Transmission studies

Figures 8 and 9 shows a part of the bending region at low temperature containing the components of Vg (150-160 cm ) and Vs (190-200 cm ). The Vg vibration, IR active in the free molecule, has weak components in the Raman spectrum. According to theoretically calculated Raman intensities, which almost perfectly fit the experimental spectrum, the big component has a very low scattering cross-section [87] and is accidentally degenerate with the b2g component at ca. 188 cm. The IR active components of Vg cause strong absorptions in the IR spectrum even if the crystalline sample used for transmission studies is as thin as 400 pm [107, 109].

The lattice vibrations begin to absorb strongly below 1200 cm". An additional feature at 1072 cm", characteristic of boehmite, is the result of the Al-OH stretch. Both the OH stretches and the Al-OH stretch have been previously identified by transmission studies of boehmite single crystals (19). 

Reflection-Absorption IR spectroscopy (RAIRS) where the linearly polarized IR beam is specularly reflected from the front face of a highly reflective sample, such as a metal single crystal surface (Figure 3.1(a)). This is also sometimes referred to as IRAS (IR reflection absorption). The IR beam comes in at grazing angle (i.e. almost parallel to the surface), and although absorption bands in RAIRS have intensities that are some two orders of magnitude weaker than in transmission studies on... 

It is important to stress that ATR absorbance is strongly affected by the sample/crystal contact. Quantitative results are thus difficult to obtain even if the contact is maintained during the sample rotation that is required to record all four polarized spectra. A reference band that does not show significant dichroism is thus most often used to normalize the polarized absorbances in order to obtain quantitative data. For instance, the 1,410 cm-1 band of PET has often been chosen for that purpose, not only for ATR studies but also for specular reflectance (see below) and even transmission studies when the sample thickness is not uniform. It was shown that an appropriate normalization is possible even if no such reference band is available, by using a combination of two bands with orthogonal dichroism [34]. When performing ATR experiments, one should also make certain that the applied pressure does not create artifacts by affecting the structure of the sample. 

In transmission studies of small aluminum spheres, Batson (22) has shown details of the generation of surface plasmons in the aluminum and in the thin coating oxide layer. Marks (23) and Cowley (24) have examined the surface plasmons and surface state excitations of small MgO smoke crystals. It is clearly evident that these excitations may be produced by electron beams passing the crystal in the vacuum, 3 nm or more away from the surface. 

Thompson, M., C.L. Arthur, and G.K. Dhaliwal. 1986. Liquid-phase piezoelectric and acoustic transmission studies of interfacial immunochemistry. Anal. Chem. 58 1206-1209. 

NBS s involvment in SRM s for gas transmission studies arose out of activities within ASTM Committees D-20 (Plastics) and F-2 (Flexible Barrier Materials) that were aimed at standardizing a new instrumental method employing a coulometric oxygen detector for the measurement of oxygen gas transmission rates in materials used for various kinds of packaging (4 ). A subsequent reevaluation of the precision data for the classical manometric and volumetric methods (5) for gas transmission measurements showed that there are serious problems with the reproducibility and repeatability these methods. The use of SRM 1470 to verify the calibration is currently being written into ASTM standards D-3985 and D-1434. 

The sample thickness in the DIT cells (25 pm) is very large in comparison with the usual thickness of samples for infrared transmission studies, and the cell itself is also thick (2.8 mm). Studies in the attenuated total reflectance (ATR) mode do not fit the experiment. For all these reasons, it was by no means certain that infrared studies could in fact be performed using the existing DIT cells. 

Gibbs, A. J. and Gower, J. C. (1960). The use of a multiple-transfer method in plant virus transmission studies Some statistical points arising in the analysis of results. Annals of Applied Biology, 48, 75-83. 

Position of the center of the NIR in an electron transmission study. The - sign is used to indicate chat Che EA is negative. 

Leafhopper vectors of phytoplasmas infecting papaya are unknown a species of Orosius has been identified as a candidate for transmission studies of papaya diseases in Australia (Padovan and Gibb, 2001). The leafhopper Empoasca papayae has been reported to be a natural vector of papaya bunchy top disease (Davis et al., 1998). 

The X-ray images of extended lattice imperfections within the crystal arise fi om variations in beam intensity caused by local distortions of the lattice. Dislocation densities of up to 10 mm can be resolved in transmission studies or ten times this by the reflection technique. This resolution is lower than that obtainable by transmission electron microscopy, but the sample used may be thicker and does not have to be examined under high vacuum. X-ray beams also produce less radiation damage in the sample. When decomposition proceeds beyond a > 0.01, distortion of the lattice is such that the X-ray image loses resolution and the exposures required become even longer. Reflection data obtained at several different diffraction angles may be required to characterize the imperfections present. 

The ATR-FT-IR method is particularly suitable for the spectroscopic analysis of pharmaceutical tablets, mainly due to the minimal sample preparation required and the possibility of obtaining quantitative chemical informahon from the sample. Such advantages are important with this type of sample, because it is difficult to microtome a tablet into the suitable thicknesses (usually <10 gm) that are often needed for transmission studies. The diffuse-reflechon technique is also often very... 

Kamar N, Mansuy IM, Cointault O, Selves J, Abravanel E, Danjoux M, Otal P, Esposito L, Durand D, Izopet J, Rostaing L (2008) Hepatitis E virus-related cirrhosis in kidney- and kidney-pancreas-transplant recipients. Am J Transplant 8(8) 1744-1748 Kane MA, Bradley DW, Shrestha SM, Maynard IE, Cook EH, Mishra RP, Joshi DD (1984) Epidemic non-A, non-B hepatitis in Nepal. Recovery of a possible etiologic agent and transmission studies in marmosets. JAMA 252 3140-3145 Karron RA, Daemer R, Ticehurst J, D Hondt E, Popper H, Mihalik K, Phillips J, Eeinstone S, Purcell RH (1988) Studies of prototype live hepatitis A virus vaccines in primate models. J Infect Dis 157(2) 338-345... 

The above combinations of molecular determinants and phenotypic sets are considered typical subgroups, or even strains, of disease that have been confirmed. Transmission studies of human cases are complicated by the observation that after inter-species transmission, the size and glycoform of the human PrPSc inoculum may change [115, 116]. In a recent review of transmission studies in non-human... 

It is unknown whether CWD1 and CWD2 interfere or act synergistically, or whether their co-existence contributes to the unparalleled efficiency of CWD transmission. Interestingly, previous CWD transmission studies in transgenic... 

Early transmission studies to Tg(MHu2M)5378 mice provided evidence that different human prion strains, in this case in patients with FFI, caused by mutation at codon 178 (D178N), and familial CJD, caused by mutation at codon 200 (E200K), are represented by different conformational states of PrPSc [123], a concept first elaborated following transmission of different hamster-adapted strains of TME [124], While this hypothesis is supported by considerable additional experimental evidence, defining human prion strain prevalence has been hampered by difficulties in arriving at an internationally accepted classification system for... 

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