Capillary tubes, X rays

Fig. 352. Comminution of sensitive alloys in the absence of air. ki, feg working chambers for handlii the alloy hi, high-vacuum stopcocks m capillary for x-ray sample u glass tube for armealit the alloy powder o electric furnace a adapter with the analysis and sample storage bulb f rotary milling tool.

The MCB tubes suit ideally into a concept of using glass capillary X-ray light guides to increase radiation intensity at the measurement spot. 

Figure 5.8 A Debye-Scherrer powder camera for X-ray diffraction. The camera (a) consists of a long strip of photographic film fitted inside a disk. The sample (usually contained within a quartz capillary tube) is mounted vertically at the center of the camera and rotated slowly around its vertical axis. X-rays enter from the left, are scattered by the sample, and the undeflected part of the beam exits at the right. After about 24 hours the film is removed (b), and, following development, shows the diffraction pattern as a series of pairs of dark lines, symmetric about the exit slit. The diffraction angle (20) is measured from the film, and used to calculate the d spacings of the crystal from Bragg s law.

For the X-ray scattering observations the samples were powdered and placed in Lindemann glass capillary tubes. The capillaries were held for 8 weeks at 293 K in closed containers in contact either with hexane vapour or with aqueous salt solutions of different relative humidity. At the end of the preparation, the capillary tubes were flame-sealed. X-ray measurements were made at the BM2 bending magnet beam line at the ESRF, Grenoble, France. With incident energy 18 keV, the wave vector range explored was 6x 10 [Pg.44]

X-Ray Powder Patterns. Samples for x-ray pattern determinations were sealed in 0.2-mm. glass capillary tubes under an atmosphere of argon. The samples were then exposed to nickel-filtered, CuKa radiation in an 11.459-cm. Debye-Scherrer camera for 18 to 20 hours. 

The preceding setup allows both X-ray diffraction (32) and absorption experiments (33, 34). The capillary geometry was used until about 30 years ago for ex situ XRD studies in connection with the placement of Lindemann tubes in powder Debye-Scherrer cameras. At that time, films were used to detect the diffracted X-rays. Today, this cumbersome technique has been almost completely replaced as modern detectors are used. 

X-ray diffraction experiments were performed on a STOE STADI-P diffractometer (CuKai radiation X = 1.5406 A) equipped with a linear position-sensitive detector. The solutions and the solids were introduced in a 0.3mm capillary Lindemann tube (Debye-Sherrer geometry). 

The next step is for a protein crystallographer to mount a small perfect crystal in a closed silica capillary tube and to use an X-ray camera to record diffraction patterns such as that in Fig. 3-20. These patterns indicate how perfectly the crystal is formed and how well it diffracts X-rays. The patterns are also used to calculate the dimensions of the unit cell and to assign the crystal to one of the seven crystal systems and one of the 65 enantiomorphic space groups. This provides important information about the relationship of one molecule to another within the unit cell of the crystal. The unit cell (Fig. 3-21) is a parallelopiped... 

Protein crystals, either sealed in capillary tubes with mother liquor or flash-frozen in a fiber loop, are mounted on the goniometer head, which is adjusted to center one face of the crystal perpendicular to the X-ray beam and to allow rotation of the crystal while maintaining centering. Flash-frozen crystals are held in a stream of cold nitrogen gas emerging from a reservoir of liquid nitrogen. 

The checker reports that the melting-point determination, run by inserting a capillary tube into a hot bath, gave a liquid at 170° which evolved a gas. X-ray diffraction data showed the absence of imidodiphosphoric acid tetramide, (NH2)2P(0)—NH—P(0)(NH,)s. f The University, Munich, Germany, t Monsanto Chemical Co., Dayton, Ohio. 

Figure 11.7 X-ray diffraction equipment in capillary configuration showing from left to right Cu x-ray tube, monochromator to select Cu K-alpha radiation, sample mounted in capillary tube, beam tunnel, and X celerator position sensitive detector. The tube and the detector are scanned through a range of angles (theta) by the goniometer (the device in the background on which they are both mounted), and the XRPD is recorded and stored on a computer for subsequent analysis and processing.

Aluminum iodide is dimeric in both the solid and gaseous states and in solution. The melting point of the product prepared as described above depends upon the technique employed. Samples contained in pyrex capillary tubes sealed with soft wax begin to decompose at 179° melting is complete and a meniscus is formed at 189.9° (corr.). In sealed capillaries, decomposition is first detectable at 178 to 179°, and melting is complete at 184° (corr.). Aluminum iodide is best characterized by its x-ray-diffraction pattern, which includes five quite distinct max-... 

A complex PMMA-based fluidic device was built by Soper s research group [68], which coupled capillary nanoreactors to microseparation platforms (electrophoresis chips) for the generation of sequencing ladders and PCR products. The nanoreactors consisted of fused silica capillary tubes with a few tens of nanoliters of reaction volume, which can be interfaced wiht the chips via connectors micromachined in PMMA, using deep X-ray etching. A DNA tem-... 

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