Static-mode technique

The DMA can be operated in a dynamic or static mode. In the dynamic mode, a probe with an oscillating frequency enables the entire photoinduced polymerization to be followed with real-time monitoring of shrinkage, sample viscosity, and modulus. Alternatively, if it is operated in a static mode, the DMA essentially becomes a TMA. The dynamic-mode DMA measurements are possible but difficult to carry out since the probe must essentially float on the initially uncured liquid and hence, is not discussed here. Instead, TMA-like measurements in a static mode are described, as illustrated in Rg. 4.32. Bair et al. (1998,2000). This static-mode technique can be applied to samples with a wide range of shrinkages, from <0.1% to >10%. The detection limit for sample shrinkage in 500-pm-thick specimens using this static DMA method is... 

SALI compares fiivorably with other major surface analytical techniques in terms of sensitivity and spatial resolution. Its major advantj e is the combination of analytical versatility, ease of quantification, and sensitivity. Table 1 compares the analytical characteristics of SALI to four major surfiice spectroscopic techniques.These techniques can also be categorized by the chemical information they provide. Both SALI and SIMS (static mode only) can provide molecular fingerprint information via mass spectra that give mass peaks corresponding to structural units of the molecule, while XPS provides only short-range chemical information. XPS and static SIMS are often used to complement each other since XPS chemical speciation information is semiquantitative however, SALI molecular information can potentially be quantified direedy without correlation with another surface spectroscopic technique. AES and Rutherford Backscattering (RBS) provide primarily elemental information, and therefore yield litde structural informadon. The common detection limit refers to the sensitivity for nearly all elements that these techniques enjoy. 

TOF-SIMS was pioneered by Professor Benninghoven and his group in the early 1980s [109], originally developed in static mode and applied for the chemical analysis (elemental as well as molecular) of the uppermost monolayer of solid surfaces [110]. By the introduction and further development of the dual beam technique, the TOF-SIMS can... 

Static pressurized hot solvent extraction (SPHSE), which shall henceforward be referred to as accelerated solvent extraction (ASE) for the reasons stated above, is the less flexible PHSE mode in terms of alteration or coupling to other techniques but is so far the more widely used — in fact, it accounts for over 65% of the PHSE publications reported since 1994. This is mainly the result of the sole commercially available extractor (the Dionex 200 model) implementing the static mode alone and also of the large number of studies conducted by different or even the same authors on the same analytes in the same matrices, which have therefore contributed little or nothing new in this area [58-63]. 

The evaluation of the commercial potential of ceramic porous membranes requires improved characterization of the membrane microstructure and a better understanding of the relationship between the microstructural characteristics of the membranes and the mechanisms of separation. To this end, a combination of characterization techniques should be used to obtain the best possible assessment of the pore structure and provide an input for the development of reliable models predicting the optimum conditions for maximum permeability and selectivity. The most established methods of obtaining structural information are based on the interaction of the porous material with fluids, in the static mode (vapor sorption, mercury penetration) or the dynamic mode (fluid flow measurements through the porous membrane). 

The type of information provided by the techniques listed in the tables also varies greatly. Many spectroscopic techniques give qualitative and/or quantitative elemental composition. The vibrational techniques, however, generally provide information on the molecular structure. SIMS, especially in the static mode (SSIMS or TOFSIMS), can yield information on molecular structures and even orientation of monolayers [5-10]. This is particularly useful for the study of the absorption of coupling agents on metals or to determine the effects of plasma treatments on polymer surfaces [11]. TOFSIMS instruments also have capabilities for determining the two-dimensional distributions of elements or molecular species at the surface, similar to the capabilities (for elements only) offered by AES and EDXA or WDXA. 

In the contact mode, there are static modes (de-modes), and dynamic modes (ac-modes). In the former, a cantilever-type spring bends in response to the force which acts on the probing tip until a static equilibrium is established [1]. In the dynamic mode, the lever oscillates close to its resonance frequency. A distance-dependence force shifts the resonance curve. Another technique is to modulate the position of the sample at a frequency below the cantilever resonance but above the feedback-response frequency and send the response signal to a lock-in amplifier to measure the signal s amplitude and phase [4]. The lock-in output is connected to the auxiliary data acquisition channels to form an image - this approach is popularly known as force modulation (FM-mode). FM-mode imaging or force cmve is an AFM technique that identifies and maps differences in surface stiffness or elasticity. 

Neither MAE nor ASE is currently in a configuration that would readily lead to the automation of sample preparation. Supercritical fluid extraction can be used as online system that can then be connected to the chromatographic and detection systems. Connected online with the GC/MS, SFE was successfully used for the determination of PAHs in marine sediments. Using either CO2 alone or modified with toluene or MeOH in the extraction, the PAHs were cryofocused in the accumulation cell of the GC and then directly chromatographed. For the study of PAHs in marine sediments, a new extraction technique, which consists of the combination of ASE (dynamic and static mode) and SFE (dynamic mode), was developed, with an extraction time longer than in ASE but shorter than in SFE, and... 

The MC-ICP-MS measurements were performed at a power of about 1200 W, which correspond to so-called hot plasma conditions. The stable introduction system (SIS) used consists of a quartz dual-spray chamber with a low-flow perfluoroalkoxy (PFA) microconcentric nebulizer, which produces a flow rate of approximately 50 pL/min. A conventional H cone system was used. Typically, a ° Pb signal of 4 V per 100 ng/mL is obtained with Faraday cup detectors (10 fl). The instrument is located in a clean laboratory (ISO 7, NF ISO 14644-1). The T1 spike technique, which allows in-run instrumental bias correction, was used. The required set of Faraday cups simultaneously collects the following masses Hg or Hg, Tl, Pb -h Hg, =T1, ° Pb, Pb, and Pb (Thble 31.1). A gain calibration of all the Faraday cups was carried out to determine the correction coefficients between all the Faraday cups, after the most efficient instrumental settings were determined by using a pure Pb standard solution (SRM-981) at 50 n mL. Then, the peak shape at all masses of interest was evaluated. For a given analysis, 5 blocks of 10 cycles with 8-s integration time per peak were recorded in static mode for common samples over 7 min [9]. 

A practical definition could finally also be derived from the capabilities of the instrumentation in use. For instance, SIMS, the most widespread MS technique, applied to surface and thin films can be operated in static mode (giving information from the first atomic layers of a nearly undamaged surface) or dynamic mode (depth profile of the layer). When the material to be analyzed is sputtered, this sputtering could be very slow, providing a practical limit (often in the micrometer range for SIMS) to the thickness range achievable in a reasonable amount of time. 

The use of tomography in a static mode allows the recovery of the 3D structure of a membrane. In the membrane field, the size of the observed objects (for example pores or particles) is often in a range that covers from microns to nanometers. Taking into account that the lowest resolution (up to now) is 0.28 pm for an object size of 600 pm in the ID 19 line at ESRF [10], objects in the micron range could only be observed inside a small sample (one membrane). As rotation of the sample is needed, membranes with a rotation axis are preferred even if new techniques like synchrotron radiation computed laminography [13] allows the observation of flat samples. SRpCT enables complete visualization of a cross-section of the membrane without preparation. So a wetted membrane can be observed with the fluids that are used in the membrane process (water, bubble, etc.). In the case of hollow fibers, it is not necessary to cut the membrane because the axis of the fiber could be used as the axis of rotation. So X-ray tomography is a good tool to observe hollow fibers. 

To reduce the large number of elastic coordinates, a standard component mode technique is utilized [11]. This approach involves using a relatively small number of shape functions for each elastic body. The shape functions used consist of selected vibration modes, all constraint modes, and any necessary static correction modes. The important issue of how these modes are best selected is a area much on going work in the multibody dynamics community and will not be addressed here. 

The calorimetric techniques for measuring heats of mixing two fluids can be classified into their mode of measurement and their principle of heat detection. The isothermal displacement calorimetry will refer to a static mode and flow calorimetry, to a dynamic mode . The principles of heat detection in the following examples will be power compensation or heat flux determination. 

Batts and Paul [101b] used time-of-flight secondary-ion mass spectrometry (ToF-SIMS) to investigate the competitive adsorption of a cationic fluorinated surfactant (FC-134) at the gelatin-air interface. ToF-SIMS is a very sensitive surface analysis technique. In the static mode, the sampling depth of ToF-SIMS is only one to two monolayers. However, the ToF-SIMS data are difficult to interpret in quantitative terms and experimental conditions must be carefully controlled. Batts and Paul used positive secondary-ion spectra only, although negative-ion spectra may have been used as well. 

Electrochemical cells may be used in either active or passive modes, depending on whether or not a signal, typically a current or voltage, must be actively appHed to the cell in order to evoke an analytically usehil response. Electroanalytical techniques have also been divided into two broad categories, static and dynamic, depending on whether or not current dows in the external circuit (1). In the static case, the system is assumed to be at equilibrium. The term dynamic indicates that the system has been disturbed and is not at equilibrium when the measurement is made. These definitions are often inappropriate because active measurements can be made that hardly disturb the system and passive measurements can be made on systems that are far from equilibrium. The terms static and dynamic also imply some sort of artificial time constraints on the measurement. Active and passive are terms that nonelectrochemists seem to understand more readily than static and dynamic. 

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