High pressure structure Elastic behavior Synchrotron X-ray powder diffraction a b s t r a c tThe elastic behavior of H-ZSM-5 was investigated by in-situ synchrotron X-ray powder diffraction, using both silicone oil (s.o.) and (16:3:1) methanol:ethanol:water (m.e.w.) as ''non-penetrating'' and ''penetrating'' pressure transmitting media, respectively. From P amb to 6.2 GPa the volume reduction observed in s.o. is 16.6%. This testifies that H-ZSM-5 is one of the most flexible microporous materials up to now compressed in s.o. Volume reduction observed in m.e.w. up to 7.6 GPa is 14.6%. A strong increase in the total electron number of the extraframework system, due to the penetration of water/ alcohol molecules in the pores, is observed in m.e.w. This effect is the largest up to now observed in zeolites undergoing this phenomenon without cell volume expansion. The higher compressibility in s.o. than in m.e.w. can be ascribed to the penetration of the extra-water/alcohol molecules, which stiffen the structure and contrast the channel deformations.

High temperature structural behavior of a natural chabazite of composition (Ca 1.1 Na 0.4 K 0.7 )-[Si 8.6 Al 3.4 O 24 ] • 14.4H 2 O has been characterized by means of in situ HT single-crystal X-ray diffraction (SC-XRD) and thermogravimetric analysis. Lattice dimensions have been measured in the 25-700 °C range and crystal structure refined from XRD data collected at T ) 25, 100, 125, 175, 250, 300, 425, and 600 °C. Variations of unit-cell parameters as a function of temperature reveal two discontinuities at 100 and 200 °C, to which no symmetry changes are associated, and an overall volume reduction of 2.8%. Between 200 and 250 °C, a steep contraction of cell volume is associated with a significant broadening of diffraction profiles, which turn sharp and narrow at higher temperatures. As the dehydration process proceeds with increasing T, cationic sites partly coordinated by extraframework water molecules become unstable and cations migrate toward new positions. Cations occupying the C2, C3, and C4 sites at room temperature move first toward C2 while T is raised to 200 °C, and for T > 200 °C they start migrating toward smaller cavities where coordination is assured by oxygen atoms of the framework only, the sixmembered double ring (C1 site), and a peripheral position within the eight-membered ring. The latter position has been labeled as C5. Sites C1 and C5 are stable up to 700 °C. Reversal experiments demonstrated that the whole process is reversible under the conditions of this study; by decreasing temperature, water enters the structure again and cations migrate back to their original positions.

Cesium can be encapsulated in crystalline aluminosilicates or borosilicates of ANA framework type by hydrothermal synthesis from alkaline solutions at a temperature as low as 115°C. No miscibility gap is observed in the borosilicate-aluminosilicate solid solution. The presence of cesium in the synthesis batch slightly decreases the yield of incorporation of boron in the silicate framework. Nanocrystals from 25 to 50 nm are formed in most of the synthesis conditions.

In 14 patients with early carpal tunnel syndrome, the diagnostic sensitivity of the measurement of the segmental sensory nerve conduction velocity at 1 cm. steps ("inching") was compared with the distal sensory latency and the pre-operative wrist-digit and wrist-palm S.C.V. and with similar measurements made at operation immediately after surgical decompression of the nerve. Before operation, distal sensory latency and wrist-digit S.C.V. were normal in all cases, while wrist-palm S.C.V. was pathological in five patients and inching in all 14 patients. Moreover, inching allowed us to determine the site of the slowing across the carpal tunnel, this being between 1-2 cm. from the distal wrist crease in 57% and between 2-3 cm. in 21% of cases. Focal slowing disappeared immediately after decompression in five patients, as is evident from the intra-operative recordings. Inching is, therefore, the most sensitive diagnostic method in early carpal tunnel syndrome.