Reduced raindrop-impact driven soil erosion by infiltration

We used a simple laboratory experiment to investigate whether infiltration influences raindrop-impact induced soil erosion. There was substantially less erosion under infiltration conditions than with no infiltration. This was because a "shield" layer of deposited particles developed more rapidly under infiltration compared to "no-infiltration" conditions. Interestingly, the "shield" depth that fully protected the underlying soil from raindrop-impacts was shallower under infiltrating conditions. We found that the Rose soil erosion model captured the erosion dynamics well (R² ≈ 0.9). Predicting the "full-shield" depth remains unresolved. These results add evidence to previous studies indicating that saturated, slowly draining areas in the landscape are particularly susceptible to soil erosion from raindrop impact

Selenium, the thyroid, and the endocrine system.

Recent identification of new selenocysteine-containing proteins has revealed relationships between the two trace elements selenium (Se) and iodine and the hormone network. Several selenoproteins participate in the protection of thyrocytes from damage by H(2)O(2) produced for thyroid hormone biosynthesis. Iodothyronine deiodinases are selenoproteins contributing to systemic or local thyroid hormone homeostasis. The Se content in endocrine tissues (thyroid, adrenals, pituitary, testes, ovary) is higher than in many other organs. Nutritional Se depletion results in retention, whereas Se repletion is followed by a rapid accumulation of Se in endocrine tissues, reproductive organs, and the brain. Selenoproteins such as thioredoxin reductases constitute the link between the Se metabolism and the regulation of transcription by redox sensitive ligand-modulated nuclear hormone receptors. Hormones and growth factors regulate the expression of selenoproteins and, conversely, Se supply modulates hormone actions. Selenoproteins are involved in bone metabolism as well as functions of the endocrine pancreas and adrenal glands. Furthermore, spermatogenesis depends on adequate Se supply, whereas Se excess may impair ovarian function. Comparative analysis of the genomes of several life forms reveals that higher mammals contain a limited number of identical genes encoding newly detected selenocysteine-containing proteins.Journal ArticleResearch Support, Non-U.S. Gov'tReviewinfo:eu-repo/semantics/publishe