Columnar shaped microresonators for mass detection and gas analysis

In this paper miniaturized silicon columns mounted perpendicular to a surface are presented as microresonators for the detection of an exceedingly small mass. In a first sensor design the column resides on a rigid silicon substrate and is forced to oscillate in the first flexural eigenmode. Mass sensitivity was investigated loading a single latex sphere on the top surface of the column and detecting the frequency shift of the resonant frequency. Oscillation was monitored using the optical beam deflection method, focusing a laser beam at the same surface. However, optical readout was substantially hampered by scattering of the laser beam at the loaded particles and diffraction at the column surface. In a second optimized design a silicon column was mounted on a flexible silicon nitride membrane. In this way the optical readout was applied from the flip side of the membrane completely separating the load area and the optical beam path. A proof of principal is given for the optimized sensor design investigating the influence of pure gases on the extrinsic damping behavior of the membrane columnar oscillator.     

Automatic multi-partite graph generation from arbitrary data

In this paper we present a generic model for automatic generation of basic multi-partite graphs obtained from collections of arbitrary input data following user indications. The paper also presents GraphGen, a tool that implements this model. The input data is a collection of complex objects composed by a set or list of heterogeneous elements. Our tool provides a simple interface for the user to specify the types of nodes that are relevant for the application domain in each case. The nodes and the relationships between them are derived from the input data through the application of a set of derivation rules specified by the user. The resulting graph can be exported in the standard GraphML format so that it can be further processed with other graph management and mining systems. We end by giving some examples in real scenarios that show the usefulness of this model.     

Adsorption effect of a cationic surfactant at carbon paste electrode as a sensitive sensor for study and detection of folic acid

The present study is the first report on the effect of cetyltrimethylammonium bromide (CTAB) on the electrochemical behavior of folic acid (FA) at the surface of carbon paste electrode (CPE) in real samples. The studies were performed by cyclic voltammetry (CV), chronocoulometry and differential pulse voltammetry (DPV). CTAB, with a hydrophobic C–H chain, could absorb at the CPE surface by hydrophobic interaction and then changed the electrode/solution interface, and eventually affects the electrochemical response of FA, confirming from the remarkable oxidation peak current enhancement. For investigation of the electrode properties, CV technique was used at the various scan rates. Electrochemical parameters including diffusion coefficient (D), electron transfer coefficient (α) and ionic exchanging current density (j_o) were determined for the FA at the surface of the electrode. Under optimized conditions, the proposed method showed acceptable analytical performances for FA in terms of linearity (over the concentration range from 0.01 to 1.5 and 1.5 to 10.0 μM), detection limit (2.89 nM), repeatability (1.37%) and stability (13% reduction in peak current after 60 days). After studying on the effect of probable interferences it was found that the method was free of the interferences. Finally, the proposed method was successfully applied for the determination of FA in real samples.