Addition Of NaF Research Articles

Preparation and high temperature oxidation resistance of microarc oxidation ceramic coatings formed on Ti2AlNb alloy

Microarc oxidation (MAO) was used to produce oxide ceramic coatings on Ti2AlNb alloy. The influences of NaOH and NaF additives in the electrolyte on microstructure and high-temperature oxidation resistance of MAO ceramic coatings were investigated. MAO ceramic coatings formed on Ti2AlNb alloy exhibit a volcanic-like porous structure, and consist of Al2TiO5, R-TiO2, γ-Al2O3 and small amounts of α-Al2O3, Nb2O5. NaOH additive in the electrolyte enhances the densification of ceramic coatings and the relative content of Al2TiO5. NaF additive in the electrolyte not only increases the thickness of coatings, but also promotes the formation of Al2TiO5. In the case of static oxidation at 800°C for 100h, MAO coatings improve high temperature oxidation resistance of Ti2AlNb alloy. The oxidized products after thermal exposure to 800°C for 100h in air exhibit a multiple-layered oxide structure, and are main composed of R-TiO2, γ-Al2O3 and Al2TiO5.

Hydrosilicate liquids in the system Na2O-SiO2-H2O with NaF, NaCl and Ta: Evaluation of their role in ore and mineral formation at high T and P

Consideration of the existence of hydrosilicate liquids (HSL) in nature can help in understanding the accumulation and transport of some mineral- and ore-forming components at the transition from magmas to hydrothermal fluids. We studied the experimental formation of HSL using a base system Na2O-SiO2-H2O with addition of NaF, NaCl and metallic Ta. The interaction between quartz and aqueous solution, performed at 1.5 kbar and 600°C and followed either by cooling or by quench, showed that the formation of HSL occurred when initial Na2O exceeded 2 wt %. Neither NaF nor NaCl have a significant effect on the formation of HSL. The HSL concentrates F, whereas Cl partitions into the aqueous fluid. With addition of Ta to the system, the HSL becomes metal-enriched. Natural analogs of experimental HSL can be found among “melt/fluid” inclusions entrapped in quartz and other minerals of miaroles in granite pegmatites and raremetal granites. The HSL is a novel medium enabling extreme concentrations of lithophile ore metals at the magmatic-hydrothermal transition.

Surface Roughness Changes and Corrosion on Nickel Titanium Orthodontic Wires Compared to Stainless Steel Wires in Various Artificial Salivas

Abstract Nickel titanium shape memory alloy and stainless steel orthodontic wires were exposed to three different artificial saliva solutions which are modified Fusayama, modified Fusayama with 1g/l NaF addition and modified Fusayama with 1.7 % H3PO4 addition. Under conditions similar to oral cavity temperature, corrosion behaviours were observed by using weight loss method and by macro surface photographic observations. Also, surface roughness of wires were investigated and compared. Consequently, it was determined that corrosion rates of all NiTi wires exposed to the modified Fusayama solutions with NaF addition are higher because of galvanic interaction of NiTi and hydrogen embrittlement of titanium. Also, surface roughness of NiTi wires were increased in modified Fusayama solution with NaF addition.

The effect of sodium fluoride preservative and storage temperature on the stability of cocaine in horse blood, sheep vitreous and deer muscle

The in vitro stability of cocaine in horse blood, sheep vitreous humour (VH) and homogenised deer muscle is described. The stability of cocaine in horse blood was of interest because many toxicology laboratories utilise horse blood for the preparation of calibration and check standards and the latter are typically stored during routine use. The storage stability of cocaine in human VH and muscle has not been previously reported. In the absence of blank human VH and muscle, cocaine stability under varying conditions was demonstrated in animal tissues. Blood and VH were stored with and without addition of NaF at room temperature (RT), 4°C and -18°C for 84 days. Muscle homogenates were prepared in water, water/2% NaF, and phosphate buffer (pH 6.0)/2% NaF, and stored for 31 days at RT, 4°C and -18°C. Cocaine stability in human muscle obtained from cocaine positive forensic cases was assessed following storage at -18°C for 13 months. Cocaine and benzoylecgonine (BZE) were extracted using SPE and quantified by GC-MS/MS. Cocaine was stable for 7 days in refrigerated (4°C) horse blood fortified with 1 and 2% NaF. In the absence of NaF, cocaine was not detectable by day 7 in blood stored at RT and 4°C and had declined by 81% following storage at -18°C. At 4°C the rate of cocaine degradation in blood preserved with 2% NaF was significantly slower than with 1% NaF. The stability of cocaine in horse blood appeared to be less than that reported for human blood, probably attributable to the presence of carboxylesterase in horse plasma. Cocaine stored in VH at -18°C was essentially stable for the study period whereas at 4°C concentrations decreased by >50% in preserved and unpreserved VH stored for longer than 14 days. Fluoride did not significantly affect cocaine stability in VH. The stability of cocaine in muscle tissue homogenates significantly exceeded that in blood and VH at every temperature. In preserved and unpreserved samples stored at 4°C and below, cocaine loss did not exceed 2%. The increased stability of cocaine in muscle was attributed to the low initial pH of post-mortem muscle. In tissue from one human case stored for 13 months at -18°C the muscle cocaine concentration declined by only 15% (range: 5-22%). These findings promote the use of human muscle as a toxicological specimen in which cocaine may be detected for longer compared with blood or VH.

Effects of nucleation agents on the preparation of transparent glass–ceramics

Formation of transparent glass–ceramic in the system MgO–SiO2–Al2O3–K2O–B2O3–F with and without addition of LiF and NaF has been investigated. Crystallization of glass-sample was conducted by controlled thermal heat-treatment, at determined nucleation and crystallization temperatures. In this regard, the effects of addition of LiF and NaF were investigated on the crystallization behavior and transparency of the samples. Low transmission (less than 80% at 600 nm) was observed in the basic composition (K). The addition of NaF and LiF caused more intense phase separation in the system. The results indicated that the glass–ceramic can remain transparent if fine grains with nano size are precipitated but will turn into opaque when large grains appear, because of the difference in the refractive index between glass and precipitated crystals.

Synthesis of visible light-driven Eu, N co-doped TiO2 and the mechanism of the degradation of salicylic acid

Europium and nitrogen co-doped TiO2 was successfully synthesized by the precipitation–peptization method. The structure and properties of the catalysts were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectra. The photocatalytic efficiency was evaluated by monitoring the photocatalytic degradation of salicylic acid under visible light irradiation. It was verified that TiO2 co-doped with nitrogen and 1% europium showed the highest photocatalytic activity. The adsorption isotherms were obtained by measuring the salicylic acid concentration before and after the dark adsorption at different original solution concentrations. The results illustrated that the doping of Eu was beneficial to the adsorption of salicylic acid. The probable degradation mechanism of salicylic acid was examined by the addition of NaF, Na2S2O3, and K2S2O8 as the probe molecules. It was verified that salicylic acid was first adsorbed on the surface of the catalysts, followed by the degradation by the photogenerated holes (h vb + ).

Sodium fluoride induces apoptosis in mouse embryonic stem cells through ROS-dependent and caspase- and JNK-mediated pathways

Sodium fluoride (NaF) is used as a source of fluoride ions in diverse applications. Fluoride salt is an effective prophylactic for dental caries and is an essential element required for bone health. However, fluoride is known to cause cytotoxicity in a concentration-dependent manner. Further, no information is available on the effects of NaF on mouse embryonic stem cells (mESCs). We investigated the mode of cell death induced by NaF and the mechanisms involved. NaF treatment greater than 1mM reduced viability and DNA synthesis in mESCs and induced cell cycle arrest in the G2/M phase. The addition of NaF induced cell death mainly by apoptosis rather than necrosis. Catalase (CAT) treatment significantly inhibited the NaF-mediated cell death and also suppressed the NaF-mediated increase in phospho-c-Jun N-terminal kinase (p-JNK) levels. Pre-treatment with SP600125 or z-VAD-fmk significantly attenuated the NaF-mediated reduction in cell viability. In contrast, intracellular free calcium chelator, but not of sodium or calcium ion channel blockers, facilitated NaF-induced toxicity in the cells. A JNK specific inhibitor (SP600125) prevented the NaF-induced increase in growth arrest and the DNA damage-inducible protein 45α. Further, NaF-mediated loss of mitochondrial membrane potential was apparently inhibited by pifithrin-α or CAT inhibitor. These findings suggest that NaF affects viability of mESCs in a concentration-dependent manner, where more than 1mM NaF causes apoptosis through hydroxyl radical-dependent and caspase- and JNK-mediated pathways.

Influence of fluoride-containing acidic artificial saliva on the mechanical properties of Nickel-Titanium orthodontics wires

This study aimed to investigate the influence of fluoride and an acidic environment on the mechanical properties of NiTi orthodontic wires (NiTiW) in artificial saliva. A prospective laboratory investigation. Department of Stomatology, First Affiliated Hospital, Zhejiang University, Hangzhou, China. Commercial, round 0.016-inch NiTiW were immersed in 0% or 0.05% Natrium-Fluoride-containing artificial saliva at a pH of 4 or 6 for one or three days, respectively. NiTiW were examined with a three-point bending test, Vickers' microhardness tests and surface morphology observation (SEM). A pH of 4 increased microhardness and decreased the three-point bending strength significantly (P≤0.05), whereas immersion time and fluoride concentration had no significant influence on the microhardness or on the three-point bending strength (P>0.05). When examining the test group NiTiWs after three days of immersion at a pH of 4 the SEM revealed a rough surface morphology, a damaged oxide layer and signs of corrosion. The most influential factor for decreasing the unloading force and increasing the hardness seems to be the pH value, whereas immersion time and NaF addition do not have a major influence.

The effect of sodium fluoride preservative and storage temperature on the stability of 6-acetylmorphine in horse blood, sheep vitreous and deer muscle

This study examined the in vitro stability of 6-acetylmorphine (6AM) in horse blood, sheep vitreous humour (VH) and homogenised deer muscle stored under different storage conditions. The stability of 6AM in horse blood is of interest because many toxicological laboratories utilise this matrix for the preparation of blood calibration and check standards and the latter are typically stored during routine use. Data on the storage stability of 6AM in human VH is extremely limited and no data has been reported in muscle. In the absence of human samples, 6AM stability was demonstrated in sheep vitreous and deer muscle. Blood and VH were stored with and without NaF at room temperature (RT), 4 and -18°C for 84 days. Muscle tissue homogenates were prepared in water with and without NaF and also in phosphate buffer (pH 6.0) containing NaF. Homogenates were stored for 31 days at RT, 4 and -18°C. Morphine and 6AM were extracted using SPE and quantified by GC-ion trap-MS/MS. In the absence of NaF, 6AM could not be detected after 7 and 14 days in blood stored at RT and 4°C, respectively. Although at -18°C 6AM was stable for 7 days (12% loss), only 54% was detected by day 84. The addition of NaF to horse blood increased 6AM stability substantially at every temperature. Further, the rate of degradation was found to be significantly slower in blood preserved with 2% NaF compared with 1% NaF (p=.05). 6AM was stable for the study period in preserved blood (1 and 2% NaF) stored at -18°C. For laboratories utilising horse blood in the preparation of standards, preservation with 1% NaF (minimum) and storage at -18°C is recommended. The addition of NaF to VH was essential for 6AM stability. Irrespective of temperature substantial losses (≥ 42%) were observed in unpreserved sheep VH by day 7. In preserved VH the concentration declined by only 22% on day 7 following storage at RT and no loss observed in VH stored at 4 and -18°C at the same time. In muscle, 6AM was stable for 7 days in preserved samples stored at RT and in all samples stored at 4°C and below. The addition of NaF increased the stability of 6AM substantially in muscle. The increased stability of 6AM in VH and muscle preserved with fluoride was attributed to inhibition of bacterial action and the subsequent reduction in the rate of putrefaction of these tissues.

Influence of sodium fluoride (NaF) on the crystallization and spectral properties of l-tyrosine

l-Tyrosine (C 9H 11NO 3) is an essential amino acid in living organisms. It is also a building unit in protein, takes part in bio-synthesis of hormones, neurotransmitters, pigments and one of the organic chemical constituents of urinary stones. l-Tyrosine has been crystallized in silica gel by double diffusion technique with and without the addition of NaF. The crystals had rosette-like shape. In case of fluoride addition, two types of crystals have formed: rosette like crystallites, at the gel–solution interface and reticulate type crystallites beneath the interface. XRD results confirmed that both the products are of l-tyrosine with identical crystal structures. Crystal structure, morphology, thermal and spectral properties are analyzed using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric and differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FTIR) and UV–vis transmittance studies. The TG–DTA results suggest that the thermal stability of l-tyrosine has markedly improved due to fluoride doping. Optical band gap energy of NaF grown l-tyrosine crystallite is estimated as 4.28 eV. Second harmonic generation efficiency test indicates that l-tyrosine crystals can be used for application in nonlinear optical devices.

A Study of the Viscous Properties with NaF Additions in the CaO-SiO2-12 mass pct Na2O Based Slags

The viscous behavior of the CaO-SiO2-12 mass pct Na2O based slag system with various concentrations of NaF has been studied using the rotating spindle method. NaF additions decreased the viscosity by interacting with bridged oxygens in the complex silicates and depolymerizing the network structure of the molten slag. NaF was particularly effective at lowering the viscosity in small amounts, but beyond 8 mass pct NaF, the effect was not as pronounced. A comparison between additions of NaF and CaF2 revealed NaF to be more effective at decreasing the viscosity for 1523 K and 1573 K (1250 °C and 1300 °C). From the slopes of the Arrhenius relationship for viscosity, the activation energy of viscous flow was found to be between 128 kJ/mol to 115 kJ/mol, which were lower than the values for the same amount of CaF2 additions. Both a temperature effect and a compositional effect on the molten slag structure and subsequently the viscous behavior were observed. The Fourier transformed infrared (FTIR) spectra taken for the CaO-SiO2-12 mass pct Na2O-8 mass pct NaF slag samples quenched from 1623 K to 1773 K (1350 °C to 1500 °C) revealed that the temperature effect on the viscosity was observed at temperatures below 1673 K (1400 °C).

Process intensification of heterogeneous photocatalysis with static mixer: Enhanced mass transfer of reactive species

The process intensification (PI) of heterogeneous photocatalysis using the Kenics static mixer was investigated and its mechanism was proposed. Three model compounds (phenol, Cr(VI), and acid orange 7 (AO7)) with different photocatalytic reaction mechanisms were selected. The use of the Kenics static mixer increased the degradation rate of phenol from 20% to 150%, but appeared to have no effect on the photodegradation of Cr(VI) and AO7. However, with the addition of formic acid and NaF to the Cr(VI) and AO7 systems, respectively, the reaction mechanism shifted from a surface-mediated reaction to a radical-mediated reaction, and the photoreduction of Cr(VI) and photo-oxidation of AO7 using the Kenics static mixer exhibited higher reaction rates. In addition, the results of experiments with the terephthalic acid (TA) fluorescence probe indicated that the Kenics static mixer increased the yield of hydroxyl radicals. Based on the reaction mechanisms, we propose that the Kenics static mixer played a role in heterogeneous photocatalysis by creating intense mixing and increasing the interfacial mass transfer, which resulted in the enhanced mobility of reactive radicals from the catalyst surface or boundary layer to the solution. This approach intensified the heterogeneous photocatalysis process by enhancing the mass transfer of the reactive species rather than the reactant substrate, provided an alternative to the PI of heterogeneous photocatalysis, and allowed for easier engineering applications.

Preparation of floral mesoporous SAPO-34 with the aid of fluoride ion

A novel floral mesoporous SAPO-34 was synthesized via conventional hydrothermal method in the presence of NaF with F/Si = 0.02–0.2. X-ray diffraction (XRD) analysis shows that the crystallinity of SAPO-34 increases with the increasing F/Si ratio and reaches to the best at F/Si = 0.1. Further increasing of F/Si ratio leads to the decrease of the crystallinity and the ultimate phase transformation to SAPO-5. Scanning electron microscopy (SEM) analysis shows that the addition of NaF leads to the formation of floral SAPO-34 while the addition of other salts including NH 4F, NH 4Cl and NaCl leads to the formation of traditional cubic SAPO-34. N 2 sorption isotherm and NH 3 temperature programmed desorption (NH 3-TPD) analyses indicate that floral SAPO-34 has the largest pore volume but lowest strong acidity compared with other samples with traditional cubic morphology. When applied to methanol to olefin (MTO) reactions, floral SAPO-34 shows the comparable yields of propylene and butylenes to other samples but lowest overall olefin yield, which is attributed to the synergistic effect of the largest pore volume and lowest strong acidity.

Characterization and corrosion properties of Ti‐O/HA composite coatings on Mg‐Zn alloy

Biodegradable magnesium alloys have been widely investigated in the field of biomaterials because they can be gradually dissolved and absorbed by the human body without long‐term existence. However, it was found that bare magnesium implants suffered from rapid corrosion. Surface modification is applied to improve the corrosion resistance and biocompatibility of magnesium implants. In this study, Ti‐O/HA composite coatings including typical flakes and nanofibers were fabricated on the Mg‐Zn alloy. The Ti‐O films were deposited on the magnesium alloy by direct current magnetron sputtering, and subsequently coated with HA flakes and nanofibers by electrochemical deposition, respectively. The obtained coatings were investigated by X‐ray diffraction, Fourier Transform Infrared spectroscopy and scanning electron microscopy. The corrosion resistance was evaluated by potentiodynamic polarization and hydrogen evolution tests in simulated body fluid at 37 °C. The results show that the compact Ti‐O films are composed of particles within the size of 100 nm, the outermost HA coatings are predominantly composed of HA and doped with Na+, Mg2+ ions and functional groups. The stronger diffraction and broader peak in nanofibers than typical flakes around 25.8° are ascribed to the preferential growth in orientation (002). The morphology of HA coatings changed from typical flakes into nanofibers with the addition of NaF, the mechanism to explain the difference is also discussed. The corrosion resistance was improved significantly by the coatings, the corrosion rates in the 10 days were 4.13, 1.77, 0.96 and 0.85 mm/y, respectively. Copyright © 2011 John Wiley & Sons, Ltd.

Nanotubular surface and morphology of Ti-binary and Ti-ternary alloys for biocompatibility

The nanotubular surface of Ti-binary and Ti-ternary alloys for biomaterials has been investigated using various methods of surface characterization. Binary Ti-xNb (x = 10, 20, 30, and 40 wt.%) and ternary Ti-30Ta-xNb (x = 3, 7 and 15 wt.%) alloys were prepared by using the high-purity sponges; Ti, Ta and Zr spheres. The nanotube on the alloy surface was formed in 1.0 M H 3PO 4 with small additions of NaF (0.5 and 0.8 wt.%), using a potentiostat. For cell proliferation, an MC3T3-E1 mouse osteoblast was used. The surface characteristics were investigated using field-emission scanning electron microscope, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. Binary Ti-xZr alloys had a lamellar and a needle-like structure, whereas, ternary Ti-30Ta-xZr alloys had equiaxed grains with a lamellar martensitic α′ structure. The thickness of the needle-like laths of the α-phase increased as the Zr content increased. The nanotubes formed on the α phase and β phase showed a different size and shape appearance with Zr content. As the Zr content increased from 3 to 40 wt.%, the diameter of the nanotubes in Ti-xZr and Ti-30Ta-xZr alloy decreased from 200 nm to 50 nm. The nanotubular Ti-30Ta-15Zr alloy surface with a diameter of 50 nm provided a good osseointegration; cell proliferation, migration and differentiation.

Anomalous effects of concentrated salts on the equimolarly mixed cationic–anionic surfactant mixtures

Effects of alkali metal halides (NaX, X = F−, Cl−, Br−, I−; KX, X = Cl−, Br−, I−; and CsCl) on the morphology of the aggregates of decyltriethylammonium bromide and sodium decylsulfonate (C10NE–C10SO3) mixtures with equimolar ratios were studied by static/dynamic light scattering and viscosity measurements. The average hydrodynamic radii of the aggregates, the apparent aggregation number, and the relative viscosity as functions of both the concentrations of surfactants and added salts were investigated, respectively. It showed that the addition of a small amount of NaX (e.g., 0.1 M) had only small effects on the C10NE–C10SO3 vesicles. However, striking anion specificity, which differed anomalously with the anions of salts varying from F− to I−, was observed when large amounts of NaX (e.g., 1 M) were added. The size of the C10NE–C10SO3 aggregates was normally increased and then a liquid–liquid phase separation occurred with the addition of NaF; meanwhile, the addition of NaCl had little effect on the C10NE–C10SO3 aggregates under experimental conditions; however, the size of the C10NE–C10SO3 aggregates was abnormally decreased when high concentrations of NaBr or NaI (up to 2 M) were added, implying a vesicle-to-micelle transition which might be due to a decrease in the intramicellar attraction between oppositely charged headgroups by electrical shielding, and the mixtures still remained homogeneous. A cation specificity of added salts was also observed with the increase of the ionic radii from Na+ to Cs+. However, it was noted that the influence of increasing the ionic radii of cations on the aggregate size was not as pronounced as that of anions in the presence of high concentrations of salts. The aggregates of C10NE–C10SO3 became a little smaller when concentrated alkali metal halides with bigger cations were added into this homogeneous equimolar cationic–anionic surfactant mixture. Both the observed cation and anion specificities were consistent with the Hofmeister series.

Preparation of ceramic coating on Ti substrate by Plasma electrolytic oxidation in different electrolytes and evaluation of its corrosion resistance

Ceramic oxide coatings (titania) were produced on Ti by micro-arc oxidation in different aluminate and carbonate based electrolytes. This process was conducted under constant pulsed DC voltage condition. The effect of KOH and NaF in aluminate based solution was also studied. The surface morphology, growth and phase composition of coatings were investigated using scanning electron microscope and X-ray diffraction. Corrosion behavior of the coatings was also examined by potentiodynamic polarization and electrochemical impedance spectroscopy. It was found that the sparking initiation voltage (spark voltage) had a significant effect on the form and properties of coatings. Coatings obtained from potassium aluminate based solution had a lower spark voltage, higher surface homogeneity and a better corrosion resistance than the carbonate based solution. Addition of NaF instead of KOH had improper effects on the homogeneity and adhesion of coatings which in turn caused a poor corrosion protection behavior of the oxide layer. AC impedance curves showed two time constants which is an indication of the coatings with an outer porous layer and an inner compact layer.

Phenomena of Nanotube Nucleation and Growth on New Ternary Titanium Alloys

Ti-30Nb-xZr and Ti-30Ta-xNb alloys have been investigated using various methods of surface nanotube formation. Ternary Ti-30Nb-xZr (x = 3 and 15 wt%) and Ti-30Ta-xNb (x = 3 and 15 wt%) alloys were prepared by using high-purity sponge Ti (Grade 4, G&S Titanium, USA), Ta, Zr and Nb spheres. The two groups of ternary Ti alloys were prepared using a vacuum arc melting furnace. Nanotube formation was carried out with a conventional three-electrode configuration with the Ti alloy specimen, a platinum counterelectrode, and a saturated calomel (SCE) reference electrode. Experiments were performed in 1 M H3PO4 with small additions of NaF (0.1-0.8 wt%), using a potentiostat. Nanotubes formed on the surfaces of the two ternary Ti alloys were examined by field emission scanning electron microscopy, EDS and XRD. The Ti-30Ta-xZr alloys had microstructure with entirely needle-like constituents; the thickness of the needle-like alpha-phase increased as the Zr content increased. The Ti-30Nb-xZr alloys had equiaxed microstructures of the beta-phase, and increasing amounts of the needle-like alpha phase appeared at the grain boundaries of the beta-phase as the Zr content increased. The nanotubes were nucleated and grew mainly on the beta phase for the Ti-30Ta-3Zr and Ti-30Nb-3Zr alloys, which had nanotubes with uniform shape, but the nanotubes were nucleated at the alpha phase for the Ti-30Ta-15Zr and Ti-30Nb-15Zr alloys, which had nanotubes with irregular shape and diameters of two sizes. The diameter and depth of the nanotubes could be controlled, depending upon the alloy composition and composition of the surface oxide films (TiO2, Nb2O5, Ta2O5, and ZrO2). It is concluded that this research that selection of the appropriate alloying element can allow significant control of the nanotopography of these Ti alloy surfaces and that it is possible to control the surface nanotube size to promote long-term osseointegration for clinical dental or orthopedic use.

Humus status of different soils affected by pollution with fluorides from aluminum production in the Baikal region

The effect of pollution by fluorides from aluminum production on the humus status in different types of arable soils was studied in field experiments. They included modeling of a high pollution level by addition of NaF prevailing in industrial air emissions. The negative effect of fluorides on the humus status, related to an increase in the mobility of humic substances, was more pronounced in gray forest soil than in sod-meadow soil. This depended on the soil physicochemical properties determining the buffer capacity toward NaF and the content of water-soluble fluorides.

Storage lipids as a source of carbon skeletons for asparagine synthesis in germinating seeds of yellow lupine ( Lupinus luteus L.)

The 14C-acetate metabolism and regulatory functions of sucrose and sodium fluoride (NaF) were examined in embryo axes and cotyledons isolated from yellow lupine seeds and grown in vitro. After 15 min of incubating organs in solutions of labeled acetate, more radioactivity was found in amino acids (particularly in glutamate, asparagine and glutamine) than in sugars. After 120 min of incubation, 14C was still localized mainly in amino acids (particularly in asparagine and glutamate). The 14C atoms from position C-1 of acetate were mostly localized in the liberated 14CO 2, whereas those from position C-2 were incorporated chiefly into amino acids, sugars and the insoluble fraction of the studied organs. The addition of NaF caused a decrease in the amount of 14C incorporated into amino acids and in the insoluble fraction. The influence of NaF on incorporation of 14C into sugars differed between organs. In embryo axes, NaF inhibited this process, but in cotyledons it stimulated 14C incorporation into glucose. The release of 14CO 2 with the C-1 and C-2 carbon atoms from acetate was more intensive in embryo axes and cotyledons grown on a medium without sucrose. This process was markedly limited by NaF, which inhibits glycolysis and gluconeogenesis. Alternative pathways of carbon flow from fatty acids to asparagine are discussed.