Suitability of carbon nanotubes grown by chemical vapor deposition for electrical devices

Using carbon nanotubes (CNTs) produced by chemical vapor deposition, we have explored different strategies for the preparation of carbon nanotube devices suited for electrical and mechanical measurements. Though the target device is a single small diameter CNT, there is compelling evidence for bundling, both for CNTs grown over structured slits and on rigid supports. Whereas the bundling is substantial in the former case, individual single-wall CNTs (SWNTs) can be found in the latter. Our evidence stems from mechanical and electrical measurements on contacted tubes. Furthermore, we report on the fabrication of low-ohmic contacts to SWNTs. We compare Au, Ti and Pd contacts and find that Pd yields the best results.Comment: pdf including figures, see: http://www.unibas.ch/phys-meso/Research/Papers/2004/Suitability-CVD-tubes.pd

MACHINE LEARNING TOOLS IN THE ANALYZE OF A BIKE SHARING SYSTEM

Advanced models, based on artificial intelligence and machine learning, are used here to analyze a bike-sharing system. The specific target was to predict the number of rented bikes in the Nova Mesto (Slovenia) public bike share scheme. For this purpose, the topological properties of the transport network were determined and related to the weather conditions. Pajek software was used and the system behavior during a 30-week period was investigated. Open questions were, for instance: how many bikes are shared in different weather conditions? How the network topology impacts the bike sharing system? By providing a reasonable answer to these and similar questions, several accurate ways of modeling the bike sharing system which account for both topological properties and weather conditions, were developed and used for its optimization

Probability density functions of work and heat near the stochastic resonance of a colloidal particle

We study experimentally and theoretically the probability density functions of the injected and dissipated energy in a system of a colloidal particle trapped in a double well potential periodically modulated by an external perturbation. The work done by the external force and the dissipated energy are measured close to the stochastic resonance where the injected power is maximum. We show a good agreement between the probability density functions exactly computed from a Langevin dynamics and the measured ones. The probability density function of the work done on the particle satisfies the fluctuation theorem

Antibiotics Residues as Limiting Factor of Honey Quality

Residues of veterinary drugs represent a significant risk to the health of honey consumers. Antibiotics can get into honey by using the antibiotics for treatment and prevention of bees diseases but also through the plant nectar and pollen. In Serbia, the use of antibiotics in beekeeping for bacterial diseases treatment is prohibited and accordingly there is no prescribed maximum permissible concentration for them in honey. The aim of this paper is to monitor the presence of antibiotic residues in honey which necessarily indicate their illegal and uncontrolled use. The presence of antibiotic residues in honey was screened for microbiological method "Modified method 4 plates" (EUR 15127-EN). The total of 135 samples of different honey types has been examined. Five of them (3.7%) were positive to antibiotic residues. The presence of antibiotic residues was found in the acacia honey (0.31%), linden honey (0.33%), sunflower honey (0.19%), mixed honey (0.17%) and honeydew honey (0.10%). Such unprofessional, unconscionable and unlawful use of antibiotics leads to their presence in honey and other bee products, as well as in the highly desirable and valuable products making them unusable

Superconducting and Normal State Properties of Neutron Irradiated MgB2

We have performed a systematic study of the evolution of the superconducting and normal state properties of neutron irradiated MgB$_2$ wire segments as a function of fluence and post exposure annealing temperature and time. All fluences used suppressed the transition temperature, Tc, below 5 K and expanded the unit cell. For each annealing temperature Tc recovers with annealing time and the upper critical field, Hc2(T=0), approximately scales with Tc. By judicious choice of fluence, annealing temperature and time, the Tc of damaged MgB2 can be tuned to virtually any value between 5 and 39 K. For higher annealing temperatures and longer annealing times the recovery of Tc tends to coincide with a decrease in the normal state resistivity and a systematic recovery of the lattice parameters.Comment: Updated version, to appear in Phys. Rev.