Spontaneous mechanical oscillation of a DC driven single crystal

There is a large interest to decrease the size of mechanical oscillators since this can lead to miniaturization of timing and frequency referencing devices, but also because of the potential of small mechanical oscillators as extremely sensitive sensors. Here we show that a single crystal silicon resonator structure spontaneously starts to oscillate when driven by a constant direct current (DC). The mechanical oscillation is sustained by an electrothermomechanical feedback effect in a nanobeam, which operates as a mechanical displacement amplifier. The displacement of the resonator mass is amplified, because it modulates the resistive heating power in the nanobeam via the piezoresistive effect, which results in a temperature variation that causes a thermal expansion feedback-force from the nanobeam on the resonator mass. This self-amplification effect can occur in almost any conducting material, but is particularly effective when the current density and mechanical stress are concentrated in beams of nano-scale dimensions

Summary of the FESAC Transformative Enabling Capabilities Panel Report

The U.S. Fusion Energy Sciences Advisory Committee was charged “to identify the most promising transformative enabling capabilities (TEC) for the U.S. to pursue that could promote efficient advance toward fusion energy, building on burning plasma science and technology.” A subcommittee of U.S. technical experts was formed and received community input in the form of white papers and presentations on the charge questions. The subcommittee identified four “most promising transformative enabling capabilities”: 1. advanced algorithms 2. high critical temperature superconductors 3. advanced materials and manufacturing 4. novel technologies for tritium fuel cycle control. In addition, one second-tier TEC, defined as a “promising transformative enabling capability,” was identified: fast-flowing liquid-metal plasma-facing components. Each of these TECs presents a tremendous opportunity to accelerate fusion science and technology toward power production. Dedicated investment in these TECs for fusion systems is needed to capitalize on the rapid advances being made for a variety of nonfusion applications to fully realize their transformative potential for fusion energy

Colonoscopy practice in Italy: a prospective survey on behalf of the Italian Association of Hospital Gastroenterologists

BACKGROUND: Examining the current practice is important for the benchmarking of quality of colonoscopy and the comparison with the standards and recommendations expected by professional societies. AIM: To describe colonoscopy practice in Italy, on the basis of prospective analysis of a large number of examinations performed by operators with different levels of expertise in a wide range of unselected centres. DESIGN AND SETTING: Cross-sectional, prospective and multicentre study. METHODS: The main features of each endoscopy centre (structure indicators) were collected through the use of a standardised questionnaire. A second questionnaire was used to prospectively record details of all the consecutive colonoscopies performed in a 2-week study period. RESULTS: Data from 278 centres and 12,835 consecutive colonoscopies were evaluated. Centres were uniformly distributed throughout Italy - north, centre and south - as was their organizational complexity and workload. Overall, adequate facilities (i.e. cleaning area for disinfection/reprocessing, equipped recovery room), and safety equipment (i.e. pulse oximetry, equipment for emergency cardiopulmonary resuscitation) were lacking in a considerable amount of centres, especially in those with a lower degree of organizational complexity. Written informed consent was routinely required in 87% of the centres, but a specific consent for colonoscopy, including detailed information on adverse events, was adopted by 66%. Regular programs for recording some quality indicators (i.e. cecal intubation, quality of bowel cleansing, patients' satisfaction and complications) were implemented in a minority of centres. About 93% of the colonoscopies were performed for diagnostic purpose; screening and surveillance accounted for 13.7% and 25.3% of the indications, respectively. Sedation and/or analgesia was administered in about half of the patients. Overall, colonoscopies were completed to the cecum in 80.7% of cases, and only 22.1% of the centres reported a cecal intubation rate >or=90%; this figure was reported in 33.1% of centres with high-organizational complexity and in 14.4% of outpatient units. The overall incidence of immediate complications was low (2 perforations, 26 bleedings and 32 serious cardiorespiratory complications). CONCLUSIONS: This study documented a wide variation in colonoscopy practice between centres and highlighted problem areas where interventions are needed to improve performance and safety of the examinations