Internal structure-insensitive

For pure MMT in FT-IR several internal structure insensitive vibrations of TO4 tetraedra are seen. Asymmetric and symmetric stretch vibrations at 1044cm and 720-650 cm and vibrations of the T-0 bond at 524 and 466 cm are seen. External structure sensitive vibrations between individual TO4 tetraedra occurs as asymmetric stretch vibrations at 918 cm and symmetric stretch vibrations at 798 cm are seen. FT-IR and FT-Raman vibration modes for linear or bent Fe-O-Fe (180° or 110°) can be distinguished and are seen at 900 and 700 cm for (Pe-o-Fe) at 350 and 550 cm for (pe.o-Fe)> respectively [2-3]. 

They concluded that the infrared spectrum contained vibrational modes from both structure insensitive internal tetrahedra and structure sensitive external linkages. The exact frequency of these bands depends on the structure of the zeolite as well as its silicon to aluminum raho (Si/Al). A typical framework IR spectrum for a Y zeolite sample is shown in Figure 4.17. The accepted band assignments and frequency ranges are shown on the figure. 

INTERNAL TETRAHEDRA - STRUCTURE INSENSITIVE 2- EXTERNAL LINKAGES- STRUCTURE SENSITIVE... 

The FTIR spectra of the imcalcined samples between 400 and 1300 cm" are shown in Figure 2. The broad bands in the range of 1000 - 1200 cm" and that at 450 cm" are attributed to structure insensitive internal tetrahedron vibrations [10], while the band present at 800 cm" is attributed to structure insensitive internal tetrahedron or structure sensitive external tetrahedron vibrations [10]. The shoulder observed at 960 cm" indicates the presence of terminal silanol groups on the surface of the mesopore walls [11]. A structure sensitive band, which appears in the spectra around 546 cm" [10], indicates the presence of typical five ring units of the ZSM-5 structure [12]. 

The bands at 1230, 1060 and 450 cm are structure insensitive internal tetrahedron vibrations [11], while the band at 800 cm might be attributed to structure insensitive internal tetrahedron or to structure sensitive external... 

The observed bands were classified by Flanigen et al. [112] into two types, namely internal modes of the TO4 tetrahedra ( intra-tetrahedral modes, cf. Sect 5.2) and external modes ( inter-tetrahedral modes) of the zeolite fi-amework. Table 1 summarizes the zeolite infrared assignment according to the FKS correlation. The internal vibrations represent structure-insensitive modes, and no distinction has been made between the modes of Si04 and AIO4 tetrahedra. The bands of external modes were observed to be sensitive to the structure, and their positions in the spectra are shifted in dependence on the framework topology and on the nsi/n i ratio. Even though this classification proved to be very successful in many applications, from a theoretical point of view such a division into... 

Figure 1. Infrared assignments illustrated with the Y spectrum. Full lines internal TO4 structure insensitive. Dashed lines external TO4 linkages structure sensitive.

Table 8 displays the computed internal energy and specific heat at constant volume. The fact that these agree well with each other, and with experiment, despite the differences in local structure of liquids based on the two potentials emphasizes the insensitivity of thermodynamic properties (except pressure) to structural details. 

A new insensitive, cast-cured PBX called -135, has been developed in order to meet the requirements of US Navy s Insensitive Munitions Advanced Development Programfor High Explosives (IMAD/HE). PBXIH-135 has enhanced internal blast performance, improved non-vulnerability and penetration survivability characteristics compared with PBXN-109. Thermobaric explosives are required to defeat hard and deeply buried structures. PBXIH-135 thermobaric explosive which not only offers effective blast and thermal effects, but is also extremely insensitive to factors responsible for accidental detonation during transit or storage, may also be used for this purpose. 

The experiment is applied for the evaluation of C T, values. T, values are usually used to optimize insensitive C experiments, i.e. to adjust the length of the preparation time in other NMR experiments. To deduce structural information it is usual to interpret the dipolar part of the longitudinal relaxation time (T, ). To separate the dipolar contribution from the contributions of other relaxation mechanisms, it is necessary to perform further experiments (gated decoupling experiments) to evaluate the heteronuclear NOE values. T °° may be exploited in a qualitative way to differentiate between carbon nuclei in less or highly mobile molecular fragments. In a more detailed analysis reliable T, values can be used to describe the overall and internal motions of molecules. 

One redox species is chemically insensitive with respect to variation in E1/2, e.g. a ferrocene derivative, and serves as an internal reference in a linear sweep voltammogram. The second species is chemically sensitive, e.g. a pH sensitive quinone or a CO sensitive ferraazetine derivative, which has an E1/2 that varies with the changes in the chemical environment. A linear sweep voltammogram thus shows two waves, one for the reference molecule and one for the indicator molecule. The shift for the indicator wave along the potential or current axis provides a method for analyte detection. Surface derivitization, proof-of-structure, and proof-of-concept sensor functions are demonstrated. 

The GRIND descriptors are insensitive to the chirality of the structures. This has the undesirable side effect of providing exactly the same description for the two enantiomers associated with any chiral center. Diastereomers might, on the contrary, produce different correlograms, due to the presence of differences in the internal geometry. 

For each cluster size n an initial configuration was chosen to match the minimum energy structure reported by Hoare and Pal. For the classical internal energy approximately 100,000 Monte Carlo moves were made, followed by approximately 1 million moves where data were accumulated in the evaluation of the energy. The constraining radius required to evaluate Eq. (3.1) was taken to be 3a for 2-, 3-, ad 4-particle clusters, 4cluster sizes from 5 to 16, and 5a for cluster sizes from 17 to 20. As shown by Lee, Barker, and Abraham, the calculated free energies are insensitive to the choice of... 

---