Beta loss peak

Physical aging affects significantly the mechanical damping in both the alpha and beta relaxation peaks. Figure 19 shows the decrease in the beta loss peak as a func-... 

The volumetric, elastic and dynamic properties of internally and externally plasticised PVC were studied and compared with those of unplasticised PVC. The glass transition temperature for the plasticised samples was markedly lowered and this decrease was more important for the externally plasticised ones. The positions of the loss peaks from dielectric alpha-relaxation measurements confirmed the higher efficiency of the external plasticisation. However, the shape of the dielectric alpha-relaxation function was altered only for the internally plasticised samples. The plasticisation effect was linked with a decrease in the intensity of the beta-relaxation process but no important changes in the activation energy of this process were observed. The results were discussed. 47 refs. 

Esters Rather weak intensity Base peak3 at m/e equal to the mass of R-C=0 peaks at m/e equal to the mass of 0=C-0R, the mass of OR and R McLafferty rearrangement possible in case of (1) presence of a beta hydrogen in R (peak at m/e equal to the mass of R-C( OH)OH, and (2) presence of a gamma hydrogen in R peak at m/e equal to the mass of (CH2=C( OH)OR) loss of 42 (CH2=C=0) in case of benzyl esters loss of ROH via the ortho effect in case of o-substituted benzoates... 

The location of berkelium, a beta emitter which cannot be monitored, can be estimated from the position of the californium in the column, as determined by the neutron peak (from 2 2cf), during the time that curium is in the effluent solution. Typical neutron peaks are shown in Fig. 2. By comparison of the relative distribution coeffients of the actinides, the berkelium location is known to be about midway between californium and curium. The last 5-10% of the americium-curium is purposely routed into the transcurium element product tank to minimize the berkelium loss. Subsequently, this americium-curium is recovered in a second-cycle LiCl AIX run. 

Amines Hardly detectable in case of acyclic aliphatic amines high intensity for aromatic and cyclic amines Beta cleavage yielding >C=Nv base peak for all 1° amines at m/e = 30 (CH2=N+H j moderate M-1 peak for aromatic amines loss of 27 (HCN) in aromatic amines fragmentation at alpha carbons in cyclic amines... 

Aromatic hydrocarbons (arenas) Rather Intense Loss of side chain formation of RCH=CHR (via McLafferty rearrangement) cleavage at the bonds beta to the aromatic ring peaks at m/e = 77 (benzene ring, especially monosubstituted) and 91 (tropyllium) the ring position of alkyl substitution has very little effect on the spectrum... 

Figures 13.6(a) and (b) show the alpha and beta transitions obtained in dielectric thermal analysis of PET. The alpha transition (Tg) is affected by the large-scale micro-Brownian motion in the amorphous (non-crystalline) phase. The Brownian motion is observed as a peak in the 1 Hz loss factor cnrve at about 90 °C. The beta transition is considered to be a resnlt of main-chain motion involving the ester groups.

The XRD scans of the parent beta zeolite support as a function of temperature/ scan interval are compiled in Fig. 5.1. The initial increase of the intensity from room temperature to 253 °C (Scan numbers = 1-6 in Hg. 5.1) for the peak at 20-7.5° can be attributed to dehydration of water from the zeolite [38]. The peak maintains its intensity until 415 °C (Scan number = 9 in Fig. 5.1). Above this temperature, a slow decline in the peak intensity can be seen, suggesting a gradual loss of crystallinity. The trend is slightly different for the diffraction at 20-22.8° and other peaks. Their intensity remains relatively constant until the temperature reaches 600 °C (Scan number = 13 in Fig. 5.1). Thereafter, a slow decrease in the intensity becomes noticeable. All these reflection peaks (including the one at 20-7.5°) however, remain even after 1 h dwell at 970 °C. This indicates that the material still maintains its framework structure. Indeed, a final XRD scan of the sample when it is cooled to room temperature reveals that the zeolite structure remains relatively intact, although it does show about a 40 % loss in intensity compared to the XRD pattern before the heat treatment. Nevertheless, the beta zeolite sample used in this study has good thermal stability. 

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