Numerical analysis of sound radiation from rotating discs

The analysis of sound radiation from rotating elastic discs, e.g. saw blades, is an interesting research topic. Especially for people who work in the vicinity of such machines, health related issues with respect to noise exposure levels gain more and more awareness. Therefore, the industry is faced with the challenge of developing quieter products in order to improve the working environment and to extend the time a worker can use these tools before a harmful situation arises. Moreover, less noise emission means less energy consumption and therefore a higher productivity. In this paper, the authors investigate the sound radiation from a rotating disc where the sound power is used as a global measure for the acoustic performance. Different methods for calculating the sound power of a spinning saw blade are compared. These are a fully coupled finite element approach, a hybrid finite element/boundary element approach, a simplified form of the Rayleigh integral known as the lumped parameter model, and the equivalent radiated sound power. The results show good agreement between the costly full models and those utilizing approximation methods which can save remarkable computational costs. The proposed frame can be used in optimization procedures for developing quieter saw blades and other rotating discs. Furthermore, the paper discusses mode splitting which is a well-known phenomenon for rotating machinery. For this, the results of sound radiation are investigated with respect to the question whether mode splitting is actually audible

Failure of an Automated Blood Culture System To Detect Nonfermentative Gram-Negative Bacteria

During a 1-year study we observed that both aerobic and anaerobic blood culture bottles from patients were negative by the BacT/Alert system during a 7-day incubation period. However, upon subcultivation of negative bottles, growth of Pseudomonas aeruginosa was detectable. In an attempt to explain this observation, aerobic BacT/Alert Fan bottles were seeded with a defined inoculum (0.5 McFarland standard; 1 ml) of Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, P. aeruginosa, Stenotrophomonas maltophilia, or Acinetobacter baumannii. Half of the inoculated bottles were loaded into the BacT/Alert system immediately, and the remainder were preincubated for 4, 8, 16, and 24 h at 36°C. With preincubation all bottles seeded with the Enterobacteriaceae signaled positive during the next 1.5 h. Organisms in bottles seeded with the nonfermentative species P. aeruginosa and A. baumannii remained undetected by the BacT/Alert system for 7 days. S. maltophilia was detected if the preincubation time was equal or less than 8 h. Without preincubation all bottles seeded with the Enterobacteriaceae or nonfermentative species signaled positive. Since nonfermentative species seem to enter a state of bacteriostasis within the preincubation period, we reasoned that an unknown factor is consumed. Accordingly, a smaller inoculum should allow the detection of nonfermentative species, even after preincubation, and serial dilutions of P. aeruginosa were detected in preincubated bottles. In this case preincubated bottles signaled positive faster than bottles without preincubation. We conclude that all bottles from clinical settings should be subcultured prior to loading to avoid false negatives. An alternative may be preincubation at room temperature

Poly(fluorenevinylene) derivative by Gilch polymerization for light-emitting diode applications

The synthesis of poly(9,9-di-n-octylfluorene-2,7-vinylene) (PFV) via Gilch polymerization together with its characterization and purification using membrane technology was reported. The purity and structure of the monomer were confirmed by 1H NMR , 13C NMR, and elemental analyses. The key factor for obtaining the high molecular weight of the PFV was the introduction of a chloromethyl group into the 9,9-di-n-octylfluorene unit. The optical absorption (Abs) and photoluminescence (PL) spectra of the thin PFV film were obtained.close1039

Synthesis of Polyfluorenes with Pendant Silylcarboranes

The synthesis of a novel silylcarborane-containing fluorene monomer is reported in the present paper. Homo- and copolymerization via microwave-assisted Ni(0)-medialed coupling are described, and the influence of sterically crowded silylcarboranes on the polymerization outcome is assessed. The fluorescence spectra and thermal characteristics of the resulting polymers are analyzed and compared to determine the impact of carborane cages. Pendant carboranes are shown to improve the stability of annealed thin films. and potential implications in sensing devices and neutron detection are discussed