Holocene tectonic histories for five islands in the south-central Lau group, south Pacific

Low-level (<30 m) evidence for emergence is reported for five islands along the south-central Lau Ridge, which has a well-documented history of late Cenozoic uplift. Most of the evidence is erosional, some of the lowest is emerged reef and beachrock: all can be linked to higher relative sea levels. Correlations are established between islands and most of the series of emerged shorelines found to exhibit characteristics of coseismically uplifted series elsewhere. Dates for various shorelines allow ages and recurrence intervals of coseismic-uplift events to be tentatively established for all islands. By reconciling this with contemporary sealevel changes, magnitudes of coseismic uplift are obtained for the middle and late Holocene. The islands of Moce and Oneata have experienced fewest coseismic-uplift events with small uplift magnitudes. Four coseismic-uplift events are identified for Lakeba with an average magnitude of 2.63 m and an assumed recurrence interval of 1045 years: no uplift has apparently occurred since 3800 BP. Five coseismic-uplift events are identified for Namuka-i-Lau with an average magnitude of 2.08 m and an assumed recurrence interval of 1045 years: no uplift has apparently occurred since 2360 BP. Three coseismic-uplift events occurred on Nayau, averaging 1.53 m in magnitude and recurring every 1045 years: no uplift has occurred since 2240 BP. The approach used here has implications not only for understanding tectonic history but may eventually prove a useful tool for isolating Holocene sealevel history in tectonically active areas. © 1995, Sage Publications. All rights reserved

Role of photoadduct of K4 Fe(CN)6 and C3 H4 N2 in improving thermal stability of polyaniline composite

This paper involves the synthesis of polyaniline composite with photoadduct of potassium hexacyanoferrate and imidazole via photochemical route by oxidative polymerization technique by ammonium persulphate. The photoadduct has been synthesized by photoirradiation followed by substitution with imidazole ligand. The photoaquation, substitution and successful synthesis has been proved by recording pH, UV visible spectra before and after irradiation and XRD of photoadduct. The as synthesized composite has been subjected to various characterizations like elemental analysis, UV–Visible spectra, FTIR, XRD, SEM, and TG/DTG. XRD of photoadduct shows crystalline structure which has been retained in the composite, changing the amorphous structure of polyaniline into the crystalline one, hence proving the insertion of photoadduct in the polymer chain. Various parameters like crystallite size (L), interplanar distance (d), micro strain (ε), dislocation density (δ) and distortion parameters (g) were calculated from XRD data. Thermal analysis shows the high thermal stability of composite which can be due to strong interaction between polymer chain and the photoadduct which restricts the thermal motion of polyaniline and thus enhances the thermal stability of composite