La Addition Research Articles

Effect of linoleic acid supplementation on triglyceride content and gene expression in milk fat synthesis in two- and three-dimensional cultured bovine mammary epithelial cells

In this study, the effect of 0, 40, and 80 μmol/L of LA on triglyceride (TG) content was evaluated, as well as the mRNA expression of genes involved in milk fat synthesis in bovine mammary epithelial cells (BMECs) which were cultured in two-dimensional (2D) and three-dimensional (3D) models. TG content was measured with a TG determination kit, and the expression of genes was measured with real-time quantitative polymerase chain reactions (RT-qPCR). Adding 80 μmol/L of LA significantly increased intracellular TG content in both 2D and 3D cultured BMECs (p < .05). The mRNA expression of diacylglycerol acyltransferase 2 (DGAT2) and peroxisome proliferator-activated receptor-γ (PPARG) increased with the addition of 80 and 40 μmol/L of LA, respectively (p < .05), whereas the expression of PPARG was downregulated in the 2D model (p < .05). Adding LA significantly reduced the expression of sterol regulatory element-binding transcription factor 1 (SREBF1), acetyl-CoA carboxylase (ACC), fatty acid synthase (FASN), stearoyl-CoA desaturase (SCD), and fatty acid-binding protein 3 (FABP3) compared to the control group (p < .05). Altogether, TG content in BMECs and expression of genes involved in milk fat synthesis were significantly higher with addition of LA under 3D BMECs culture model than those of 2D (p < .05), and 40 and 80 µmol/L of LA inhibited the de novo synthesis of fatty acids and promoted the expression of DGAT2 and accumulation of TG. The mRNA expression of PPARG in 3D model was increased by addition of 40 μmol/L LA, whereas it was downregulated in 2D model.

Influence of Wire Initial Composition on Anode Microstructure and on Metal Transfer Mode in GMAW: Noteworthy Role of Alkali Elements

Metal Active Gas (MAG) welding in presence of Argon and CO2 mixture as shielding gas is a largely developed process allowing the transfer of the liquid metal from the consumable wire anode to the workpiece according to various modes (short-arc, globular, spray-arc). The CO2 presence in the shielding gas leads to the formation of an oxide layer, or gangue, wrapping the droplet, limiting the access to the spray-mode transfer, taking into account the low conductivity and the high viscosity of this layer. Several electrodes of various compositions have been tested thanks to Flux Cored Arc Welding, to limit the gangue formation or its negative contribution, based on Ti, La, Zr and alkali metals addition or reduction in silicon content. The results are interpreted considering the metal transfer mode for a given current intensity (330 and 410 A), with various CO2 concentrations in the shielding gas. Finally, the role of the gangue, compared to the other factors governing the droplet detachment, is discussed. A decrease in silicon content limits significantly the gangue formation and gives access to spray arc transfer up to 30 vol.% of CO2 at 330 A. Titanium addition leads to the same results. The tests in presence of zirconium proved the conductivity improvement of the gangue. The addition of alkali allows to stabilize the spray arc up to the noteworthy value of 60 vol.% of CO2 at 330 A, supporting the hypothesis of a strong influence of viscosity on droplets detachment in the process.

Synthesis and characterization of a Mg[sbnd]Ni-RE alloy for hydrogen storage

The synthesis and characterization of a MgNi alloy having La and Ce as catalysts, have been performed. The alloy behavior was studied at given fixed temperature and pressure during hydrogen absorption/desorption tests. The La and Ce addition was carried out starting from a commercial alloy, named “Firesteel”. The alloy synthesized has the following formula Mg68Ni26M5X, where X represents Si and Fe impurities and M stands for the mixture of rare earths metals. The alloy has been prepared by a melting process in an induction furnace equipped with a centrifugal casting system and then grinded, by both hydraulic press and ball milling. The alloy has been characterized by SEM, BET, XRD, DSC-TGA analysis and by a mass flow measurement apparatus. The experiments on alloy sample showed that, after activation, hydrogenation occurs at 300 °C in three stages at three different pressures: 3, 4 and 7 atm, involving respectively 0.15 wt%, 0.4 wt% and 2.2 wt% of hydrogen absorbed. Reversible hydride dehydrogenation, inside the mass flow measurement apparatus, requires a working temperature of 350 °C to obtain, with remarkable reaction rate, about 2.7%, hydrogen desorption.

The Influence of La and Ce Addition on Inclusion Modification in Cast Niobium Microalloyed Steels

The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of inclusions (composition, geometry, size and volume fraction), which can potentially lead to the improvement of some mechanical properties such as the toughness in steels. In this study, different amounts of RE were added to a niobium microalloyed steel in as-cast condition to investigate its influence on: (i) type of inclusions and (ii) precipitation of niobium carbides. The characterization of the microstructure by optical, scanning and transmission electron microscopy shows that: (1) the addition of RE elements change the inclusion formation route during solidification; RE &gt; 200 ppm promote formation of complex inclusions with a (La,Ce)(S,O) matrix instead of Al2O3-MnS inclusions; (2) the roundness of inclusions increases with RE, whereas more than 200 ppm addition would increase the area fraction and size of the inclusions; (3) it was found that the presence of MnS in the base and low RE-added steel provide nucleation sites for the precipitation of coarse niobium carbides and/or carbonitrides at the matrix–MnS interface. Thermodynamic calculations show that temperatures of the order of 1200 °C would be necessary to dissolve these coarse Nb-rich carbides so as to reprecipitate them as nanoparticles in the matrix.

Microstructure and mechanical properties of Mg[sbnd]14Li[sbnd]1Al[sbnd]0.3La alloys produced by two-pass extrusion

The microstructure of as-cast and extruded Mg14Li1Al(0, 0.3) La alloys was examined with XRD, OM, SEM, and EDS. The mechanical properties of the extruded specimens with and without La were compared. The results show that La addition has an obvious effect on the microstructure of the as-cast LA141 alloy by reducing the average grain size from 600 to 220 μm. β-Li and LiMgAl2 phases are observed in both alloys, and long-rod-shaped Al2La phase is also observed in the La containing alloy. After extrusion, Al2La phases are short-rod-shaped and distribute evenly in the alloy. LA1410.3La alloy has higher elongation (34%), which is attributed to refined microstructure and weak texture due to short-rod-like Al2La phase.

Effect of La inoculation on composition, content, granularity and mechanical properties of in-situ Al-30 wt%Mg2Si Composite

In this paper, the phase composition and content of Al-30wt%Mg2Si composite prepared by in-situ process have been investigated; and the effect of different addition of La inoculation on microstructure, granularity and mechanical properties of Al-30%Mg2Si composite have been studied. Scanning electron microscope (SEM) and X-ray diffraction (XRD) images show that the phase composition and content of Al-30wt%Mg2Si composite agree with pseudo-binary Al-Mg2Si phase diagram. The effect of La inoculation on microstructure indicates that La addition can change the morphology of primary Mg2Si particles and refine the particle size of primary Mg2Si. When the La addition reaches to 0.8wt%, the refinement effect of Al-30%Mg2Si composite is the best. Similarly, the results reveal that La addition can effectively improve the ultimate tensile stress (UTS), breaking elongation (BE) and Vickers microhardness (VM) values. When La addition is over 0.8wt%, primary Mg2Si particles become coarsening and mechanical properties decline. The crystal size was characterized by XRD and deduced by Cauchy and Gaussian approximation. The relationship between crystal size and UTS or VM can be described by Hall-Petch relation. The linear fitting degree of UTS is better.

Microstructure and Corrosion Properties of Homogenized Mg-4Zn-1La Magnesium Alloy

In this study, microstructure and corrosion behaviour of homogenized Mg-4Zn-1La magnesium alloy was investigated. Mg-4Zn-1La alloy was produced by low-pressure die casting method. Homogenization treatments were performed at 350 °C and 400 °C for 12, 18, 24 and 48 hours, followed by rapid cooling in water at room temperature. Microstructure characterizations showed that La addition led to a formation of semi-continuous network structure and islands of second phases which identified as T-phase (Mg7Zn3RE). A significant amount of second phase dissolution and an increase in a-Mg grain size with increasing both homogenization time and temperature was observed. Homogenization treatment led to an improvement in corrosion resistance of Mg-4Zn-1La alloy. Homogenization at 400 °C resulted in better corrosion resistance than homogenization at 350 °C for all homogenization duration.

Microstructure and Corrosion Properties of Homogenized AZ31 and AZ31+1%La Magnesium Alloys

Energy efficiency and decreasing emission of greenhouse gasses emerge that the importance of Mg alloys. Mg alloys can begin to supersede the steel and aluminum for structural applications, thanks to the developing of mechanical properties or corrosion resistance of Mg alloys. Rare earth metals such as Gd, Ce, Y and Nd have been utilized at AZ31 Mg alloys for this purpose in recent years. In this study, the effects of La addition and homogenization heat treatment on microstructure, hardness properties and corrosion resistance of AZ31 and modified AZ31 Mg alloys produced by low pressure die casting method were investigated.

Effect of lanthanum addition on the fabrication of REBa2Cu3Oy (RE=Gd, Sm and Dy) thin films by metal organic deposition using fluorine-free solutions

The effects of lanthanum (La) additions of 0.5–10 mol% on the superconducting properties and crystal growth of REBa2Cu3Oy (REBCO, RE = Gd, Sm, and Dy) films fabricated by the fluorine-free metal-organic deposition method using 2-ethylhexanate solutions were investigated. La-doped REBCO films showed the decrease in the number density of holes on the film surface and the increase in the XRD peak intensity of the REBCO superconducting phases. La-added GdBCO with La contents of 0.5–3 mol%, and SmBCO and DyBCO films with La contents of 0.5–10 mol% showed improved critical current density (Jc) at the self-magnetic field compared to the pure films. For the GdBCO film, the Jc value at the self-magnetic field increased from 1.32 to 2.38 MA/cm2 upon La addition.

Effects of La Microalloying on Microstructure Evolution of Pure Copper

The absorptivity of La in pure copper and the effects of La microalloying on microstructure evolution of pure copper were studied by adding different La contents to pure copper under vacuum condition. The microstructure of copper ingots with different La contents were synthetically analyzed by means of optical microscope (OM) and scanning electron microscope (SEM), and the content of La in ingots was tested using inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results showws that the absorptivity of La in pure copper was more than 90% under vacuum condition and the burning rate was mainly determinated by autoxidation of La and the reaction with impurity elements in copper. The microstructure of copper ingot was refined with La addition. The columnar to equiaxed transition (CET) occured with 0.14% La addition and the microstructure of copper ingot was full equiaxed grains when La content was 0.16%. The CET mechanism was that the constitutional supercooling in copper melt was increased with La addition. The tensile strength of copper alloys could be improved slightly, while the elongation was decreased a little after La alloying.

Effect of La, Mg and Mo additives on dispersion and thermostability of Ni species on KIT-6 for CO methanation

Ni catalysts supported on mesoporous silica KIT-6 with and without promoters (La, Mg and Mo) were prepared by co-impregnation and their catalytic performances on CO methanation were conducted in fixed-bed reactor. As a result, promoters had a negligible benefit to the dispersion of Ni particles since Ni species were highly dispersed on KIT-6. While the metal Ni surface area was reduced due to partial coverage of metal Ni by promoters. Besides the improvement of the promoters (La and Mo) on CO methanation activity, a suitable Ni- support interaction can hindrance the aggregation of Ni particles on 0.5MoNi/KIT-6 during thermal treatment. While the aggregation of Ni particles was severe on Ni/KIT-6 and 0.3LaNi/KIT-6 due to the weak interaction between Ni and support. Furthermore, Mg enhanced the interaction between Ni and KIT-6 by forming NiO-MgO solid solution, but simultaneously some “unsupported” free and “surface rich” Ni species was formed, which would aggregate into larger particles (ca. 25×40nm) during thermal treatment. It was worth mentioning that high pressure (3MPa) improved the catalytic activities and thermostability of catalysts for CO methanation but the aggregation of metal particles were more severe after thermal treatment in reactants under high temperature.

Influence of rare earth (Ce and La) addition on the performance of Al-3.0 wt%Mg alloy

The influences of rare earth elements (cerium and lanthanum) on the microstructure and phases of Al-3.0 wt%Mg alloys used for electromagnetic shielding wire were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The mechanical properties and electrical resistivity were also investigated. The results indicated that a certain content of rare earth could improve the purification of the aluminum molten, enhance the strength, and reduce the electrical resistivity of Al-3.0 wt%Mg alloys. The strength reached the top value when RE content was 0.3 wt% while the alloy with 0.2 wt% RE addition had the smallest electrical resistivity. The elongation varied little when RE addition was no more than 0.2 wt%. But the excessive addition of rare earth would be harmful to the microstructure and properties of Al-3.0 wt%Mg alloys.

Linoleic acid, α-linolenic acid and enterolactone affect lipid oxidation and expression of lipid metabolism and antioxidant-related genes in hepatic tissue of dairy cows.

Although beneficial effects have been attributed to PUFA supplementation in high-yielding dairy cows, diets rich in PUFA may also increase oxidative stress in tissues such as the liver. To fully exploit the health benefits of PUFA, we believe that the addition of natural antioxidants could help in preventing oxidative damage. Using an in vitro precision-cut liver slices (PCLS) tissue culture system, we investigated the effects of different linoleic acid (LA, n-6):α-linolenic acid (ALA, n-3) ratios (LA:ALA ratio of 4, LA:ALA ratio of 15 and LA:ALA ratio of 25) in the presence or absence of the antioxidant enterolactone (ENL) on (1) the mRNA abundance of genes with key roles in hepatic lipid metabolism, oxidative stress response and inflammatory processes, (2) oxidative damages to lipids and proteins and (3) superoxide dismutase activity in early-lactating dairy cows. The addition of LA and ALA to PCLS culture media increased oxidative damage to lipids as suggested by higher concentrations of thiobarbituric acid reactive substances and increased the expression of nuclear factor erythroid 2-related factor 2 target genes. The addition of ENL was effective in preventing lipid peroxidation caused by LA and ALA. Transcript abundance of sterol regulatory element-binding transcription factor 1 and its lipogenic target genes acetyl-CoA carboxylase α, fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD) was decreased with LA and ALA, whereas ENL decreased FASN and SCD gene expression. Our results show that addition of LA and ALA to PCLS culture media lowers hepatic lipogenic gene expression and increases oxidative damages to lipids. On the other hand, addition of ENL prevents oxidative damages provoked by these PUFA.

Hydrogen Environment Assisted Cracking of a Modern Ultra-High Strength Martensitic Stainless Steel

A modern martensitic stainless steel (Ferrium® PH48S™) resists hydrogen environment assisted cracking (HEAC) in aqueous NaCl at ultra-high yield strengths (1,400 MPa to 1,600 MPa). HEAC is transgranular, because of increased steel purity and La addition, compared to severe intergranular HEAC in Custom® 465-H900 without rare earth elements. Minimum threshold for HEAC (KTH) is low (8 MPa√m to 17 MPa√m) for each steel under substantial cathodic polarization. Transgranular HEAC occurs along martensite packet and {110}α′-block interfaces in PH48S, likely a result of H decohesion enabled by localized plasticity. Martensite transformation produces a large area of coincident site lattice interfaces in the refined microstructure of PH48S. However, a susceptible network of random packet/block interfaces is connected in 3D to limit interface engineering. Nanoscale strengthening precipitates in PH48S reduce effective H diffusivity to the mid-10−10 cm2/s range, because of reversible H trapping with a binding energy of 12 kJ/mol. This diffusivity reduces the Stage II growth rate by 1 to 3 orders of magnitude compared to C465 and carbide strengthened ultra-high strength steels. PH48S and C465 are nearly immune to HEAC when cathodically polarized by 50 mV to 500 mV, attributed to a minimum in occluded-crack tip overpotential for H production. The breadth of this protective-potential window increases with decreasing steel strength. Increased Cr does not degrade HEAC resistance, suggesting that crack passivity dominates cation acidification to reduce H production and/or uptake. A quantitative decohesion model effectively predicts the potential dependence of da/dtII using crack tip H solubility reverse calculated from a KTH model.

The Effect of Lanthanum Addition on the Microstructure and Mechanical Properties of A390 Aluminium Alloy

Aluminium alloys are widely used in the industries and for biomedical applications, because when compared with other materials they provide a high strength-to-weight ratio, better wear resistance, less density, and low coefficient of thermal expansion. However, these alloys possess some limitations in terms of the interactive effects of additives. Therefore, the target of this research is to study the influence of Lanthanum addition of 0.5, 1.0, and 1.5 wt% on the microstructure and mechanical properties of hypereutectic Al–Si alloy. Optical microscopic test, FESEM spectroscopy, XRD, and mechanical properties testing, such as tensile, impact, and hardness test were carried out for characterization purposes. The result indicates the formation of intermetallic compounds, while the value of the secondary dendrite arm spacing became smaller with increasing La addition. The optimum modification of A390 alloy eutectic structure was at 1.0 wt% of La, which improved the ductility from 0.7 to 1.8% and a recorded increase in tensile strength from 100 to 150 MPa.

Improve Activity and Stability of Ni-Ce0.8Sm0.2O1.9 As the Anode of a Methanol Fuelled Solid Oxide Fuel Cell

Solid oxide fuel cells (SOFCs) are electrochemical devices those convert chemical energy in fuels directly into electricity. Compared with H2, commercial hydrocarbon fuels can be safely stored and are more readily available, which could reduce the overall operation cost. Therefore, direct electrochemical oxidation of hydrocarbons into electricity using SOFCs is appealing. However, there are many operational problems those still need to be solved. The typical NiO-YSZ anode material has excellent catalytic properties for fuel oxidation and good electrical conductivity, while it experiences serious carbon deposition with hydrocarbons as fuels. Therefore, there is a need for developing new kinds of carbon resistant SOFC anode materials for the utilization of hydrocarbon fuels. In this work, Mo is utilized to modify the Ni-Ce0.8Sm0.2O1.9 (SDC) anode. The NiO-MoO3-SDC anode materials are prepared by impregnation technique, which are reduced to SDC and Ni-Mo alloy phases in H2 atmosphere. SOFCs with Ni-Mo-SDC composite anodes are fabricated and tested with methanol as fuel. The addition of Mo into Ni–SDC anode effectively improves performance and stability of the single cell at 700 oC. The anode with a mole ratio of Mo to Ni of 0.03:1 (Ni-3Mo-SDC) exhibits the lowest polarization resistance. The cell with that anode and SDC-carbonate composite electrolyte exhibits a maximum power density of 680 mW cm-2 at 700 oC. The stability of the cell is enhanced with the increase of the content of Mo in the anode. In order to further improve the cell performance and stability, rare earth elements (La, Pr and Sm) are introduced into Ni-3Mo-SDC. The effects of La, Pr and Sm addition on the catalytic activity for methanol pyrolysis and coking resistance of the Ni-3Mo-SDC anode are examined. The electrochemical performance of the SOFC is enhanced with introducing La and Sm into the anode. The cell with La addition in the anode shows a maximum power density of 765 mW cm-2 at 700 oC with methanol as fuel. The addition of La, Pr and Sm into Ni-3Mo-SDC anode improves the stability of the cell, which is mainly attributed to the decreased amount of carbon deposition with a high graphitization degree.

Effect of lanthanum promoter on the catalytic performance of levulinic acid hydrogenation over Ru/carbon fiber catalyst

A series of La-modified Ru/carbon fiber (CF) catalysts was designed, and used for the conversion of levulinic acid (LA) into γ-valerolactone (GVL) under batch reactor conditions. The dopant of Lanthanum improved the hydrogenation activity from 37.7μmolgcat−1s−1 to 216.1μmolgcat−1s−1 when the mole La/Ru was 0.5 on the catalyst. Even in low temperatures, the Ru1La0.5/CF catalyst also showed a high activity in the hydrogenation of LA. Aiming at a detailed understanding the role of Ru-La interactions in the catalyst, the Ru1Lax/CF catalysts was characterized by the H2-TPR, H2-TPD, CO2-TPD, XPS, TEM and CO chemsorption. The electron density of Ru species has been enhanced by La addition to Ru/CF. The hydrogenation activity was a consequence of the amount of Ru active site and the promoting effect of Ru-La interaction.

Quantitative Analysis of La and Al Additives Role on Dipole Magnitude Inducing Vt Shift in High-K/Metal Gate Stack

Voltage drop induced by an electrical dipole layer after the incorporation of La or Al in high- $k$ /metal gate-stack has been measured on nominal and beveled-SiOx devices and linearly correlated to the effective La/Al dose into the high- $k$ /SiOx stack determined through X-ray fluorescence spectroscopy. Electrical dipoles were experimentally estimated to be around −55 and +40 meV for each $1\times 10^{14}$ at/cm2 of effective La and Al dose, respectively.

Structural, magnetic and photocatalytic characterization of Bi1−x La x FeO3 nanoparticles synthesized by thermal decomposition method

Single-phase La-substituted bismuth ferrite (Bi\(_{\boldsymbol {1-x}}\)La\(_{\boldsymbol {x}}\)FeO\(_{\mathbf {3}}\)) nanoparticles have been synthesized by thermal decomposition of a glyoxylate precursor. The crystal structure transition of BiFeO\(_{\mathbf {3}}\) from the rhombohedral (R3c) to the cubic \(\boldsymbol {Pm}\bar {\mathbf {3}}\boldsymbol {m}\) structure by La addition was confirmed by X-ray diffraction and infrared spectrometry methods. Furthermore, the Bi\(_{\boldsymbol {1-x}}\)La\(_{\boldsymbol {x}}\)FeO\(_{\mathbf {3}}\) nanoparticles showed a weak ferrimagnetism behaviour, while the magnetization increased from 0.18 to 0.48 emu g\(^{\mathbf {-1}}\) with La substitution. The Bi\(_{\boldsymbol {1-x}}\)La\(_{\boldsymbol {x}}\)FeO\(_{\mathbf {3}}\) nanoparticles exhibited strong absorption in the visible region with the optical band gap calculated from Tauc’s plot in the range of 2.19–2.15 eV. Furthermore, the effects of La substitution on the photodegradation of the methylene blue (MB) under visible light were also studied. The photodegradation of MB dye was enhanced from 64 to \(\sim \)99% with increasing La substitution from \(\boldsymbol {x =}\) 0 to 0.1 and then decreased to 8% for \(\boldsymbol {x =}\) 0.15.

Effect of La addition on the microstructure and martensitic transformation of Ni-Ti-La alloys

The effect of the addition of the rare earth element La on the microstructure and martensitic transformation behavior of Ni50Ti50-xLax (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) alloys was investigated experimentally. The microstructure of Ni-Ti-La alloys consists of the near-equiatomic TiNi matrix and LaNi precipitates. One-step martensitic transformation was observed in all Ni-Ti-La alloys. The martensitic transformation start temperatures decrease gradually with the increase of La fraction in Ni-Ti-La alloys.