Nonlinear Nanomechanical Mass Spectrometry at the Single-Nanoparticle Level.

Nanoelectromechanical systems (NEMS) have emerged as a promising technology for performing the mass spectrometry of large biomolecules and nanoparticles. As nanoscale objects land on NEMS sensors one by one, they induce resolvable shifts in the resonance frequency of the sensor proportional to their weight. The operational regime of NEMS sensors is often limited by the onset of nonlinearity, beyond which the highly sensitive schemes based on frequency tracking by phase-locked loops cannot be readily used. Here, we develop a measurement architecture with which to operate at the nonlinear regime and measure frequency shifts induced by analytes in a rapid and sensitive manner. We used this architecture to individually characterize the mass of gold nanoparticles and verified the results by performing independent measurements of the same nanoparticles based on linear mass sensing. Once the feasibility of the technique is established, we have obtained the mass spectrum of a 20 nm gold nanoparticle sample by individually recording about 500 single-particle events using two modes working sequentially in the nonlinear regime. The technique obtained here can be used for thin nanomechanical structures that possess a limited dynamic range.

Building community resilience: business preparedness lessons in the case of Adapazari, Turkey.

The lack of attention paid to businesses in disaster management systems from the standpoint of state policies hampers efforts to build community resilience. This paper examines, therefore, the extent of business preparedness for disasters. Empirical research was conducted in Adapazari, Turkey, 13 years after the Izmit earthquake, which struck the northwest of the country on 17 August 1999, claiming the lives of some 17,000 people. For the study, 232 firms were selected to inquire about their preparedness before and after the event. It is hypothesised that business preparedness is influenced by the following set of variables: business size; business sector; business age; financial condition prior to the disaster; occupancy tenure; market range; education level; and previous disaster experience. In line with the findings of the research, a policy framework is constructed to rationalise the allocation of resources for building resilience at the aggregate level by facilitating business preparedness.

Comparison of retreatment ability of full-sequence reciprocating instrumentation and 360° rotary instrumentation.

OBJECTIVES: The purpose of the present study was to investigate the amount of root canal filling material after root canal filling removal with 360° rotary instrumentation or reciprocating motion with the same file sequence. MATERIALS AND METHODS: Root canals of the 36 mandibular premolars were shaped with ProTaper Universal instruments up to size F2 and filled with corresponding single gutta-percha cone and sealer. The teeth were assigned to two retreatment groups (n = 18): group 1 360° rotational motion and group 2 reciprocating motion of ATR Tecnika motors (1310° clockwise and 578° counterclockwise). Retreatment procedure was performed with ProTaper Universal retreatment files with a sequence of D1-3 and ProTaper Universal F3 instruments. Total time required to remove filling material were recorded. Remaining filling material was examined under stereomicroscope at ×8 magnification. The data were analysed statistically using the Mann-Whitney U test, and testing was performed at 95 % confidence level (p < 0.05). RESULTS: There were no significant differences between the groups (p > 0.05) in terms of remaining filling material. The total time required for retreatment was shorter in 360° rotational motion group compared to reciprocating motion group (p < 0.05). CONCLUSION: Both continuous rotation and reciprocating motion showed similar effectiveness in terms of root canal filling material removal. CLINICAL RELEVANCE: Using ProTaper Universal retreatment instruments with reciprocating motion of ATR motor and conventional rotary motion have similar efficacy in root canal filling removal.