X-ray sensitive

Thus it can be seen that X-ray sensitivity for a positive resist... 

Sinclair WK, Morton RA. X-ray sensitivity during the cell generation cycle of cultured Chinese hamster cells. Radiat Res 1966 29(3) 450 174. 

C/cm2 plotted against the Mo soft x-ray sensitivity in mJ/cm2 of incident x-ray flux. The unit slope of the plot suggests that the basic radiation chemistry is the same in both cases. 

Sankaranarayanan. K., Ferro, W. Zijlstra. J.A. (1983) Studies on mutagen-sensitive strains of Drosophila melanogaster III. A comparison of the mutagenic sensitivities of the ebony (UV and X-ray sensitive) and Canton-S (wild-type) strains to MMS, ENU, DEB, DEN and 2,4,6-CL3-PDMT. Mutat. Res., 110, 59-70... 

In the direct method, an X-ray-sensitive vidienn TV camera direedy converts the X-ray image into an electronic charge pattern on a photoconductive target, which is read out by a scanning electron beam and displayed visually on a TV monitor. 

The simplest X-ray detector, and for years the workhorse of detectors, is X-ray-sensitive film, but film has been almost completely replaced by image plates and CCD detectors, which are described in more detail later. Various types of cameras (next section) can direct reflections to detectors in useful arrangements, allowing precise determination of indices and intensities for thousands of reflections from a single image. 

Figure 4. Postulated schematic showing the mechanism for the metabolic effects of MGd under X-ray sensitization conditions.

As noted above, the X-ray sensitization of cells using MGd has been investigated extensively and appears to operate at least in part in an oxygen dependent manner, with cytotoxic activity that is substantially enhanced upon the addition of ascorbate to the media [69], The cytotoxic activity of MGd can also be enhanced with L-buthionine-S,R-sulfoximine (BSO), an irreversible inhibitor of an enzyme involved in glutathione biosynthesis (y-glutamylcysteine synthetase), that serves to suppress the synthesis of ROS-protective glutathione. Presumably, this activity is responsible for the in vitro radiation enhancing effect of BSO [66,71],... 

Second, the use of meshed particles versus a pressed wafer will typically lead to nonuniformity of X-ray absorption thickness. This can be directly observed by placing an X-ray sensitive camera behind the sample a sample of a powder pressed into a wafer is spectroscopically more uniform than a catalyst bed of meshed particles. Naturally the contrast becomes more extreme as the meshed particles become larger. Moreover, if the sample is spatially nonuniform then severe constraints are placed on the positional stability of the X-ray beam. Any motion of the position of the X-ray beam will then probe different thicknesses of the sample, with direct consequences on the measured S/N. From the perspective of XAFS spectroscopy, any nonuniformity of the sample thickness could directly affect the accuracy of the measurement of the amplitude of the X-ray absorption coefficient. It is the amplitude that contains information about the coordination number and site disorder. As has been discussed elsewhere (Koningsberger and Prins, 1988), these amplitude distorting effects are given the general heading of "thickness effects." In brief, a thickness effect occurs when part of the incident X-ray beam is not attenuated by the sample. In the case of meshed particles this would be in the form of pinholes in the sample. 

The earliest diffraction photographs used a stationary nonmonochro-matic X-ray source, a stationary or almost-stationary crystal, and a stationary planar X-ray-sensitive film (masked from ambient light by black paper) this was the Laue141 camera. The first diffraction by NaCl was initially misinterpreted (the scattering power of Cl and Na is almost the same). The most intense Ka radiation of a Coolidge142 water-cooled X-ray tube could be selected by thin filters, which absorbed K[1 and a fair fraction of the continuous Bremsstrahlung white emission (Ni filter for Cu X-rays, Cr filter for Fe, etc.). Later, crystal monochromators (graphite, or LiF) replaced the filters to provide an almost-monochromatic X-ray source beam. 

If the compound does not crystallize, then diffraction by a powder is the only recourse The Scherrer powder camera has a strip of X-ray-sensitive film... 

A satisfactory crystal is exposed to X-rays while held in the vapor phase of the liquid of crystallization or the Mother liquor" as shown iiFig. 5.2. The crystal is sealed in a thin-walled glass capillary between two layers of liquid. Orientation of the crystal with respect to the X-ray beam is changed by rotation or oscillation so that the constructive interferences from groups of atoms in different planes of the crystal are recorded by the X-ray detector represented by a sheet of X-ray sensitive photographic film in Fig. 5.2. 

Fig. la-c. X-Ray diffraction patterns of the body centered cubic (Aspect No. 8) phase from hydrated monoolein recorded on X-ray sensitive film (a) and monoelaidin recorded on Kodak image plates (b). A 360° radial average of the scattered X-ray intensity recorded in (b) is shown in (c) at relative magnifications of xl and x3.2. Radial position is shown in units of mm corresponding to the actual distance on the image plate from the center of the pattern. The patterns in (a) and (b) were recorded with exposures of 15 min and lO s, respectively... 

Rudolph, N. S., Latt, S. A. (1989). Flow cytometric analysis of X-ray sensitivity in ataxia telangiectasia. Mutation Research, 211, 31-41. 

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