Showing papers on "Zinc published in 1985"

Calculation of bulk moduli of diamond and zinc-blende solids.

Abstract: Theoretical arguments on the role of covalency in determining the bulk moduli of diamond and zinc-blende semiconductors and insulators are shown to yield a surprisingly simple and accurate expression for determining the bulk moduli B of these materials. One resulting formula for compounds in the center of the Periodic Table depends only on the nearest-neighbor separation d. It has the form B=1761${d}^{\mathrm{\ensuremath{-}}3.5}$ for B in GPa and d in A\r{}.

A Grain-boundary Defect Model for Instability/stability of a ZnO Varistor

Abstract: A defect model for the grain-boundary barrier has been proposed to explain the phenomena of voltage instability/stability of the ZnO varistor. The key element of the proposed model is the zinc interstitials which are present in the depletion layer as excess zinc, arising from the non-stoichiometric nature of ZnO. Both instability and stability have been described in terms of diffusion of these interstitials in the depletion layer, followed by chemical interactions with defects at the grain-boundary interface. Finally, a large body of experimental data is presented to indirectly validate the proposed defect model.

Influence of Dietary Calcium, Phosphorus, Zinc and Sodium Phytate Level on Cataract Incidence, Growth and Histopathology in Juvenile Chinook Salmon (Oncorhynchus tshawytscha)

Abstract: To determine the influence of wide variations in dietary levels of calcium, zinc and phytic acid (as sodium phytate) on growth and cataract incidence, juvenile chinook salmon held at 10-11 degrees C were fed daily to satiation for 105 d one of nine purified diets containing one of three levels (grams/kilogram) of calcium (averaged 48, 177, 502), zinc (averaged 005, 015, 039) and phytic acid (162, 646, 258) Diets were formulated to have a calcium-phosphorus ratio of close to unity when considering phosphorus sources other than sodium phytate High dietary phytic acid concentration (258 g/kg) depressed chinook salmon growth, food and protein conversion [protein efficiency ratio (PER)] and thyroid function, increased mortality, promoted cataract formation (zinc at 005 g/kg) and induced anomalies in pyloric cecal structure Calcium at 51 g/kg (or phosphorus) exacerbated the effects of high dietary phytate and low dietary zinc on cataract incidence Moreover, high dietary levels of calcium (48-51 g/kg) coupled with phosphorus significantly impaired the growth and appetite of low phytic acid (162 g/kg) groups and led to nephrocalcinosis in low and high phytic acid groups Plasma zinc levels were directly related to dietary zinc concentration and inversely related to dietary phytic acid level Calcium (51 g/kg) and/or phosphorus reduced zinc bioavailability when the diet concurrently contained 005 g zinc and 258 g of phytic acid per kilogram It is concluded that zinc is essential for normal eye development in juvenile chinook salmon Further, zinc deficiency could not be induced in chinook salmon fed diets with high ratios of calcium (or phosphorus) to zinc alone This required the simultaneous presence of a strong mineral (zinc)-binding agent

Allylzinc reagents additions in aqueous media

Abstract: Obtention d'alcools homoallyliques lorsque des halogenures d'allyle, zinc et aldehydes ou cetones sont soumis a une reaction sonochimique

Clinical Manifestations of Zinc Deficiency

Abstract: The essentiality of zinc for humans was recognized in the early 1960s. The causes of zinc deficiency include malnutrition, alcoholism, malabsorption, extensive burns, chronic debilitating disorders, chronic renal diseases, following uses of certain drugs such as penicillamine for Wilson's disease and diuretics in some cases, and genetic disorders such as acrodermatitis enteropathica and sickle cell disease. In pregnancy and during periods of growth the requirement of zinc is increased. The clinical manifestations in severe cases of zinc deficiency include bullous-pustular dermatitis, alopecia, diarrhea, emotional disorder, weight loss, intercurrent infections, hypogonadism in males; it is fatal if unrecognized and untreated. A moderate deficiency of zinc is characterized by growth retardation and delayed puberty in adolescents, hypogonadism in males, rough skin, poor appetite, mental lethargy, delayed wound healing, taste abnormalities, and abnormal dark adaptation. In mild cases of zinc deficiency in human subjects, we have observed oligospermia, slight weight loss, and hyperammonemia. Zinc is a growth factor. Its deficiency adversely affects growth in many animal species and humans. Inasmuch as zinc is needed for protein and DNA synthesis and for cell division, it is believed that the growth effect of zinc is related to its effect on protein synthesis. Whether or not zinc is required for the metabolism of somatomedin needs to be investigated in the future. Testicular functions are affected adversely as a result of zinc deficiency in both humans and experimental animals. This effect of zinc is at the end organ level; the hypothalamic-pituitary axis is intact in zinc-deficient subjects. Inasmuch as zinc is intimately involved in cell division, its deficiency may adversely affect testicular size and thus affect its functions. Zinc is required for the functions of several enzymes and whether or not it has an enzymatic role in steroidogenesis is not known at present. Thymopoeitin, a hormone needed for T-cell maturation, has also been shown to be zinc dependent. Zinc deficiency affects T-cell functions and chemotaxis adversely. Disorders of cell-mediated immune functions are commonly observed in patients with zinc deficiency. Zinc is beneficial for wound healing in zinc-deficient subjects. In certain zinc-deficient subjects, abnormal taste and abnormal dark adaptation have been noted to reverse with zinc supplementation.

Oral Iron, Dietary Ligands and Zinc Absorption

Abstract: The effect of iron on zinc absorption in humans was investigated by using 65Zn and whole-body counting after 2 wk. Increasing the molar ratio of ferrous iron (with ascorbic acid) to zinc from 1:1 to 2.5:1 did not affect absorption of zinc from water when given in a fasting state; 59 and 58% was absorbed, respectively. However, at an Fe:Zn ratio of 25:1, zinc absorption from water decreased significantly to 34%. When oral iron in the same ratio to zinc was given with a meal, no inhibitory effect was observed (25, 23 and 22%, respectively). Addition of the zinc ligand, histidine, to the water solution decreased the inhibitory effect of the higher dose of iron, resulting in a zinc absorption of 47%. Two weeks of iron preloading did not affect zinc absorption from water. The results demonstrate that when a multimineral supplement is taken on an empty stomach, excessive iron levels can negatively affect zinc absorption. Intake of the supplement with a meal or with a zinc ligand (such as histidine) may overcome this inhibitory effect.

Zinc-Modified Cyanoborohydride as a Selective Reducing Agent

Abstract: Proprietes reductrices du cyanotrihydroborate modifie par le zinc, (genere a partir du cyanotrihydroborate de sodium et du chlorure de zinc dans un rapport molaire 2/1) dans la reduction de composes carbonyles selectionnes, la reduction d'enamines, l'amination reductrice d'aldehydes et cetones, la methylation reductrice d'amines et la desoxygenation d'aldehydes et cetones via l'intermediaire de tosylhydrazones

Copper and zinc absorption in the rat: mechanism of mutual antagonism.

Abstract: The influence that copper and zinc exert on each other's absorption was studied by using the isolated, vascularly perfused rat-intestine system. In the first series of experiments, rats were fed for 1 wk one of nine diets, with different copper and zinc concentrations representing low, adequate and high dietary metal intakes. Copper concentrations were 1, 6 and 36 mg/kg diet and zinc concentrations were 5, 30 and 180 mg/kg. The small intestine was perfused with M199tissue culture medium containing 6 mg/L copper and 30 mg/L zinc. Neither metal was found to significantly alter the other's absorption. High dietary zinc increased metallothionein-bound copper but did not change the intracellular copper concentration. In the second series of experiments, the dietary copper and zinc concentrations were held at 6 mg/kg and 30 mg/kg, respectively, while the metal concentrations in the luminal perfusate were changed (from 1 to 36 mg/L and from 5 to 180 mg/L for copper and zinc, respective ly). The higher copper concentrations in the perfusate increased zinc accumulation in mucosal cells and decreased the zinc transferred to the portal perfusate at the highest luminal zinc concentration. These data indicate that a competition and/or inhibition of a pathway for zinc out of the mucosal cell occurs at high luminal copper con centrations. High luminal zinc concentrations in the perfusate decreased the copper concentration in the mucosal cell cytosol and the amount transferred to the portal effluent. These results taken together indicate that a competition and/or inhibition of copper or zinc uptake into intestinal cells occurs when the luminal concentration of the respective congener is very high. J. Nutr. 115: 159-166, 1985.

Clinical, endocrinologic, and biochemical effects of zinc deficiency.

Abstract: The requirement of zinc for humans was recognized in the early 1960s. The causes of zinc deficiency include malnutrition, alcoholism, malabsorption, extensive burns, chronic debilitating disorders, and chronic renal diseases; use of certain drugs such as penicillamine and, in some cases, diuretics; and genetic disorders such as acrodermatitis enteropathica and sickle cell disease. The requirement of zinc is increased in pregnancy and during growth. The clinical manifestations of severe zinc deficiency include bullous-pustular dermatitis, alopecia, diarrhea, emotional disorder, weight loss, intercurrent infections, and hypogonadism in males; zinc deficiency can be fatal if unrecognized and untreated. A moderate deficiency of zinc is characterized by growth retardation and delayed puberty in adolescents, hypogonadism in males, rough skin, poor appetite, mental lethargy, delayed wound healing, taste abnormalities, and abnormal dark adaptation. In mild cases of zinc deficiency in human subjects, we have observed oligospermia, slight weight loss, and hyperammonemia. Zinc is a growth factor. As a result of its deficiency, growth is affected adversely in many animal species and humans, probably because zinc is needed for protein and DNA synthesis and cell division. The effects of zinc and growth hormone on growth appear to be independent of each other in experimental animals. Whether zinc is required for the metabolism of somatomedin needs further investigation. Thyroid and adrenal functions do not appear to change as a result of zinc deficiency. Glucocorticoids may have an effect on zinc metabolism, although the clinical relevance of this effect is not known at present. In contrast, testicular function is affected adversely as a result of zinc deficiency in both humans and experimental animals. The effect appears to be a direct one since the hypothalamic-pituitary axis is intact, and may relate to the reduction in testicular size as a result of the need for zinc in cell division. In addition, zinc is required for the function of several testicular enzymes, although a specific role in steroidogenesis has not been identified. Zinc appears to have a role in the modulation of prolactin secretion, in the secretion and action of insulin, and in the production and biologic effects of thymic hormones. It is clear that the endocrine consequences of zinc deficiency are multiple, and that continued investigation should provide additional pathophysiologic and therapeutic insights.

Zinc Oxide Films for Acoustoelectric Device Applications

Abstract: Avantages des dispositifs acoustoelectriques a ondes acoustiques de surface utilisant une couche piezoelectrique de ZnO deposee sur un substrat semiconducteur

Dissolved zinc in rivers

Abstract: Reliable measurements of the concentrations of dissolved trace metals in rivers are needed for calculating oceanic chemical mass balances, understanding continental weathering and freshwater chemistry, and evaluating anthropogenic chemical perturbations. For dissolved zinc, it has been suggested1 that typical river concentrations are as high as 450 nmol kg−1. However, it has also been proposed2 that most published values are incorrect and the true value of dissolved zinc may be 2 orders of magnitude lower. Because zinc is one of the most commonly used metals in the industrial world, the sampling and analysis of this element in natural waters is particularly prone to contamination2. We present here the dissolved zinc concentrations from various rivers draining both pristine and industrially influenced environments. These samples were collected and analysed by methods that have yielded reliable oceanic data for other metals3. The data indicate that in relatively undisturbed systems dissolved zinc concentrations are typically only 10−9–10−8 mol kg−1, with some dependence of concentration on pH. In industrially influenced river systems, however, zinc concentrations can be 1–2 orders of magnitude higher.

Zinc utilization in young men fed adequate and low zinc intakes.

Abstract: Zinc absorption and balances were measured in six young men who were confined while participating in a 75-d metabolic study. A diet of conventional food providing either 16.5 or 5.5 mg Zn/d was fed. Apparent absorption of zinc was calculated from the zinc balance data and from the absorption of a zinc stable isotope added to the diet. The apparent zinc absorption calculated from the isotope data was about 25% when 16.5 mg zinc was fed; it increased to about 53 and 49% after 13 and 42 d, respectively, when 5.5 mg zinc was fed. Total zinc absorption fell from 4.1 mg/d to 2.7-2.9 mg/d during the low zinc period, however. This zinc absorption was sufficient to maintain crude zinc balances in five of the six subjects. Neither serum nor urinary zinc levels changed significantly during the period of feeding low levels of zinc. It appears that zinc absorption readily responds to changes in dietary zinc and that an intake of 5.5 mg Zn/d for about 8 wk does not cause serum or urinary zinc level to fall.

Zinc alkaline battery

Abstract: This invention uses as the anode active material a zinc alloy containing Ni, at least one element selected from In, Pb, Ga and Cd and, optionally further, one element selected from Al, Mg, Ca, Ba and Sr for the anode of a conventional zinc-alkaline battery which employs zinc as the anode active material, aqueous alkaline solution as the electrolyte, and manganese dioxide, silver oxide, oxygen and so forth as the cathode active material. The use of such zinc alloy permits the reduction of the amount of mercury to be used for amalgamation of the anode zinc surface which is made for the purpose of corrosion inhibition, thereby enabling the provision of a low-pollution zinc-alkaline battery.

Maternal zinc and intrauterine growth retardation

Abstract: The levels of zinc in plasma, erythrocytes, polymorphonuclear (PMN) and mononuclear (MN) white cells were measured after delivery in women giving birth to appropriate-for-gestational-age (AGA) babies (group I mothers), or small-for-gestational-age (SGA) babies (group II mothers) and in non-pregnant controls. Mean maternal plasma zinc and albumin levels 24-48 h after delivery were lower than in controls, but PMN and MN zinc levels were unchanged. PMN zinc levels were lower than those of MN cells. PMN and MN zinc levels were significantly lower in group II mothers than in group I, irrespective of smoking habits. There were no racial differences in peripheral white cell zinc levels. PMN, and to a lesser degree MN, zinc levels were lower in smoking than in non-smoking mothers. Erythrocyte zinc did not correlate with other zinc measurements nor with the size of the babies. Fetal erythrocyte zinc levels were one-third of maternal levels. A combination of smoking and/or low PMN zinc levels selects 85% of mothers having small-for-gestational-age babies.

Studies of reactions of atomic and diatomic chromium, manganese, iron, cobalt, nickel, copper, and zinc with molecular water at 15 K

Abstract: Formation de molecules HMOH (M=Cr, Mn, Fe, CO, Ni, Cu et Zn) qui photolysees conduisent a HMn 2 OH, HMnOMnH, HFeOFeH, Fe(OH) 2 HFe 2 OH et H x Cr(OH) 2 . Le cuivre et le zinc donnent CuOH et ZnOH

Electroless deposition of cadmium stannate, zinc oxide, and aluminum‐doped zinc oxide films

Abstract: Transparent conducting films of cadmium stannate (Cd2SnO4), zinc oxide, and aluminum‐doped zinc oxide have been made by a simple, economical electroless deposition technique. The as‐deposited films of cadmium stannate have a 75% transmittance in the visible, 48% reflectance in the IR, and a band gap of 2.7 eV. Its resistivity is ∼10−1 Ω cm. Vacuum annealing changes the transmittance in the visible range to 82%, the IR reflectance to 62%, and the band gap to 3.1 eV. The corresponding values for the hydrogen‐annealed films are 87%, 76%, and 3.2 eV. Annealing lowers the resistivity of the films to ∼10−2 and ∼10−3 Ω cm for vacuum and hydrogen‐annealed films, respectively. The undoped zinc oxide films have transmittance in the visible and reflectance in the IR of 80 and 67% respectively. Aluminum doping increases the transmittance to 88% and reflectance to 83%. The optical band gap of undoped and aluminum‐doped zinc oxide films are found to be 3.40 and 3.98 eV, respectively. The resistivity is 1.20×10−2 and 6....

Oral hygiene compositions

Abstract: An oral hygiene composition containing an effective concentration of a pharmaceutically acceptable fluoride salt, a pharmaceutically acceptable zinc salt, a specific buffering agent, a suitable vehicle and having a pH of from about 3.5 to 6.0.

Catalytic formation of hydrogen and carbon-carbon bonds on illuminated zinc sulfide generated from zinc dithiolenes

Abstract: L'irradiation UV du complexe bis(cis-dicyano-1,2 ethylenedithiolate-1,2) Zinc bis(tetrabutylammonium) dans le THF ou le dihydro-2,5 furanne aqueux conduit a n-Zn S qui photocatalyse le degagement d'hydrogene (φ≥0,1) couple a une dehydrodimerisation de l'ether cyclique. Mecanisme. Cinetique

Pure amino acid chelates

Abstract: Pure amino acid chelates and a method of their production are disclosed. The amino acid chelates are free of contaminating inorganic anions. The chelate consists of a metal ion comprising iron, zinc, manganese, magnesium, copper, calcium and mixtures thereof. The metal ion is chelated to one or more ligands comprising alpha amino acids, protein hydrolysates, polypeptides, dipeptides, and combinations thereof. A novel process is disclosed wherein the amino acid ligand is brought into reactive contact with a divalent metal ion in an environment which is completely anion free but otherwise conducive to the interaction between the amino acid ligand and the metal ion, with the formation of an amino acid chelate in pure form or, at least, which can readily be recovered from the reactive environment in pure form.