Microscopes and Sampling Techniques

Although many noble efforts at fabricating a microscope for infrared spectrometry using a prism monochromator were made during the 1940s and 1950s [5-10], and Perkin-Ehner actually advertised a microscope that could be installed in one of 

The condenser goes by two names some call it a Cassegrain, while others call it a Schwarzschild objective. The present author has always been rather confused about the difference between a Cassegrain and a Schwarzschild objective but, aiming to resolve such confusion, contacted one of the designers of the first FT-IR microscopes. Bob Messerschmidt (now with Rare Light, Inc.), as to their difference. His reply to this question was as follows  

The other two types of external reflection microspectroscopy are less well suited to the characterization of tissue samples. In the first type, which is variously called specular reflection, front-surface reflection or Kramers-Kronig reflection, the reflectance 

The final type of measurement that can be made with the microscope in its reflection mode is diffuse reflection (DR) spectroscopy. Today, very few appHca-tions of mid-lR microspectroscopy of neat samples are available, because for mid-IR DR spectrometry the samples should be diluted to a concentration of between 0.5 and 5% with a nonabsorbing diluent (e.g., KBr powder) to preclude band saturation and severe distortion by reflection from the front surface of the particles. However, this mode has substantial application for NIR measurements, where sample dilution is not needed. Because the absorption of NIR radiation by most samples is rather weak, they must either be at least 1 mm thick or be mounted on a reflective or diffusing substrate, such as a ceramic or Teflon disk. In the latter case, the spectrum is caused by a combination of diffuse reflection, transflection and front-surface reflection (hopefully with diffuse reflection being the dominant process). 

The other two types of external reflection microspectroscopy are less well suited to the characterization of tissue samples. In the first type, which is variously called specular reflection, front-surface reflection, or Kramers-Kronig reflection, the reflectance spectra of thick, nonscattering, bulk samples are measured and converted to the wavenumber-dependent optical constants, that is, the refractive index (v) and the absorption index k(v) by the Kramers-Kronig transform, as discussed by Griffiths and de Haseth [10]. As the requirement for thick nonscattering samples is essentially never met for tissue samples, this type of measurement is never used in medical diagnosis but has occasionally been used for the study of polymer blends. 

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Infrared microspectroscopy has been applied to the study of macerals (organic fractions) from a wide range of coals [106,116] and oxidized coal [117]. It may be performed either in transmission or reflection [106]. In the former case, sample preparation is tedious, and transmission IR microspectroscopy is seldom used. The preparation of samples for reflection measurements is simpler for example, the technique of attenuated total reflectance (ATR) has been applied to the study of coal [106]. Indeed, if the standard ATR accessories (which have been available for many years) were not suitable for block coal samples, recently, an ATR lens, equipped with a silicon (or germanium) internal reflection element, has become available for use with IR microscopes, and the technique was successfully applied... 

Melt-crystallized samples are semicrystalline with two components crystalline and amorphous. The natural density difference between the two phases is insufficient to give good contrast in the electron microscope and different techniques are used to enhance the density difference between the... 

Optical Techniques. The most important tool in a museum laboratory is the low power stereomicroscope. This instmment, usually used at magnifications of 3—50 x, has enough depth of field to be useful for the study of surface phenomena on many types of objects without the need for removal and preparation of a sample. The information thus obtained can relate to toohnarks and manufacturing techniques, wear patterns, the stmcture of corrosion, artificial patination techniques, the stmcture of paint layers, or previous restorations. Any art object coming into a museum laboratory is examined by this microscope (see Microscopy Surface and interface analysis). 

One of the most sensitive biological effects of ionizing radiation is to increase the frequency of normally observed chromosome aberrations (but not to induce qualitatively special abnormalities). Peripheral blood lymphocytes are the most feasible cells for chromosome investigations, as blood samples are easy to obtain and the techniques to stimulate the lymphocytes to proliferate within a culture medium and to prepare suitable chromosome slides for microscopic analyzation have their routine protocoil (e. g. Yunis, 1965 Lloyd et al, 1982). 

In order to prepare standard mineral mixtures, pyrite (Py), pyrrhotite (Po), chalcopyrite (Cp), sphalerite (Sp), siderite (Sid), dolomite (Dol), calcite (Cal) and quartz (Qz) were acquired as pure mineral samples through a specialized distributor (Minerobec, Canada). These 8 pure minerals were further cleaned under a binocular microscope and separately crushed to reach 95% under 150pm (typical tailings grain size distribution e.g. Aubertin et al. 2002). Each pure mineral powder was characterized thereafter with a series of chemical and mineralogical techniques. More details can be found in Bouzahzah et al. (2008). The relative density of each mineral specimen were measured with an He pycnometer and are... 

ATR FT-IR spectroscopy allows for analysis of the polymer surface, rather than the bulk of the sample. Whereas the spectra obtained from the FT-IR microscope and BCA are recorded in transmittance mode and are used to analyze the entire bead, an ATR objective can be brought into direct contact with the sample in order to yield information about the chemistry taking place mainly on the periphery of the bead. Some FT-IR microscopes are equipped with an ATR crystal, and ATR analysis can be achieved on a single bead [172], but there have been no reports of automated ATR instruments. This technique has been used in kinetic studies, to prove that the esterification of Wang resin (4) (Scheme 1.4) to give the corre-... 

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