Non-Gaussian Resistance Fluctuations in Gold-Nanoparticle-Based Gas Sensors: An Appraisal of Different Evaluation Techniques.

Volatile organic compounds, such as formaldehyde, can be used as biomarkers in human exhaled breath in order to non-invasively detect various diseases, and the same compounds are of much interest also in the context of environmental monitoring and protection. Here, we report on a recently-developed gas sensor, based on surface-functionalized gold nanoparticles, which is able to generate voltage noise with a distinctly non-Gaussian component upon exposure to formaldehyde with concentrations on the ppm level, whereas this component is absent, or at least much weaker, when the sensor is exposed to ethanol or to pure air. We survey four different statistical methods to elucidate a non-Gaussian component and assess their pros and cons with regard to efficient gas detection. Specifically, the non-Gaussian component was clearly exposed in analysis using level-crossing parameters, which require nothing but a modest computational effort and simple electronic circuitry, and analogous results could be reached through the bispectrum function, albeit with more intense computation. Useful information could be obtained also via the Lévy-stable distribution and, possibly, the second spectrum.

Lognormal distribution of firing time and rate from a single neuron?

Even a single neuron may be able to produce significant lognormal features in its firing statistics due to noise in the charging ion current. A mathematical scheme introduced in advanced nanotechnology is relevant for the analysis of this mechanism in the simplest case, the integrate-and-fire model with white noise in the charging ion current.

Electrical Maxwell demon and Szilard engine utilizing Johnson noise, measurement, logic and control.

We introduce a purely electrical version of Maxwell's demon which does not involve mechanically moving parts such as trapdoors, etc. It consists of a capacitor, resistors, amplifiers, logic circuitry and electronically controlled switches and uses thermal noise in resistors (Johnson noise) to pump heat. The only types of energy of importance in this demon are electrical energy and heat. We also demonstrate an entirely electrical version of Szilard's engine, i.e., an information-controlled device that can produce work by employing thermal fluctuations. The only moving part is a piston that executes work, and the engine has purely electronic controls and it is free of the major weakness of the original Szilard engine in not requiring removal and repositioning the piston at the end of the cycle. For both devices, the energy dissipation in the memory and other binary informatics components are insignificant compared to the exponentially large energy dissipation in the analog part responsible for creating new information by measurement and decision. This result contradicts the view that the energy dissipation in the memory during erasure is the most essential dissipation process in a demon. Nevertheless the dissipation in the memory and information processing parts is sufficient to secure the Second Law of Thermodynamics.

Material-specific thrombin generation following contact between metal surfaces and whole blood.

Little is known about the blood compatibility of metals used in various medical devices. We have previously shown that titanium and derivatives thereof are among the most thrombogenic materials which may explain its outstanding osteointegrating properties. The aim of the present study was to characterize the thrombogenic and complement-activating properties of various metals used today in medical applications. Polyester chips were coated with 50- to 100-nm thick layers of aluminium, iridium, indium, nickel, tantalum, tin, titanium, or zirconium using magnetron sputtering. The metal-coated chips were then incubated in direct contact with whole blood in an in vitro chamber model, and the blood was then analyzed for platelet counts, thrombin-antithrombin (AT), fXIIa-AT, fXIa-AT and fXIIa-C1INH complexes and the complement parameters C3a and sC5b-9. Titanium, tantalum and indium were found to exhibit pronounced thrombogenic properties, whereas aluminium, nickel and, in particular, iridium were essentially non-thrombogenic. Tin and zirconium were intermediate activators. All metals activated complement to a similar degree, with the exception of aluminium, which had more pronounced activating properties. This study clearly indicates that metals indeed have varying thrombogenic and complement activating properties. These studies have implications for the selection of metals intended for medical applications.