Contactless

Active thermography is a contactless NDE technique that consists in the detection of infrared emission after the transient thermal excitation of the inspected structure. 

The weld depths penetration for gold-nickel alloy and tantalum cylinders have been well controlled by an entirely contactless ultrasound method. Nevertheless, the development of signal and image processing will allow to increase the resolution of the ultrasonic images. Moreover, in order to be able to size quite well the lacks of weld penetration, the simulation of the interaction beam-defect is presently developed in our laboratory. 

The performances of ultrasound generated and detected by lasers offer a wide field of applications in industry, so that we will pursue research for the testing of very small strucmres which could only be examined by a contactless technique. 

Contactless, nondestructive monitoring of band gaps in semiconductors Wide range of temperatures and ambients (air, ultrahigh vacuum) in-situ monitoring of semiconductor growth... 

In summary, CL can provide contactless and nondestructive analysis of a wide range of electronic properties of a variety of luminescent materials. Spatial resolution of less than 1 pm in the CL-SEM mode and detection limits of impurity concentrations down to 10 at/cm can be attained. CL depth profiling can be performed by varying the range of electron penetration that depends on the electron-beam energy the excitation depth can be varied from about 10 nm to several pm for electron-beam energies ranging between about 1 keV and 40 keV. 

For applied work, an optical characterization technique should be as simple, rapid, and informative as possible. Other valuable aspects are the ability to perform measurements in a contactless manner at (or even above) room temperature. Modulation Spectroscopy is one of the most usehil techniques for studying the optical proponents of the bulk (semiconductors or metals) and surface (semiconductors) of technologically important materials. It is relatively simple, inexpensive, compact, and easy to use. Although photoluminescence is the most widely used technique for characterizing bulk and thin-film semiconductors. Modulation Spectroscopy is gainii in popularity as new applications are found and the database is increased. There are about 100 laboratories (university, industry, and government) around the world that use Modulation Spectroscopy for semiconductor characterization. 

Commercial versions of PR are available. Other contactless methods of electro-modulation are Electron-Beam Electro-reflectance (EBER) and Contacdess Electroreflectance (CER). In EBER the pump beam of Figure 2 is replaced by a modulated low-energy electron beam (- 200 eV) chopped at about 1 kHz. However, the sample and electron gun must be placed in an ultrahigh vacuum chamber. Contactless electroreflectance uses a capacitor-like arrangement. 

In view of this apparent contradictory outcome from the transport and magnetic properties, we were motivated to investigate the dynamics of the charge excitation spectrum by optical methods. In fact, the optical measurement is a powerful contactless experimental tool which should in principle allow to unfold the disagreement between and p(7 since the optical response of a metal... 

By inspection windows and use of a pyrometer, visual inspection of the catalyst and temperature monitoring on-site in a contactless manner were performed. It turned out that a glowing, homogeneous texture occurs at catalyst temperatures between 900 and 1200 °C, GHSV values up to 10 h and pressures less than 1 MPa [3]. This is an indication of the absence of soot deposits. At lower temperatures or... 

Fig. 3.38 Natura hairdryer with contactless temperature sensor.

The main advantages of the simultaneous calibration of both sensors are the contactless measurements, so that no contamination with fluid can occur, and the possibility to calibrate fully assembled devices without the risk of decalibration due to subsequent assembly steps. 

Abstract Dye-doped polymeric micro- and nanobeads represent smart analytical tools that have become very popular recently. They enable noninvasive contactless sensing and imaging of various analytical parameters on a nanoscale and are also widely employed in composite sensing materials, in suspension arrays, and as labels. This contribution gives an overview of materials and techniques used for preparation of dye-doped polymeric beads. It also provides examples of bead materials and their applications for optical sensing and imaging. 

Borisov SM, Krause C, Arain S, Wolfbeis OS (2006) Simultaneous and contactless luminescent sensing and imaging of oxygen and carbon dioxide. Adv Mater 18 1511-1516... 

Organic modifiers have been frequently employed in CE to increase the solubility of hydrophobic solutes in the aqueous buffer system. Unfortunately, many organic modifiers are UV absorbent and cannot be used without considerable loss of sensitivity of detection. A contactless conductivity detection system has been developed which extends the application range of UV-absorbing solvents [ 119]. As both natural pigments and synthetic dyes absorb in the visible part of the spectra, the application of UV-absorbing organic modifiers in their CE analysis does not cause detection problems. 

J. Muzikar, T. van de Goor, B. Gas and E. Kenndler, Extension of the application range of UV-absorbing organic solvents in capillary electrophoresis by the use of a contactless conductivity detector. J. Chromatogr.A 924 (2001) 147-154. 

FIGURE 6 An electropherogram using detection by contactless conductivity of anions with an injection of 20 mbar for 5 s. Sample concentration (in order) 0.5 ppm bromide, chloride, nitrite, nitrate, sulfate, and fluoride and 1.0 ppm phosphate. Data courtesy of TraceDec. 

For systems with moderate-to-low probability, CE might not be the chromatographic quantification method of choice, and other alternatives, such as HPLC and GC, should be considered. However, specific procedures (e.g., off-line concentration, stacking techniques, extended light path capillaries) and detectors may be applied to increase solubility and sensitivity of detection, such as derivatization (e.g., carbohydrates, amino acids, amines, etc.) or the use of a specific detector (e.g., contactless conductivity detection, coupling with mass spectrometry, etc.). However, increasing the complexity of the methodology may be counterproductive if it leads to a lower robustness and transferability of the system. 

Two types of conductivity detectors exist the contact conductivity detector, where the electrodes are in direct contact with the electrolyte, and the contactless coupled conductivity detector (C D also called oscillometric detector). With this detector, two stainless-steel tubes that act as electrodes are mounted on a capillary at a certain distance from each other. By applying an oscillation frequency, a capacitive transition occurs between the actuator electrode and the liquid inside the capillary. After having passed the detection gap between the electrodes, a second capacitive transition between the electrolyte and the pickup electrode occurs (see Figures 7 and 8 which is an example of separation of cations). In different reviews, Zemann and Kuban and Hauser discuss the advantages of this technique which include rather simple mechanical parts and electronics, and Kuban et al. compared several C D detectors. This technique has also been used as a detector for analysis by microchip CE. C" D detectors are available to be mounted on existing CE instruments. 

FIGURE 7 Contactless coupled conductivity detection (C D) is based on two cylindrical metal electrodes, actuator, and pickup electrode, which are placed on the separation capillary. Schematically, it represents a series of a capacitor, an ohmic resistor, and a second capacitor (from Innovative Sensor Technologies GmbH). 

Zemann, A. J. (2003). Capacity coupled contactless conductivity detection In capillary electrophoresis. Electrophoresis 24, 2125—2137. 

Kuban, P., and Hauser, P. C. (2004). Contactless conductivity detection In capillary electrophoresis a review. Electroanalysis 16, 2009—2021. 

The contactless conductivity microchip detection system, developed in our laboratory [31], has been particularly useful for this task. Its popularity has grown rapidly in recent years. Conductivity is a universal detection technique for CE microchips, as it relies on the same property of the analyte as the separation itself, namely the mobility of ions under the influence of an electrical field. Such a detector can thus sense all ionic species having conductivity different from the background electrolyte. 

A dual electrochemical microchip detection system, based on the coupling of conductivity and amperometric detection schemes, was developed for simultaneous measurements of both nitroaromatic and ionic explosives [34], The microsystem relied on the combination of a contactless conductivity detector with an end-column thick-film carbon amperometric detector. Such ability to monitor both redox-active nitroaromatic and ionic explosives is demonstrated in Figure 13.7, which shows typical dual-detection electropherograms for a sample mixture containing the nitroaromatic explosives trinitrobenzene (TNB) (4), TNT (5), 2,4-DNB (6), and 2-Am-4,6-DNB (7), as well as the explosive-related ammonium... 

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