Egg shell thinning

Egg shell thinning and reduced duckling survival Waters et al. (1977) ... 

Despite the social and economic benefits of these compounds, problems developed because some of these compounds, once released, did not degrade in the environment. Because of their environmental persistence, some of these compounds have had unintended consequences for example, DDT caused egg shell thinning and thus affected the reproduction of certain types of birds. This problem was brought to the public s attention by the famous book Silent Spring Perhaps as a result, many of these early pesticides are no longer on the... 

Note that this is the para para (abbreviated as p,p ) isomer. The term para means that the chlorine atoms are positioned on the benzene ring across from the linkage to the rest of the molecule. DDT won Paul Muller the Nobel Prize in medicine in 1948 for malaria control because DDT killed the mosquitoes that transmitted this disease. At least 2 billion kilograms of DDT has been used worldwide since about 1940. Because of problems with calcium metabolism in birds (egg shell thinning), DDT has been banned in most industrialized countries since about 1970-1975. By the loss of HC1, p,//-DDT degrades relatively quickly to DDE (see below), which is almost permanently stable in the environment. DDT, however, is still produced and used to control malaria in developing countries because it is cheap to manufacture and simple to use. 

This test probably would not pick up long-term effects caused by bioaccumulation. Populations of animals can also be decimated by chemical effects that do not kill the animals (e.g., the egg shell thinning of birds at the top of the food chain, feminization of males, and behavioral changes, such as not feeding or protecting the young, or losing the ability to avoid predators). 

Egg shell thinning Yes DDT, DDE, Dicofol Wide variation in sensitivity related to reproductive success... 

Wiemeyer SN, Lamont TG, Bunck CM, Sindelar CR, Gramlich FJ, Fraser JD, Byrd MA. 1984. Organochloride pesticide, polychlorobiphenyl, and mercury residues in bald eagle eggs — 1969-1979 — and their relationships to shell thinnings and reproduction. Arch Environ Contam Toxicol 13 529-549. 

Cooke A.S. Shell Thinning in Avian Eggs by Environmental Pollution // Environ. Pollut. 1973. Vol. 4. Issue 2. P.85-152. 

Steam reforming is a heterogeneously catalyzed process, with nickel catalyst deposited throughout a preformed porous support. It is empirically observed in the industry, that conversion is proportional to the geometric surface area of the catalyst particles, rather than the internal pore area. This suggests that the particle behaves as an egg-shell type, as if all the catalytic activity were confined to a thin layer at the external surface. It has been demonstrated by conventional reaction-diffusion particle modelling that this behaviour is due to... 

Wiemeyer, S.N., C.M. Bunck, and A.J. Krynitsky. 1988. Organochlorine pesticides, polychlorinated biphenyls, and mercury in osprey eggs — 1970-79 — and their relationships to shell thinning and productivity. Arch. Environ. Contam. Toxicol. 17 767-787. 

Wiemeyer, S.N., T.G. Lamont, C.M. Bunck, C.R. Sindelar, FJ. Gramlich, J.D. Fraser, and M.A. Byrd. 1984. Organochlorine pesticide, polychlorobiphenyl, and mercury residues in bald eagle eggs — 1966-79 — and their relationships to shell thinning and reproduction. Arch. Environ. Contam. Toxicol. 13 529-549. Wolfe, J.L. and B.R. Norment. 1973. Accumulation of mirex residues in selected organisms after an aerial treatment, Mississippi, 1971-1972. Pestic. Monitor. Jour. 7 112-114. 

In the same context the phenomenon of egg shell reduction has been discussed since thin egg shells are correlated with changed protein profiles of the biocrystalline layer. 

SUBGROUP II.ii FORMATION OF THE TAENIA-TYPE EGG This type of egg is formed essentially in the same way as that of the previous group, only one vitelline cell becoming associated with the fertilised ovum. The embryonic capsule is very thin and almost invisible when laid it is normally lost in faecal eggs. As pointed out earlier, lack of protection by an egg shell is compensated for by the development of a thick embryophore made up of keratin blocks (Fig. 7.1(c)) held together by a cementing substance (442). This gives the egg its characteristically radially striated appearance. 

The catalyst plays a crucial role in technology. Previously, catalysts were based on palladium of 1 to 5 wt% impregnated on silica with alkali metal acetates as activators. Modern catalysts employ as enhancers noble metals, mostly gold. A typical Bayer-type catalyst consists of 0.15-1.5 wt% Pd, 0.2-1.5 wt% Au, 4-10 wt% KOAc on spherical silica particles of 5 mm diameter [14], The reaction is very fast and takes place mainly inside a thin layer on the particle surface (egg-shell catalyst). 

In 1962 The Silent Spring, written by Rachel Carson, was published. Carson s book was one of the first that attracted national attention to the problems of toxic chemicals and the effects of these chemicals on the environment. The Silent Spring recounted how the residues of the pesticide DDT could be found throughout the food chain. In aquatic birds, high levels of DDT were associated with reduced fertility. DDT affected the deposition of calcium in avian ovaries, leading to egg shells too thin to survive, thus causing a widespread reduction in many bird species. 

As soon as the hot egg is exposed to cooler air, the temperature of (he outer surface of the egg shell drops somewhat, and the temperature of the air adjacent to the shell rises as a result of heat conduction from the shell to (he air. Consequently, the egg is surrounded by a thin layer of warmer air, and heat is then transfened from this warmer layer to the outer layers of air. The cooling process in tltis case is rather slow since the egg would always be blanketed by warm air, and it has no direct contact with tlie cooler air farther away. We may not notice any air motion in the vicinity of the egg, but careful measurements would indicate otherwise. 

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