Transmission accessories

Forster et al. (1983) apparently used a simple quartz cuvette placed in a spectrometer without any further modifications similarly, Paze et al. (1999) referred to a quartz cell that was sealed after sample treatment and then inserted into the spectrometer. A design for transmission measurements was published by Melsheimer and Ziegler (1992), who referred to their device as a "scattered transmission accessory." The photomultiplier is placed only 28 mm behind the sample attenuators of 1.7 or 10% were used in the reference beam. 

An interesting variant of the spectroscopic experiment is in situ investigations under catalytic conditions. For this purpose a special reactor cell has been designed equipped with quartz windows which allows the monitoring of the course of the reaction on the catalyst wafer. As an example, the transformation of ethene over HZSM-5 was studied up to 573 K using a scattered transmission accessory in which the sample is placed directly in front of the multiplier, so that the forward-scattered light almost completely impinges the detector [130]. At lower temperatures no substantial differences could be established between the carbocation spectra obtained in situ and ex situ. The spectroscopic discrepancies in the peak positions above 548 K are tentatively explained by the different... 

Figure 4.22. Optical scheme of diffuse-transmission accessory with side iiiumination of powder sampie (1) sampie (2,3) directing and focusing mirrors, respectively. Reprinted, by permission, from V. P. Toistoy, Methods of UV-Vis and IR Spectroscopy of Nanolayers, St. Petersburg University Press, St. Petersburg, 1998, p. 155, Fig. 4.25. Copyright 1998 St. Petersburg University Press.

In reflectance sampling it takes extra mirrors to focus the light onto the sample and to collect the reflected light. These extra mirrors are contained in reflectance accessories that either mount on the base plate in the FTIR sample compartment or slide into the sample slide mount. These accessories must be custom built for the make and model of FTIR in which they are going to be used. A problem with reflectance accessories is that they are thousands of dollars more expensive than transmission accessories. There are several companies that make customized FTIR reflectance accessories, and they can be found via an Internet search. 

The many options available for lift trucks f l into two classes vehicle specialties, which include controls, transmissions, guards, etc. and accessories, which are devices that handle specific types of loads (Fig. 21-55). Included in this second category are high-lift masts, up to 7 m (24 ft) handhng attachments for circular products, such as drums and roll goods attachments such as carton clamps and the fork side-to-side shifting mechanism. 

In a previous section we mentioned the significance of myosin filament structure. In nematodes two forms of myosin-II, myosin A and B, are required for proper filament stmcture (Epstein, 1988). The two forms of myosin are expressed at the proper time to allow for correct filament assembly. An accessory protein called paramyosin is also required for correct filament assembly. In vertebrate cardiac muscle, there are also two isoforms of myosin-II a-myosin and p-myosin. The proper ratio of these two proteins is of utmost importance for proper muscle activity. The incorrect synthesis of a- and P-myosins results in a severe cardiac disorder known as hypertrophic cardiomyopathy. Genetic transmission of the disease occurs in about 55% of families. The inherited condition is called familial hypertrophic cardiomyopathy (FHC), and this condition is a leading cause of sudden death in young athletes. 

Li C.S., Kaba H., Saito H. and Seto K. (1992b). Estrogen infusions into the amygdala potentiate excitatory transmission from the accessory olfactory bulb to tuberoinfundibular arcuate neurons in the mouse. Neurosci Lett 143, 48-50. 

Transmission electron microscopy pictures were taken using a JE0L 100 CX microscope. For some samples lateral micro-analysis of thin sections of zeolite was carried out using a HB-5 VG microscope equipped with EDX accessory at IFP (11). 

All of the usual sampling techniques used in infrared spectroscopy can be used with FT-IR instrumentation. The optics of the sampling chamber of commercial FT-IR instruments are the same as the traditional dispersive instruments so the accessories can be used without modification for the most part. To make full use of the larger aperature of the FT-IR instrument, some accessories should be modified to accomodate the larger beam. The instrumental advantages of FT-IR allow one to use a number of sampling techniques which are not effective using dispersive instrumentation. Transmission, diffuse reflectance and internal reflectance techniques are most often used in the study of epoxy resins. 

Because, to date, no IRS accessories have been designed to benefit from the larger beam diameter of FT-IR, the spectral improvement achieved with FT-IR IRS is not as great as observed with FT-IR transmission compared to dispersive instruments. However, the signal averaging capability and speed make FT-IR a very useful tool. 

FTIR Microspectroscopy.3 A microscope accessory coupled to a liquid-nitrogen-cooled mercury-cadmium-telluride (MCT) detector can be used to obtain an IR spectrum. This is possible in both the transmission and reflectance modes. Several beads are spread on an IR-transparent window (NaCl, KBr, diamond) and possibly flattened via a hand-press or a compression cell. The IR beam is focused on a single bead using the view mode of the microscope. The blank area surrounding the bead is isolated using an adjustable aperture, and a spectrum is recorded using 32 scans (<1 min). A nearby blank area of the same size on the IR transparent window is recorded as the background. 

Figure 10.21—Optical path of the 1R beam in an 1R microscope). The sample can be examined in transmission or in reflection mode. This accessory can be installed on a spectrometer that has a deflected beam.

Bruker has introduced an FT-Raman microscope which is an accessory to an FT-IR spectrometer (42). The coupling between the microscope and the Raman module is made by NIR-fiber optics. In the wavelength range of the Raman experiment excited by a Nd YAG laser, the fiber optics transmission is at a maximum, thus allowing the experiment to be successful (43). Spatial resolution down to 5//m can be achieved. The technique appears to be a capable adjunct to FT-IR microscopy. 

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