Accumulation Of Fluorine Research Articles

Geographical environmental characteristics of endemic fluorosis in China

Endemic fluorosis is given rise to by human intake of excess fluorine from environment by way of food chain. In China it is one of the extensively prevalent endemic diseases and its distribution shows clearly regional characteristics. In macroscopic sight, three large fluorosis zones may be divided: (1) The arid and semi-arid plains in the north of China. These regions have a dry climate, making fluorine accumulation in the Quaternary deposits. Thus, the drinking water with high content of fluorine is the main cause of the disease formation. (2) The Yunnan-Guizhou Plateau. In the region, rocks and soils rich in fluorine bring about fluorine excess in crop food. This plays an important role in the disease formation. (3) Southeast hills. The hot spring with high content of fluorine leads to fluorosis.

Chemistry of fluorine in the oxidation of silicon

The chemical environment of fluorine in the oxide layer of metal-oxide-semiconductor (MOS) structures has been examined by surface analytical spectroscopies. HF treatment of Si(100) results in subsurface SiF formation. Upon oxidation, oxyfluoride moieties are formed with a significant accumulation of fluorine throughout the oxide layer. These changes are correlated to the electrical integrity of MOS interfaces by performing Fowler–Nordheim electron injection studies.

Tissue distribution of [18F]-5-fluorouracil in mice: effects of route of administration, strain, tumour and dose

In a study investigating the usefulness of 5-fluorouracil labelled with fluorine 18 [( 18F]-5-FU) in cancer chemotherapy, the tissue distribution of the radiolabel was determined in mice at 2, 4 and 6 h after administration by varying several parameters such as the mode of administration, the strain of mouse, the presence of a tumour and the total dose of 5-FU. The tissue distribution of fluorine 18 after i.p. injection pointed to an altered behaviour of the drug and/or its metabolites when compared with values obtained after i.v. injection, but no difference was found in the accumulation of radiolabel in the tumour. A comparison of non-tumour-bearing BALB/c and C57Bl/6 mice revealed that the latter showed a higher radiolabel accumulation of the drug and its metabolites in the liver, kidney, intestines and coecum (P less than 0.05 at 2 and 4 h). In tumour-bearing mice, especially at 2 h, the tissue accumulation of radiolabel was found to be significantly higher than in non-tumour-bearing controls (in BALB/c mice bearing colon 26 carcinoma, P less than 0.05 for all tissues; in C57Bl/6 mice bearing colon 38 carcinoma, P less than 0.05 for the blood, lung, liver, kidney, large intestines, coecum and muscle). Finally, a comparison of injections of a tracer dose of [18F]-5-FU (2.5 mg/kg) vs a therapeutic dose (100 mg/kg) revealed only small differences in the accumulation of fluorine 18 in the liver and kidney.

Properties of TiSi2 as an encroachment barrier for the growth of selective tungsten on silicon

Selective growth of chemical-vapor deposited selective tungsten, on thermally grown titanium silicide thin films, on silicon substrates, has been characterized. The nucleation of selective tungsten is found to be strongly affected by the surface chemical composition of the silicide. A thin layer of titanium nitride, formed on the silicide surface during the silicidation of sputtered titanium in nitrogen ambient, does not allow selective tungsten nucleation and has to be chemically removed to observe growth of the tungsten film. Localized titanium oxide regions on the silicide surface lead to adhesion problems between tungsten film and the silicide underlayer resulting in tungsten film blistering and bubbles formation. The regions of silicide where these bubbles form show accumulation of fluorine from the WF6 reduction at the interface. In regions of good adhesion and normal growth characteristics, no titanium oxide was found, almost all the silicide was consumed during the growth of selective tungsten and no fluorine accumulation at the interface was observed. These results indicate that it is possible to grow selective tungsten on titanium silicide barrier over silicon substrate provided that the surface of silicide is free of any titanium oxide or nitride layers. Under such conditions, the silicide layer acts as a sacrificial barrier allowing selective tungsten growth without resulting in any silicon consumption or encroachment of tungsten into the silicon substrate.

TiSi2thickness limitations for use with shallow junctions and SWAMI or LOCOS isolation

We have examined the impact of TiSi <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> formation on the properties of shallow n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> junctions (0.17-0.20 µm) in Si. The deposited Ti thickness varied from 300 to 1000 Å. The p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> junctions developed high leakage currents after a reaction with Ti of initial thickness greater than 700 Å while the n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> junctions were not degraded. In these studies LOCOS isolation was used and the TiSi <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> was formed away from the island edges. Additional experiments were performed on n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> diodes using SWAMI isolation with the TiSi <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> formed right up to the edges of the isolation. From step-height, spreading resistance, and RBS measurements, it was found that the thickness of TiSi <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> formed on n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> Si was less than on p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> Si for a given initial Ti thickness. The amount of electrically active dopant remaining in the substrates was seen to decrease with increasing Ti thickness. The result was supported by SIMS measurements, which also showed an accumulation of atomic fluorine at the TiSi <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> interface (on p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> diodes only). Cross-sectional transmission electron microscopy was used to examine the silicide morphology and interface planarity.

Chemical, sorptive and morphological properties of montmorillonite treated with ammonium bifluoride (NH4HF2) solutions

AbstractThe fluorination of montmorillonite by aqueous ammonium bifluoride solution (NH4HF2) has been investigated by chemical, sorptive, porosimetric and electron microscopic methods. Changes in the chemical composition of the montmorillonite during the fluorination were compared both in the crystal surface and in the bulk sample. The accumulation of fluorine was distinctly zonal, being present mainly in the surface layers. The electron microscope studies showed that the 300–400 nm thick macrodomains in the initial montmorillonite were cracked into small microdomains 20–30 nm in thickness, this resulting from disruption in the continuity of the octahedral sheets. These distinct changes in morphology of the montmorillonite aggregates particularly influenced the porosity and sorptive properties.

The interface of plasma-anodized Hg1−xCdxTe

The process for forming plasma-anodized oxide on Hg1−xCdxTe with x = 0.215 and 0.290 and the properties of the interface are studied. The results of Auger electron spectroscopy and x-ray photoelectron spectroscopy surface analytical characterization and the electrical interface characterization are compared with respective data on the interface between Hg1−xCdxTe and its solution anodized native oxide. The plasma oxide exhibits a decreasing gradient of oxygen and an increasing gradient of unoxidized tellurium from the surface towards the bulk semiconductor. An accumulation of fluorine at the interface unique to the plasma oxide is observed. Metal-Insulator-Semiconductor (MIS) devices with the plasma-anodized interface have a relatively low concentration of positive fixed surface charge density, (1–3)×1011 cm−2, and fast surface state density per unit band gap of about 2×1011 cm−2 eV−1, measured at 77 K. The hysteresis in the capacitance-voltage characteristics of the MIS devices is negligible, indicating the near absence of slow-trapping effects which have been observed in anodic solution oxides. Photoconductors passivated with plasma oxide exhibit good responsivity and detectivity, indicating small surface recombination velocity and small interface trapping. A significant advantage of the plasma oxide is the excellent thermal stability of the interface. Devices such as MIS capacitors and photoconductors may be annealed in vacuum up to 95 °C for prolonged periods while retaining their properties.

Joint action of HF and NO 2 on growth, fluorine accumulation, and leaf resistance in marcross sweet corn

Sweet corn ( Zea mays L. cv. “Marcross”) was exposed continuously to HF (0.5 or 1.5 μg m −3) with or without intermittent exposure to NO 2 (1140 or 2280 μ m −3). Changes in foliar F accumulation, HF-induced injury symptoms, plant dry weight, leaf area, and leaf resistances were monitored. Fluorine accumulation was reduced when NO 2 was combined with HF at 0.5 μg F m −3, but not at 1.5 μg F m −3. Typical F-injury symptoms were found only on plants exposed to 1.5 μg HF m −3. Plants exposed to 1.5 μg HF m −3 and the higher NO 2 concentration developed fewer lesions and lesion development was delayed by one or two days in comparison to plants exposed to HF only. At the lower NO 2 concentration there were no differences in lesion severity or development. Leaf resistances of plants exposed to 1.5 μg HF m −3 were generally lower than controls, but were generally higher in plants exposed to HF and NO 2 or only NO 2. These differences in leaf resistance may partially explain the interactive effects of HF and NO 2 on plant growth and F accumulation.

Air pollutant uptake by xerophytic vegetation: Fluoride

Drought resistance has been found to correlate in some species with resistance to air pollutants. In xerophytic species, drought resistance is often associated with anatomical and physiological leaf characteristics, which control plant water loss. The characteristic path of pollutant uptake in these species could be different from that reported as widespread among mesophytic plants. Measurements of fluoride content in intact and washed plant leaves, leaf water potentials, and exposure to pollutant carrying winds were performed in the vicinity of an aluminum smelter. Electronic fluorine specific microprobe measurements were made to localize fluoride in leaf tissues. The results indicate that fluoride uptake by these species consists in a deposition-adsorption upon the external leaf surface, followed by a slow diffusion to inner tissues which is regulated by the water potential at the epidermis and cuticle. The absence of fluorine accumulation in substomatic tissues suggests that the uptake of gaseous fractions of fumes through stomata would be relatively unimportant when quantitatively compared to the above mechanism.

Influence du fluor sur la composition minerale d'aiguilles polluees de sapin ( Abies alba Mill.)

Chemical composition of fir needles is modified by elevated fluorine accumulation. Our results indicate that fluoride pollution tends to reduce the concentration of Mg and Mn and to increase that of Ca and F. They also indicate that fluorine level has no consistent effect on levels of major nutrient elements, e.g. N, P and K. Nevertheless, from an internal fluorine accumulation of 400 ppm, depletion of Mg and Mn and higher fluorine level had no significant effect on levels of the remaining elements. Moreover, a very similar depletion of Mg and Mn with fluorine accumulation is observed and a positive correlation may be found between these two elements.

ふっ化物による環境汚染に関する生物学的研究 Ｉ 植物に及ぼす気中のふっ化物の影響

In this report, gladiolus (Gladiolus gandavensis), mandarin (Citrus Unshiu), taro (Colocasia antiquorum), Japan-ceder (Cryptomeria japonica) and rice (Oryza sativa) were used as plant indicators of air-pollution by fluoride. The sensitivity of these plants against atmospheric fluoride was found to be taro>gladiolus>Japan-ceder>mandarin. On the other hand, the pool size of fluorine accumulation in plant leaves was suggested to be Japan-ceder>mandarin>gladiolus>taro. The calcium contents in the leaves of mandarin and gladiolus were 4.16% and 1.04% as average, respectively. The ratio of Ca/Si in the leaves of mandarin and gladiolus was 32.7 and 4.38 as average, respectively. The contents of calcium and silica in the leaves in plants were suggested to be concerned with the sensitivity of plants against atmospheric fluoride. Accumulation of fluorine in unhulled rice was associated with fluorine content in the rice bran, but was not associated with that in the polished rice. Their plant indicators were demonstrated as an applicable method to detect atmospheric fluoride.

The Accumulation of Fluorine by Plants

The accumulation and distribution of fluorine (F) in -plant leaves have been studied to better understand the response of plants to concentrations of atmospheric fluoride (F) that are similar to those found in urban or industrial areas. The results indicate that F from the air can be adsorbed to the surface of leaves as well as accumulated internally and that F in leaves can be translocated outward to the surface as well as upward to the tips. F injury and accumulation can be induced in any desired location on a gladiolus blade by restricting gas exchange of the blade, indicating that all parts of a blade are sensitive to F-induced injury. It is, therefore, suggested that the wide differences often found between plant species and varieties with respect to both susceptibility to injury and degree of F accumulation may be explained by differences in the means of accumulation, trans-location, and distribution of F. F remains in a soluble form in plant leaves and maintains the chemical properties of free, ino...

The Use of Tail Bone Biopsy for Studying Skeletal Deposition of Fluorine in Cattle

SUMMARY A simple, rapid and safe method of tail bone biopsy in cattle is described. This technique provides a reasonably accurate method for assessing the skeletal fluorine level and has proved a useful means of measuring accumulation of bone fluorine for both diagnostic and experimental purposes.

Placental transfer of fluorine in the human fetus.

Samples of the blood from pregnant women shortly before delivery, placentas at full term and cord blood, were analyzed for fluorine. All subjects drank from the same water source which contained about 0.55 ppm fluorine. The results suggest that the placenta plays an active role in accumulation of fluorine and its transfer to the fetus.

Effect of fluorine on thyroidal iodine metabolism in hyperthyroidism.

Prolonged administration of a daily dose of 5-10 mg. of fluoride to patients with hyperthyroidism may cause clinical improvement together with a significant fall in the level of plasma protein-bound iodine and a reduction in the basal metabolic rate. Studies with radioactive fluorine failed to demonstrate any important accumulation of fluorine within the thyroid in vivo. Thyroidal, blood and urinary radioiodine studies suggest that fluorine inhibits the thyroid iodide-concentrating mechanism. Fluorine does not impair the capacity of the gland to synthesize thyroid hormone when there is an abundance of iodide in the blood. However, inhibition of the thyroidal concentrating capacity when the total iodide pool is low will impose a critical limitation of hormonal synthesis, and may explain the therapeutic effect.

The Distribution and Storage of Fluorine in the Tissues of the Laying Hen

THE ingestion of small quantities of fluorides with the diet causes an accumulation of fluorine in the tissues of the animal and ultimately chronic toxicosis. Sonntag (1916) increased the F content of the bones of dogs from a value below 0.3 percent in normal animals to 1.73 percent in NaF fed animals. Brandl and Tappeiner (1891) examined microscopically the bones of a young growing dog and found crystals deposited which resembled the crystalline fluoride CaF2. Bethke, et al (1929), and Kick (1932) have shown the increased F storage in the bones of pigs following F intake as NaF or rock phosphate. Brandl and Tappeiner (1891), as well as Trebitsch (1927), further demonstrated the deposition of F in the tissues of animals fed small amounts of fluorine in the diet. The work of Tolle and Maynard (1931) upon rats showed a relatively large increase in bone ash from normal to NaF .