Tidal effects

NGC 6822 is an isolated irregular galaxy of the Local Group located at 495 kpc from our Galaxy and at 880 kpc from M31, there are no small galaxies in its neighbourhood, and it does not show tidal effects. 

Early in the development of the theory of nucleosynthesis, an alternative to the high-T r-process canonical model (Sects. 7.1 and 7.2) has been proposed [63], It relies on the fact that very high densities (say p > 1010 gem-3) can lead material deep inside the neutron-rich side of the valley of nuclear stability as a result of the operation of endothermic free-electron captures, this so-called neutronisation of the material being possible even at the T = 0 limit. The astrophysical plausibility of this scenario in accounting for the production of the r-nuclides has long been questioned, and has remained largely unexplored until the study of the composition of the outer and inner crusts of neutron stars and of the decompression of cold neutronised matter resulting from tidal effects of a black hole on a neutron-star companion ([24] for references). The decompression of cold neutron star matter has recently been studied further (Sect. 9). 

Near shore, the interaction between the ocean and coastal rivers results in the formation of fresh-salt water interfaces, known as estuaries. Depending on coastal geology, they can assume various forms, such as fjords, drowned river valleys, or bar-built estuaries, characterized by barrier islands. Tidal effects, storms, and the mixing, or lack thereof, of salt water and freshwater strongly influence the biology... 

DIRECT AND INDIRECT TIDAL EFFECTS ON (ABSOLUTE) HEIGHTS... 

Table 5. Tidal effects on orthometric or normal heights.

From the above results we see that tidal effects on absolute heights amount up to several decimetres and are not negligible considering the presently achievable precision of observations. ... 

In most practical applications the variations of height differences in local regions are much more important than the variations of absolute heights. GPS positioning first of all provides three-dimensional baselines. Thus, tidal effects on ellipsoidal height differences over baseline lengths of some 10 to some 100 km have to be considered ... 

Considering these problems, three concepts have been proposed with respect to the treatment of the permanent tidal effects. In the "non-tidal" case, recommended in a lAG Resolution of 1979, any direct and indirect effects, periodic and permanent, are reduced for. It is evident that this concept relies on the secular Love numbers ho, ko due to the disadvantages discussed above this approach is unsuitable from theoretical and practical points of view. 

Rapp, R. H. (1989). The Treatment of Permanent Tidal Effects in the Analysis of Satellite Altimeter Data for Sea Surface Topography. Manuscr. Geod., 14, 368-372. 

Hodgkiess et al [78] exposed glass fibre reinforced laminates to (i) distilled water, (ii) simulated sea water ( Ocean Salt 3.3% total dissolved solids) (iii) simulated spray/sunlight conditions in the laboratory and (iv) to tidal effects and permanent immersion in the lower Clyde estuary (55°45 N 4°55 W), where the sea water temperature was 6-12°C over the period of testing. The materials tested, which were exposed for up to 18 months with all sides and edges coated in the same resin, were ... 

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