-20 nm thick suspended mono-crystalline Si layers.

We measure the thermal conductivity of a 17.5-nm-thick single crystalline Si layer by using a suspended structure developed from a silicon-on-insulator wafer, in which the Si layer bridges the suspended platforms. The obtained value of 19 Wm(-1) K(-1) at room temperature represents a tenfold reduction with respect to bulk Si. This design paves the way for subsequent lateral nanostructuration of the layer with lithographic techniques, to define different geometries such as Si nanowires, nanostrips or phononic grids. As a proof of concept, nanostrips of 0.5 × 10 µm have been defined by focused ion beam (FIB) in the ultrathin Si layer. After the FIB cutting process with Ga ions at 30 kV and 100 pA, the measured thermal conductivity dramatically decreased to 1.7 Wm(-1) K(-1), indicating that the structure became severely damaged (amorphous). Re-crystallization of the structure was promoted by laser annealing while monitoring the Raman spectra. The thermal conductivity of the layer increased again to a value of 9.5 Wm(-1) K(-1) at room temperature, below that of the single crystalline material due to phonon scattering at the grain boundaries.

Evaluation of a heart failure knowledge questionnaire and its use in guiding the educational intervention.

INTRODUCTION AND OBJECTIVE: Patient education by nurses is a cornerstone of any heart failure (HF) program, but the models are widely heterogeneous and few specific instruments exist. Our objective is to evaluate our own questionnaire and its utility as a guide for educational intervention. METHODS: This work is a prospective cohort study of patients followed-up on in a specialized unit after diagnosis of HF. The intervention group received educational sessions guided according to their knowledge using the questionnaire and was compared to a group which received standard education. The validity and reliability of the questionnaire was evaluated. The utility of the educational model was determined by the primary composite endpoint of death and/or hospital admission or emergency care for HF. RESULTS: A total of 152 patients were included, 88 which received guided education and 64 which received standard education, with a mean follow-up time of 16±4 months. In the guided education group, the evaluation questionnaire score (qs) rose from 59% to 78.5% (p=0.018), which was associated with greater self-care (28.5-0.6*qs, p=0.04), a tendency toward better quality of life (51.1-1.1*qs, p=0.09), and adherence (5.02+0.04*qs, p=0.06), with acceptable reliability (Cronbach's alpha 0.75). The primary composite endpoint was met in 12 patients (13.6%) in the intervention group compared to 19 (29.7%) in the control group (hazard ratio: 0.46; 95% confidence interval: 0.24-0.88; p=0.019). Only educational level, age, NT-proBNP, and atrial fibrillation were predictors in the multivariate analysis. CONCLUSION: The HF knowledge questionnaire proposed is a valid, reliable tool and allows for quantifying learning. Its utility in guiding education requires a certain degree of skill from the patient that determines a group with better prognosis.