Books on the topic 'Aluminium foam'

In all patients with chronic kidney disease (CKD) stages 3–5, regular monitoring of serum markers of CKD-mineral and bone disorder, including calcium (Ca), phosphorus (P), parathyroid hormone (PTH), 25-hydroxyvitamin D, and alkaline phosphatase, is recommended. Target ranges for these markers are endorsed by guidelines. The principles of therapy for secondary hyperparathyroidism include control of hyperphosphataemia, correction of hypocalcaemia, use of vitamin D sterols, use of calcimimetics, and parathyroidectomy. of hyperphosphataemia is crucial and may be achieved by means of dietary P restriction, use of P binders, and P removal by dialysis. Dietary P restriction requires caution, as it may be associated with protein malnutrition. Aluminium salts are effective P binders, but they are not recommended for long-term use, as Aluminium toxicity (though from contaminated dialysis water rather than oral intake) may cause cognitive impairment, osteomalacia, refractory microcytic anaemia, and myopathy. Ca-based P binders are also quite effective, but should be avoided in patients with hypercalcaemia, vascular calcifications, or persistently low PTH levels. Non-aluminium, non-Ca binders, like sevelamer and lanthanum carbonate, may be more adequate for such patients; however, they are expensive and may have several side effects. Furthermore, comparative trials have failed so far to provide conclusive evidence on the superiority of these newer P binders over Ca-based binders in terms of preventing vascular calcifications, bone abnormalities, and mortality. P removal is about 1800–2700 mg per week with conventional thrice-weekly haemodialysis, but may be increased by using haemodiafiltration or intensified regimens, such as short daily, extended daily or three times weekly nocturnal haemodialysis. Several vitamin D derivatives are currently used for the treatment of secondary hyperparathyroidism. In comparison with the natural form calcitriol, the vitamin D analogue paricalcitol seems to be more fast-acting and less prone to induce hypercalcaemia and hyperphosphataemia, but whether these advantages translate into better clinical outcomes is unknown. Calcimimetics such as cinacalcet can significantly reduce PTH, Ca, and P levels, but they have failed to definitively prove any benefits in terms of mortality and cardiovascular events in dialysis patients. Parathyroidectomy is often indicated in CKD patients with severe persistent hyperparathyroidism, refractory to aggressive medical treatment with vitamin D analogues and/or calcimimetics. This procedure usually leads to rapid improvements in biochemical markers (i.e. significant lowering of serum Ca, P, and PTH) and clinical manifestations (such as pruritus and bone pain); however, the long-term benefits are still unclear.

This is an advance summary of a forthcoming article in the Oxford Encyclopedia of Planetary Science. Please check back later for the full article.Although the second most abundant element in the cosmos is helium, noble gases are also called rare gases. The reason is that they are not abundant on terrestrial planets like our Earth, which is characterized by orders of magnitude depletion of—particularly light—noble gases when compared to the cosmic element abundance pattern. Indeed, such geochemical depletion and enrichment processes make noble gases so versatile concerning planetary formation and evolution: When our solar system formed, the first small grains started to adsorb small amounts of noble gases from the protosolar nebula, resulting in depletion of light He and Ne when compared to heavy noble gases Ar, Kr, and Xe: the so-called planetary type abundance pattern. Subsequent flash heating of the first small mm to cm-sized objects (chondrules and calcium, aluminum rich inclusions) resulted in further depletion, as well as heating—and occasionally differentiation—on small planetesimals, which were precursors of larger planets and which we still find in the asteroid belt today from where we get rocky fragments in form of meteorites. In most primitive meteorites, we even can find tiny rare grains that are older than our solar system and condensed billions of years ago in circumstellar atmospheres of, for example, red giant stars. These grains are characterized by nucleosynthetic anomalies and particularly identified by noble gases, for example, so-called s-process xenon.While planetesimals acquired a depleted noble gas component strongly fractionated in favor of heavy noble gases, the sun and also gas giants like Jupiter attracted a much larger amount of gas from the protosolar nebula by gravitational capture. This resulted in a cosmic or “solar type” abundance pattern, containing the full complement of light noble gases. Contrary to Jupiter or the sun, terrestrial planets accreted from planetesimals with only minor contributions from the protosolar nebula, which explains their high degree of depletion and basically “planetary” elemental abundance pattern. Indeed this depletion enables another tool to be applied in noble gas geo- and cosmochemistry: ingrowth of radiogenic nuclides. Due to heavy depletion of primordial nuclides like 36Ar and 130Xe, radiogenic ingrowth of 40Ar by 40K decay, 129Xe by 129I decay, or fission Xe from 238U or 244Pu decay are precisely measurable, and allow insight in the chronology of fractionation of lithophile parent nuclides and atmophile noble gas daughters, mainly caused by mantle degassing and formation of the atmosphere.Already the dominance of 40Ar in the terrestrial atmosphere allowed C. F v. Weizsäcker to conclude that most of the terrestrial atmosphere originated by degassing of the solid Earth, which is an ongoing process today at mid ocean ridges, where primordial helium leaves the lithosphere for the first time. Mantle degassing was much more massive in the past; in fact, most of the terrestrial atmosphere formed during the first 100 million years of Earth´s history, and was completed at about the same time when the terrestrial core formed and accretion was terminated by a giant impact that also formed our moon. However, before that time, somehow also tiny amounts of solar noble gases managed to find their way into the mantle, presumably by solar wind irradiation of small planetesimals or dust accreting to Earth. While the moon-forming impact likely dissipated the primordial atmosphere, today´s atmosphere originated by mantle degassing and a late veneer with asteroidal and possibly cometary contributions. As other atmophile elements behave similar to noble gases, they also trace the origin of major volatiles on Earth, for example, water, nitrogen, sulfur, and carbon.