Optical observations

Perhaps the most significant complication in the interpretation of nanoscale adhesion and mechanical properties measurements is the fact that the contact sizes are below the optical limit ( 1 t,im). Macroscopic adhesion studies and mechanical property measurements often rely on optical observations of the contact, and many of the contact mechanics models are formulated around direct measurement of the contact area or radius as a function of experimentally controlled parameters, such as load or displacement. In studies of colloids, scanning electron microscopy (SEM) has been used to view particle/surface contact sizes from the side to measure contact radius [3]. However, such a configuration is not easily employed in AFM and nanoindentation studies, and undesirable surface interactions from charging or contamination may arise. For adhesion studies (e.g. Johnson-Kendall-Roberts (JKR) [4] and probe-tack tests [5,6]), the probe/sample contact area is monitored as a function of load or displacement. This allows evaluation of load/area or even stress/strain response [7] as well as comparison to and development of contact mechanics theories. Area measurements are also important in traditional indentation experiments, where hardness is determined by measuring the residual contact area of the deformation optically [8J. For micro- and nanoscale studies, the dimensions of both the contact and residual deformation (if any) are below the optical limit. 

For a radio astronomer, a star is a source of noise this noise can be detected and correlated from antenna to antenna in order to position precisely the source. For optical observer, the star is a source of photons, the unique photon goes through a variety of optical paths and materialize on the focal plane detector. 

In the case of optical observation of FCCs, film samples were put in a hot stage (Linkam, LK-600). Temperature was calibrated using standard materials. In and Sn Nitrogen gas was used at the rate of 50 ml/min. The number of isolated crystals near the center of the sample was counted. 

Time evolutions of Ix 0bs(< >t) of the mixture of PE with NA and that of PE without NA are shown in Figs. 7 and 8, respectively. They were observed at the same degree of supercooling AT as the optical observation shown in Fig. 6. The induction time observed by optical microscopy (ti(OM)) was... 

Figure 21.7 Comparison of mass spectra obtained from rat brain. Optical observation of microspotted tissue sections employing spray-droplet (a), droplet (b), and spraycoating (c) methods. Scale bar, 1.0 mm. White squares (a-c) represent the cortex (A, d) and the medulla (B, e) of the cerebellum region, respectively. Accumulated mass spectra collected from each region are shown (d, e). In each spectrum, asterisks represent major unique signals for spectra using the spray-droplet method. The number of detected signals in the mass range of 2000 < m/z < 30,000 from each region is shown (f). Reprinted with permission from Sugiura et al.7...

An interesting example of a DR for optical observations below 1K in strong magnetic fields is reported in ref. [35], A multistage nuclear demagnetization refrigerator is... 

The ejected material forms a cool molecular and dusty envelope which initially veils the star from optical observations as it goes through the stages of Mira variable followed by OH-infirared star or infrared carbon star later the star becomes hot enough to ionize part or all of the expanding gas-dust envelope forming a planetary nebula. 

Fig. 8.1. Ne/O ratio vs. O/H from (mainly optical) observations of H n regions in spiral and irregular galaxies and the Sun. Filled and open symbols represent results from different authors. After Garnett (2004).

The IRAS satellite mission, launched in 1983, provided a more complete survey of disk and active galaxies containing dust than had been possible from optical observations. Follow-up measurements of redshifts and other properties led to significant results for cosmology and the discovery of many luminous star-forming and active galaxies enshrouded by dust. A typical spiral galaxy like our own... 

C. Allain, D. Ausserre, and F. Rondelez, Direct optical observation of interfacial depletion layers in polymer solutions, Phys. Rev. Lett. 49, 1694-1697 (1982). 

In general, spectral regions III and IV are far away from the optical range for good insulators, while these regions can be optically observed for some semiconductors. This is the reason why many semiconductors, such as Ge and Si, have a metallic aspect, while most of the good insulators, such as KCl and NaCl, are highly transparent in the visible. 

However, as discussed below critical concentrations for cellulose, in a variety of solvents, and based on optical observations under crossed polars are much lower than predicted using eauation 1 and kw = 2 q. Como et al. (4 point out one has to consider the possibili that the lattice model does not accuratelv predict the values of V2 and that V2 values using the Onsager (28) and Isihara (30) theories are about half that predicted by equation 1. 

Rheo-Optical Observations. The rheo-optical observations were made with a WILD stereoscope equipped with a custom made rotary optical stage using polarized light. The rotary optical stage described in detail elsewhere (9) was used for both the steady state shear and dynamic test conditions. 

It has been shown that a metallic probe tip highly localizes and strongly amplifies the optical field throngh the resonance effect of the plasmon polaritons at the probe tip. This concept has made it possible to optically observe nanometric samples with a nanometric spatial resolntion. 

To the flat neck of the tube is attached (by means of picein) to the neck of tube, 2, (60 mm long), which is provided with the stopcock, 4, and two quartz windows, 3, for optical observation of nitrogen oxides density. After loading the tube, 1, with expl and assembling it together with tube,... 

The sightings of simultaneous, bunches of neutrinos in the KII [6] and IMB [7] detectors some three or four hours before optical observations of SN1987a is surely as good a demonstration of the existence of gravitational collapse supernovae as we can desire. The very short time between neutrinos and optical visibility is a surprise, speaking to the small size and unusual nature of the progenitor. We have performed [5] one of the many parallel analyses of these neutrinos [23-28]. 

The wave theory of light, which operates with continuous spatial functions, has worked well in the representation of purely optical phenomena and will probably never be replaced by another theory. It should be kept in mind, however, that the optical observations refer to time averages rather than instantaneous values. In spite of the complete experimental confirmation of the theory as applied to diffraction, reflection, refraction, dispersion, etc., it is still conceivable that the theory of light which operates with continuous spatial functions may lead to contradictions with experience when it is applied to the phenomena of emission and transformation of light. 

Precision of X-ray observations. X-rays do not penetrate the Earth s atmosphere and so all X-ray observations are performed from satellites (or balloons for hard X-rays). However, compared to optical observations, X-ray studies are not intrinsically limited by the number of cluster member galaxies. As an X-ray observation is made longer and longer, more and more X-ray photons are detected and measurements made from the observation can be made more and more precise (up to the systematic calibration of the detectors). 

Abstract Clusters are useful cosmological tools which allow to understand how large scale structures and galaxies evolve in the Universe. I will review some of the methods based on optical observations of clusters of galaxies to derive cosmological properties, describing methods and limitations to find clusters and to study these structures depending on cluster characteristics. 

In X-rays, detections of such distant structures are easier because they appear as extended sources and because the field is not providing such extended sources at these wavelengths in general. The contamination by field X-rays point sources is, however, sometimes very strong. Another problem is to measure the precise redshift of these extended sources at the same time. In any case, optical observations are needed to complete X-ray observations in order to confirm the nature of the source and to estimate its redshift. 

The optical chilled-mirror dew point technique is a fundamental measurement, because the saturation temperature determines the saturation partial pressure of the water vapor. A temperature element is then placed in thermal contact with the mirror, and the mirror temperature is utilized directly as the dew point or saturation temperature. The cooling of the mirror surface in the past was done by acetone and dry ice, liquid C02, mechanical refrigeration, and later by thermoelectric heat pumps. The thermoelectrically cooled, optically observed dew point hygrometer probe is illustrated in Figure 3.26. 

There are also brown dwarfs to consider. Brown dwarfs are astronomical objects somewhat between a planet and a star and have a mass less than 0.08 times the mass of our sun and a surface temperature below 2,500 K. (As comparison, the cool red dwarfs are about 3,000-3,400 K). A large number of brown dwarfs would not change how bright the Galaxy appears in optical observations but would change its total mass quite substantially. 

The pendant drop technique measures the shape of a liquid drop suspended from the tip of a capillary needle. The drop is optically observed and the surface tension is calculated from the shape of the drop. This method is not as precise as the force measurement method because it depends on the eye of the operator or the sophistication of detection hardware and analysis software. 

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