Experimental evidence of thermoelastic damping in silicon tuning fork

AbstractMiniaturized resonators are critical components in many application fields such as sensing, communication and time reference. One critical parameter for these resonators is their quality factor. In this study, various silicon tuning fork resonators with an AlN piezoelectric actuation have been fabricated. Depending on their resonance frequency, quality factors between 10'000 and 25'000 were obtained. It is shown that for frequencies between 30 and 80 kHz thermoelastic damping (TED) is the dominant mechanism that limits the Q-factor

Thickness dependence of the properties of highly c-axis textured AlN thin films

The influence of film thickness on the material properties of aluminum nitride (AlN) thin films deposited on Pt(111) electrodes has been investigated experimentally by means of x-ray diffraction, dielectric response, atomic force microscopy, interferometry measurement of effective d(33), and residual stress measurement. The thickness was varied between 35 nm and 2 mum. Full width at mid-height of the rocking curve decreased from 2.60 to 1.14degrees, rms roughness increased from 3.8 to 18.6 Angstrom, the effective d(33), namely d(33f), from 2.75 to 5.15 pm/V. The permittivity epsilon(AIN) was stable at 10.2, whereas the dielectric losses decreased from 1% to 0.1%. The breakdown electric field under do voltages varied between 4.0 and 5.5 MV/cm. (C) 2004 American Vacuum Society

Rivastigmine in Parkinson's Disease Dementia with Orthostatic Hypotension

Objective: The purpose of this study was to evaluate if the cognitive benefit of rivastigmine is affected by the presence of orthostatic hypotension (OH) in patients with Parkinson's disease dementia (PDD). Methods: We conducted a post hoc analysis on 1,047 patients with PDD from 2 randomized controlled trials comparing rivastigmine versus placebo at week 24 (n = 501) and rivastigmine patch versus capsule at week 76 (n = 546). A drop ≥ 20 mm Hg in systolic blood pressure (SBP) or ≥ 10 in diastolic blood pressure (DBP) upon standing classified subjects as OH positive (OH+); otherwise, OH negative (OH-). The primary end point was the Alzheimer's Disease Assessment Scale - Cognitive subscale (ADAS-Cog) at week 24 and the Mattis Dementia Rating Scale (MDRS) at week 76, using intention-to-treat with retrieved dropout at week 24 and observed cases at week 76, consistent with the original analyses. Results: Overall safety was comparable between OH+ (n = 288, 27.5%) and OH- (n = 730, 69.7%), except for higher frequency of syncope (9.2%) in the OH+ placebo arm. The placebo-adjusted effect of rivastigmine on ADAS-Cog at week 24 was 5.6 ± 1.2 for OH+ and 1.9 ± 0.9 in OH- (p = 0.0165). Among subjects with OH, the MDRS change from baseline at week 76 was higher for rivastigmine capsules versus patch (10.6 ± 2.9 vs -1.5 ± 3.0, p = 0.031). The overall prevalence of OH was lower for rivastigmine than placebo at week 24 (28.3% vs 44.6%, p = 0.0476). Interpretation: The cognitive benefit from rivastigmine is larger in patients with PDD with OH, possibly mediated by a direct antihypotensive effect. ANN NEUROL 2020

Cocaine use in Europe - A multi-centre study: Patterns of use in different groups

The study investigates patterns of cocaine powder and crack cocaine use in different groups in nine European cities. A multi-centre cross-sectional study was conducted in Barcelona, Budapest, Dublin, Hamburg, London, Paris, Rome, Vienna, and Zurich. Data were collected by structured face-to-face interviews. The sample comprises 1,855 cocaine users out of three subgroups: 632 cocaine users in addiction treatment, mainly maintenance treatment; 615 socially marginalised cocaine users not in treatment; and 608 socially integrated cocaine users not in treatment. Measurements: Use of cocaine powder, crack cocaine and other substances in the last 30 days, routes of administration, and lifetime use of cocaine powder and crack cocaine. The marginalised group showed the highest intensity of cocaine use, of heroin use and of multiple substance use. Of the integrated group, 95 per cent snorted cocaine powder, while in the two other groups, injecting was quite prevalent, but with huge differences between the cities. Ninety-six per cent of all participants had used at least one other substance in addition to cocaine in the last 30 days. The use of cocaine powder and crack cocaine varies widely between different groups and between cities. Nonetheless, multiple substance use is the predominating pattern of cocaine use, and the different routes of administration have to be taken into account