Macroscopic techniques

Jones C, Mulloy B, Thomas H. (eds.). Microscopy, Optical Spectroscopy and Macroscopic Techniques, Humana Press, Totowa, NJ, 1994. 

The distance scale associated within the glass transition is related to the method used. For example, thermal and mechanical techniques provide macroscopic views of the glass transition, whereas spectroscopy techniques yield a molecular-level view. Thus, it is not surprising to find that molecular-level techniques, such as NMR, may result in lower Tg values compared to those obtained using a macroscopic technique, such as DSC. Both Tg values are correct, but not necessarily equal, given the different points of view the two methods are probing. 

Thanks to the extensive literature on Aujj and the related smaller gold cluster compounds, plus some new results and reanalysis of older results to be presented here, it is now possible to paint a fairly consistent physical picture of the AU55 cluster system. To this end, the results of several microscopic techniques, such as Extended X-ray Absorption Fine Structure (EXAFS) [39,40,41], Mossbauer Effect Spectroscopy (MES) [24, 25, 42,43,44,45,46], Secondary Ion Mass Spectrometry (SIMS) [35, 36], Photoemission Spectroscopy (XPS and UPS) [47,48,49], nuclear magnetic resonance (NMR) [29, 50, 51], and electron spin resonance (ESR) [17, 52, 53, 54] will be combined with the results of several macroscopic techniques, such as Specific Heat (Cv) [25, 54, 55, 56,49], Differential Scanning Calorimetry (DSC) [57], Thermo-gravimetric Analysis (TGA) [58], UV-visible absorption spectroscopy [40, 57,17, 59, 60], AC and DC Electrical Conductivity [29,61,62, 63,30] and Magnetic Susceptibility [64, 53]. This is the first metal cluster system that has been subjected to such a comprehensive examination. 

Surface diffusion can be studied with a wide variety of methods using both macroscopic and microscopic techniques of great diversity.98 Basically three methods can be used. One measures the time dependence of the concentration profile of diffusing atoms, one the time correlation of the concentration fluctuations, or the fluctuations of the number of diffusion atoms within a specified area, and one the mean square displacement, or the second moment, of a diffusing atom. When macroscopic techniques are used to study surface diffusion, diffusion parameters are usually derived from the rate of change of the shape of a sharply structured microscopic object, or from the rate of advancement of a sharply defined boundary of an adsorption layer, produced either by using a shadowed deposition method or by fast pulsed-laser thermal desorption of an area covered with an adsorbed species. The derived diffusion parameters really describe the overall effect of many different atomic steps, such as the formation of adatoms from kink sites, ledge sites... 

By comparing the slopes of F-N-plots, as shown in Fig. 4.40(e), with and without adatoms on the surface, the dipole moments of adatoms are then derived. Table 4.7 lists some of the data obtained by different investigators. These values are in fair agreement with those obtained by other macroscopic techniques.201 One must recognize, however, that values obtained with macroscopic techniques are measured without the knowledge of whether these are single adatoms, or whether these adatoms have already been combined into clusters of different sizes, while some of them may in fact have been absorbed into lattice steps. FIM experiments have... 

Basic information needed to understand the physical and chemical properties of solid surfaces and thin solid films include the atomic structures and the compositional variations across the surface and interface layers. The atomic structures can be studied with microscopies and with surface sensitive diffraction and particle scattering techniques. Compositions of surfaces and thin films can be studied with the atom-probe FIM. In general, however, compositional analyses are mostly done with surface sensitive macroscopic techniques, such as auger electron... 

Sample surfaces prepared by various macroscopic techniques are not well characterized on an atomic scale over the extended area of the macroscopic surfaces. It is now well known that even the most carefully processed surfaces contain only domains of well defined atomic structures of sizes of the order of 100 to 1000 A. 

A. F. Drake, in Methods in molecular biology, Vol. 22 Microscopy, optical spectroscopy, and macroscopic techniques, C. Jones, B. Mulloy, and A. H. Thomas, eds. Humana Press, 173-182(1994). 

Poinar and colleagues (72) successfully extracted DNA from three human coprolites made by Native Americans in Hinds Cave, Texas more than 2,000 years ago. Not only were they able to extract human mtDNA from the coprolites, which were determined to belong to known Native American mitochondria] types, but they also were able to analyze DNA from the plants and animals eaten by these occupants of Hinds Cave. Importantly, they discovered that some of the species of plants and animals identified by molecular techniques were not detected in the same feces by macroscopic techniques (and some macroscopically identified species were not detected by the DNA analysis). The combination of the molecular and macroscopic evidence demonstrated that these three Native Americans had a diverse and well-balanced diet. 

Nanotechnology concerns itself with the very small, but in so far as it is now a technology it mostly sells macroscopic quantities of microscopically controlled structures, and must make these by macroscopic techniques. Some proclaimed preparations... 

Electrophoresis is a well known macroscopic technique which can also be applied in microstructures [11]. Forces can be quite high. A cell with a net imbalance of a thousand electronic charges in a field of 50 kV/m experiences a force of about 10"11 N. The heat that such fields and the resulting currents pro-... 

One of the macroscopic techniques for of establishing the transition has been developed by Platikanov and Rangelova [328,329]. It is based on measurement of the longitudinal specific electrical conductivity of a film obtained between two silver cylinders and the specific electrical conductivity of the initial solution as a function of temperature. The comparison of the results allows to find the temperature at which the CBF/NBF transition occurs. Fig. 3.67 plots these results. Line 1 characterising the temperature dependence of the longitudinal specific electrical conductivity Kf for CBF has the same slope as line 3 which refers to the temperature dependence of the specific electrical conductivity k of the bulk phase. The slope of line 2 which is for NBF is much steeper. The cross-point of lines 1 and 2 indicates the temperature of the CBF/NBF transition at the given electrolyte concentration in the initial solution. Here it is 31.6°C. 

The measurement of the decrease in foam column height induced by a-particle irradiation can be considered to belong to the macroscopic techniques. As shown in [325,330,331 ] the rate of foam destruction depends on the activity of the oc-source. 

Table 3.10 presents the values of Ce ,cr for some of the most employed surfactants determined by microscopic and macroscopic techniques. 

The Ceixr(r) dependence for microscopic films as well as the data about Cei.cr obtained by microscopic and macroscopic techniques reveal that the microscopic technique renders a possibility to study more precisely the concentration range close to Cei.cr values, i.e. the experiments can be performed within a region where the work for overcoming the disjoining... 

A large number of macroscopic properties of elastomer networks are closely related to the density of network junctions and the extent of their fluctuations. Qualitatively, any increase of network density causes an increase in stress, whereas fluctuations of network junctions leads to a decreasing stress. It is generally believed that a formation of additional network junctions resulting fi-om the presence of filler particles in the elastomer matrix is one of the reasons for the improvement of mechanical properties of filled elastomers. However, the application of macroscopic techniques does not provide reliable results for the network structure in filled elastomers. Furthermore, a lack of information exists on the dynamic behavior of adsorption junctions. The present study fills the gap of knowledge in this area. 

Adsorption and diffusion of alkanes in zeolites and in well-structured porous materials like MCM-41 materials are studied widely [1,5,8,9,11], The reported difusivities however differ sometimes by orders of magnitude. These differences are sometimes attributed to the use of microscopic techniques in stead of macroscopic techniques [12]. We, however, think that a major part of the found differences must be imputed to the use of a carrier gas. Adsorption is often studied in diluted systems with methods as ZLC [3], gaschromatography [4], inverse gas chromatography [10], gravimetry [12], > ile others are not using carriers gasses at all. 

This article shows that microscopy of ionomers is a powerful complementary technique to various spectroscopic and macroscopic techniques like EXAFS and rheology for the investigation of ionomers. If precautions are taken and data are carefully analyzed, microscopy can thus add valuable insights to results from other studies. Because of this, microscopy of ionomers is not only of interest for the scientist trying to imderstand the physics behind ionomer properties and behavior, but also for the engineer attempting to improve or adapt an existing or new ionomer for a desired application. 

Macroscopic techniques for assessing kinetically controlled reactions have typically been burdened by relatively slow data collection rates. Typically, these data collection rates range from tens of seconds to minutes. The two main types of macroscopic experiments use either batch or flow-through methods (Amacher, 1991 Sparks et al., 1996). 

Motion of the dispersed naththalene triplet probe in P-Np is evident at 180K. By analogy with previous observations of the PMMA system(]Q) such mobility might be concomitant with the onset of the g-relaxation. It is apparent from dynamic mechanical data at IHz that resolution of the a and g relaxations is difficult(M). it may be that the use of molecular probes and labels such as 1-VN (as described above) offers a more sensitive sensory exploration of the matrix than is afforded by macroscopic techniques. It is also possible that the degrees of freedom for motion imbued in the matrix do not result from the motion of ester groups as generally inferred in PMA and PMMA for the g-relaxation but that conformational changes within the it-butyl substituent itself, constitute sufficient release of free volume within the matrix to allow rotational mobility of both the 1-VN label and the dispersed naphthalene probe. 

Tracer diffusion is the classical macroscopic technique [204—208], and is regarded as... 

In performing TEM studies one should always be concerned with statistics, that is whether or not the specimen studied is representative for the sample as a whole. A zeolite crystal of 500 nm has a weight of about 10 13 gram in other words 1 gram of zeolite contains 1013 crystals. For this reason, conclusions from TEM in general or ET in particular should be carefully compared to results from macroscopic techniques such as XRD, XPS and physisorption that provide properties averaged over large samples. 

These quantitative data can underpin the results of macroscopic techniques as a first step. Moreover, it provides the microscopic basis for models to describe accessibility of porous materials. 

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