METALS IN NUTRITION

METALS IN NUTRITION

Metals in the diet

A variety of metals are found in a range of foods in the diet, and in this context, are termed minerals, along with some non-metals, such as iodine and fluorine. The minerals are grouped in to either: Macro minerals – those that are needed by the body in relatively large amounts (e.g. sodium, potassium, chlorine, calcium, phosphorus, magnesium) Micro/trace minerals – those needed in small amounts (e.g. selenium, iron, zinc, copper, manganese, molybdenum, chromium, arsenic, germanium, lithium, rubidium, tin). Many of these minerals have been classed as essential elements, necessary for utilisation by the body to ensure good health, but the function of these minerals and their benefits to the body is still uncertain and has been widely speculated. This has given scope for arguing the justification of taking supplements. Much research has been carried out, concerning the role of minerals in the body, but in many cases, difficulties in investigating their individual effects has been expressed because intake is often in combination with other vitamins and minerals, e.g. fruit and vegetables contain several minerals. There is, however, strong evidence that supplementation of certain minerals would benefit those suffering from deficiency disorders. It is also important to note though that intake of minerals does not necessarily correlate with absorption and a balance must be obtained. There are many suggested essential elements – here, we have highlighted some of those which have been most speculative, primarily the micro minerals.

Macro minerals

Macro minerals are present in virtually all cells of the body, maintaining general homeostasis and required for normal functioning. Acute imbalances of these minerals can be potentially fatal, although nutrition is rarely the cause of these cases. Diet can affect levels of macronutrients in the body, but effects are generally chronic, e.g. a high intake of sodium can lead to hypertension.

Micro minerals

Micro minerals contribute to good health if they originate from an organic source because they have essentially been processed. Plants take up minerals from the ground, digest them, making them ionic so that when consumed by humans, assimilation into the body occurs much more easily, and toxicity by accumulation does not occur. However, micro minerals from inorganic sources, such as heavy metals, can not be used by the body as they tend to build up in the tissues.

Understanding of superconductivity may be closer

Understanding of superconductivity may be closer

Phys­i­cists have long de­bat­ed the causes of su­per­con­duc­tiv­ity, a phe­nom­e­non in which nor­mal re­sist­ance to a flow of elec­tri­cal cur­rent van­ishes in cer­tain ma­te­ri­als when ex­tremely cold. This al­lows hyper-efficient cur­rent trans­mis­sion—of­fer­ing the prom­ise of a new elec­tri­cal gold­en age with high-pow­ered com­put­ers, mag­net­ic­ally lev­i­tat­ing trains and super-efficient pow­er lines. But to put this ef­fect to prac­ti­cal use, sci­en­tists have to un­der­stand it bet­ter, es­pe­cially why it seems to oc­cur only in such cold and wheth­er that can be changed. A new study may help clar­i­fy these ques­tions, ac­cord­ing to re­search­ers who have found that su­per­con­duc­tiv­ity works dif­fer­ently in two slightly dif­fer­ent tem­per­a­ture ranges. Su­per­con­duc­tiv­ity was dis­cov­ered by the Dutch phys­i­cist Heike Kamer­lingh Onnes when in 1911 when he cooled mer­cu­ry to barely above ab­so­lute ze­ro, the low­est tem­per­a­ture the­o­ret­ic­ally pos­si­ble. Sci­en­tists lat­er con­clud­ed that su­per­con­duc­tiv­ity at such rock-bot­tom tem­per­a­tures oc­curs when vibra­t­ions of the grid-like atom­ic ar­range­ment of the ma­te­ri­al af­fects its elec­trons, suba­tom­ic par­t­i­cles that car­ry elec­tric charge. These, which nor­mally re­pel each oth­er be­cause they have the same charge, then join up as pairs that glide ef­fort­lessly through the ma­te­ri­al with­out scat­ter­ing off its at­oms. In 1986 came the dis­cov­ery of a class of ma­te­ri­als that al­low su­per­con­duc­tiv­ity at some­what less frig­id tem­per­a­tures: up to about 150 Kel­vin (mi­nus 253 F or mi­nus 123 C), con­sid­erably high­er than the 4 de­grees Kel­vin (mi­nus 452F or mi­nus 269 C) re­quired in the orig­i­nal Onnes tests. This ad­vance al­lowed the ma­te­ri­als to be cooled with liq­uid ni­tro­gen, which costs less than the liq­uid he­li­um needed to cool low­er-tem­per­a­ture su­per­con­duc­tivity. Since that find­ing, sci­en­tists have de­bat­ed wheth­er in these higher-tem­per­a­ture su­per­con­duc­tors—al­so called cop­per ox­ide su­per­con­duc­tors—elec­trons bond in the same ways as in the low­er-tem­per­a­ture su­per­con­duc­tors. The mech­an­ism turns out to be dif­fer­ent, ac­cord­ing to the new stu­dy. Rath­er than atom­ic vibra­t­ions driv­ing the elec­trons to join as pairs, the re­search­ers said, higher-tem­per­a­ture su­per­con­duc­tiv­ity de­pends on elec­trons’ abil­ity to take ad­van­tage of their nat­u­ral re­pul­sion in a com­plex situa­t­ion. This con­clu­sion, in­ves­ti­ga­tors said, was based on ex­pe­ri­ments show­ing that the places in a sam­ple where elec­trons form the most strongly bound pairs, are the same as where they show signs of stronger re­pul­sion at higher, non-su­per­con­duct­ing tem­per­a­tures. Sur­pris­ing­ly, in oth­er words, it seems “the elec­trons with the strongest re­pul­sion in one situa­t­ion are the most ad­ept at su­per­con­duc­tiv­ity in anoth­er,” said Prince­ton Uni­ver­s­ity phys­i­cist Ali Yaz­dani, one of the re­search­ers. That’s un­like the be­hav­ior of elec­trons in low­er-tem­per­a­ture su­per­con­duct­ive ma­te­ri­als, ac­cord­ing to the group, which stud­ied a com­pound made of stron­ti­um, bis­muth, cal­ci­um and cop­per ox­ide and re­ported the find­ings in the April 11 is­sue of the re­search jour­nal Sci­ence. Al­though much re­mains to be ex­plained, the re­search­ers said their work may be a a use­ful step. “The da­ta is a gold mine which we’re only be­gin­ning to ex­ploit,” agreed Prince­ton phys­i­cist Phil­ip An­der­son, who won a phys­ics No­bel in 1977 and was­n’t in­volved in the re­search. The in­ves­ti­ga­tors used a spe­cially rigged form of a de­vice known as scan­ning tun­nel­ing mi­cro­scope, which let them ex­am­ine a sin­gle at­om as elec­trons there went from re­pelling each oth­er to pair­ing up. The mi­cro­scope an­a­lyzes at­oms by meas­ur­ing cur­rent that flows be­tween the sur­face of a sam­ple, and a spe­cially de­signed probe on the mi­cro­scope. The probe, with a fi­ne tip just one at­om wide, is placed a hair’s breadth above the sam­ple, and can move in in­cre­ments smaller than an at­om over the sur­face to take mea­sure­ments. April 10, 2008,Courtesy Princeton University and World Science staff

Superinsulator - New State of Matter

Superinsulator - New State of Matter Physicists have known about superconductors since 1911, but now it looks like the opposite - a superinsulator - might also exist, unnoticed until recently. An international team led by Argonne National Laboratory's Valerii Vinokur has published their findings in the April 3 issue of the journal Nature. The superinsulator requires a very delicate balance to be achieved. Thin films of titanium nitride (normally a superconductor) apparently drop to zero electrical conductance when lowered below a certain critical temperature and placed in the presence of a magnetic field, the exact opposite of what occurs in standard superconductivity (which yields zero electrical resistance below a critical temperature). Scientists have known that superconductors can turn into insulators, but only due to quantum phase transitions very near absolute zero. This new form of insulator extends over a range of temperatures up to nearly 70 millikelvin in a magnetic field of 0.9 tesla. The theory behind these results poses some curious properties of quantum physics, as is usually the case. Essentially, they posit that electrical current and electrical voltage swap roles in the quantum system under these conditions. Plotting phase diagrams of current vs. magnetic field for superconductors and voltage vs. magnetic field for superinsulators result in a pair of phase diagrams which appear to be virtually identical, in fact! In an analysis of the findings, Italian physicist Rosario Fazio says, "Vinokur and colleagues' observation and theory of superinsulation are crucial advances in our understanding of the collective properties of low-dimensional systems." Fazio goes on to speak about the extent to which further investigation into these topics needs to be performed. One does have to wonder what technological insights we might gain from the intense study of how to create materials which can completely block the flow of electrical impulses

Power goes wireless

A new sys­tem for trans­mit­ting pow­er could get rid of the tan­gle of ca­bles that keep alive our cell phones, lap­tops and oth­er de­vices, re­search­ers re­port. Phys­i­cists at the Mas­sa­chu­setts In­sti­tute of Tech­nol­o­gy in Cam­bridge, Mass. found that pow­er could be trans­mit­ted with­out wires us­ing spe­cial “res­o­nant” an­ten­nas. The re­search­ers used the sys­tem to pow­er a 60-watt light bulb more than two me­ters (a­bout two yards) from a wire­less trans­mit­ter at 40 per­cent ef­fi­cien­cy. Two im­ages of a 60-watt bulb lit from 2 me­ters away by a pow­er-trans­mit­ting coil. Note the ob­s­truc­tion in the low­er im­age.One known meth­od uses elec­tro­mag­ne­tic radia­t­ion, like ra­di­o waves. More com­monly used for wire­less trans­mis­sion of in­forma­t­ion, these can al­so trans­mit pow­er. But not very ef­fec­tive­ly. Since radia­t­ion spreads in all di­rec­tions, al­most all the pow­er would end up be­ing wast­ed in­to space. An al­ter­na­tive strat­e­gy is to beam the radia­t­ion spe­cif­ic­ally to­ward the elec­tron­ic de­vice to be charged—but then prob­lems can arise if some oth­er ob­ject gets in the way, or if you move the de­vice. The MIT con­cept, called “WiTricity” for wire­less elec­tricity, in­volves us­ing so-called cou­pled res­onators. These are ob­jects that, if struck or dis­turbed, tend to nat­u­rally os­cil­late at a def­i­nite rhythm. If two of them tend to have match­ing rhythms, they ac­tu­ally en­hance each oth­ers’ os­cilla­t­ions. One ex­am­ple is a child on a swing. If she swings her legs in synch with the nat­u­ral rhythm of the swing it­self, the swing will soon be briskly in mo­tion. The type of res­o­nance be­hind such a push-pull sys­tem is called me­chan­i­cal, but oth­er types of res­o­nances are pos­si­ble. There are acous­tic res­o­nances, for ex­am­ple. Im­ag­ine a room with 100 iden­ti­cal wine glass­es, each filled with dif­fer­ent amounts of wine. This gives each glass a dif­fer­ent “res­o­nant fre­quen­cy,” or nat­u­ral rhythm of vibra­t­ion. If a sing­er then sings a loud enough note in the room, a glass of the cor­re­spond­ing fre­quen­cy might ac­cu­mu­late enough en­er­gy to ex­plode, while the oth­er glass­es sit un­dis­turbed. The MIT team fo­cused on yet anoth­er type of res­o­nance, mag­net­ic. They set up two cop­per coils, each a self-resonant sys­tem. One coil, at­tached to a pow­er source, is the “send­ing” un­it. In­stead of send­ing out elec­tro­mag­netic waves, it fills its sur­round­ings with an os­cillating mag­net­ic field. This leads to a pow­er ex­change with the oth­er, “re­ceiv­ing” coil. Be­cause the mag­net­ic field, un­like ra­di­o waves, nev­er gets too far from the send­ing un­it, the en­er­gy is­n’t lost in­to space. And ex­tra­ne­ous ob­jects en­ter­ing the field have no im­pact be­cause they nor­mally don’t res­o­nate along with the sys­tem. With such a de­sign, pow­er trans­fer has a lim­it­ed range, and the range would be shorter for smaller-size re­ceivers. Still, for lap­top-sized coils, pow­er lev­els more than enough for a lap­top can be trans­ferred over room-sized dis­tances nearly omni-directionally and ef­fi­cient­ly, re­gard­less of what’s be­tween the ob­jects, re­search­ers said. “As long as the lap­top is in a room equipped with a source of such wire­less pow­er, it would charge au­to­mat­ic­ally, with­out hav­ing to be plugged in,” said MIT’s Pe­ter Fish­er. Al­though the pow­er trans­fer ef­fi­cien­cy re­mains be­low the ide­al, team mem­ber An­dre Kurs said in an e­mail that he’s op­ti­mis­tic it can be im­proved. He al­so ac­knowl­edged that inef­fi­cien­cy raises en­vi­ron­men­tal con­cerns, but ar­gued that the new sys­tem on bal­ance might ac­tu­ally help the en­vi­ronment. That’s be­cause the bat­ter­ies that it would re­place al­so tend to lose ef­fi­cien­cy over time, and con­tain tox­ic chem­i­cals.