A tutorial on the validation of qualitative methods: From the univariate to the multivariate approach

This tutorial provides an overview of the validation of qualitative analytical methods, with particular focus on their main performance parameters, for both univariate and multivariate methods. We discuss specific parameters (sensitivity, specificity, false positive and false negative rates), global parameters (efficiency, Youden's index and likelihood ratio) and those parameters that have a quantitative connotation since they are usually associated to concentration values (decision limit, detection capability and unreliability region).     

Manipulation and behavior modeling of one-dimensional nanomaterials on a structured surface

Different diameters of multiwall carbon nanotubes (CNTs) are manipulated by a cantilever tip of an atomic force microscope (AFM) to investigate the motion properties of one-dimensional nanomaterials on a structured surface. To describe the mechanical behaviors of this kind of samples, two mechanical models based on continuum mechanics are proposed. Through foreseeable manipulation procedures, we are able to position the tubes onto pre-etched micro trenches, and then measure their Young's moduli by the three-point bending method. Both string-like and beam-like deformation forms are observed on the tested samples. Additionally, we present a reparable ‘collapse’ phenomenon of the nanotube bridges.     

A Wireless Sensor Network approach for distributed in-line chemical analysis of water

In this work we propose the implementation of a distributed system based on a Wireless Sensor Network for the control of a chemical analysis system for fresh water. This implementation is presented by describing the nodes that form the distributed system, the communication system by wireless networks, control strategies, and so on.Nitrate, ammonium, and chloride are measured in-line using appropriate ion selective electrodes (ISEs), the results obtained being compared with those provided by the corresponding reference methods. Recovery analyses with ISEs and standard methods, study of interferences, and evaluation of major sensor features have also been carried out.The communication among the nodes that form the distributed system is implemented by means of the utilization of proprietary wireless networks, and secondary data transmission services (GSM or GPRS) provided by a mobile telephone operator. The information is processed, integrated and stored in a control center. These data can be retrieved - through the Internet - so as to know the real-time system status and its evolution.     

Use of monoterpenes, 3-carene and 2-carene, as synthons in the stereoselective synthesis of 2,2-dimethyl-1,3-disubstituted cyclopropanes

The current review represents a systematic survey of the use of 2- and 3-carenes in the synthesis of chiral non-racemic organic compounds containing a 2,2-dimethyl-1,3-disubstituted cyclopropane fragment. The synthetic approaches to the cyclopropane derivatives are classified on the basis of the retention of their parent carane bicyclic skeleton in the final product or cleavage of the six-membered ring along the synthetic route.     

Large gate modulation in the current of a room temperature single molecule transistor

We have demonstrated a single molecule field effect transistor (FET) which consists of a redox molecule (perylene tetracarboxylic diimide) covalently bonded to a source and drain electrode and an electrochemical gate. By adjusting the gate voltage, the energy levels of empty molecular states are shifted to the Fermi level of the source and drain electrodes. This results in a nearly 3 orders of magnitude increase in the source-drain current, in the fashion of an n-type FET. The large current increase is attributed to an electron transport mediated by the lowest empty molecular energy level when it lines up with the Fermi level.