Nanogravimetry study of the initial stages of anodic surface oxide film growth at Au in aqueous HClO4 and H2SO4 by means of EQCN

The dependence of the initial stages of anodic oxide film growth at Au on time or log time, τ_h, was investigated by means of nanogravimetry using a electrochemical quartz crystal nanobalance (EQCN) which provides a new dimension for such studies, complementary to voltammetry, chronoamperometry and ellipsometry. Films were formed potentiostatically in sulphuric or perchloric acids. The mass to charge ratio determined over the potential range corresponding to Au oxide formation is found to be ca. 6-7 g per mole of electrons, which is close to the value expected for formation of Au/O_ads on the electrode surface. The relations between charge and log τ_h, or mass and log τ_h, were evaluated. The charge for prior formation of O species, determined from reduction voltammetry, increases linearly with the log of the holding time. However, it is of special interest that the mass change in HClO₄ solutions does not increase linearly with the log of the holding time. This is interpreted in terms of co-adsorption of anions and displacement of water molecules. The results enable mechanisms of oxide film formation at Au to be critically appraised.     

Anodic oxidation of Co(II) complexes with amines on a rotating Au electrode: Ligand effects in relation to the application for autocatalytic metal deposition

For the comparison of the electrochemical activity of Co(II)-amine complexes, the electrochemical response of an Au rotating disk electrode in alkaline Co(II)-glycine solutions to six amines: ethylenediamine (en), propane-1,2-diamine (pn-1,2), propane-1,3-diamine (pn-1,3), cyclohexane-1,2-diamine (chn), butane-1,4-diamine (bn), diethylenetriamine (dien), was studied. Addition of amines tested (except for bn) in mM levels shifts the open-circuit potential to more negative values by up to 0.5 V and enhances dramatically the anodic Co(II) oxidation current, as a result of Co(II) complex transformation into more stable and electrochemically active Co(II)-amine species. The effect of amines on the open-circuit potential changes in the line: dien ∼ en > pn-1,2 ∼ chn > pn-1,3 ? bn, and on the anodic current in the sequence: dien ∼ en > pn-1,2 > chn > pn-1,3 ? bn. The procedure described helps to select ligands for Co(II) complexes used as reducing agents in electroless plating solutions. The amines of high electrochemical response: dien, en, pn-1,2, and possibly, chn, are suitable for electroless copper deposition, pn-1,3 (a lower response), for electroless silver deposition, and bn (no response), not suitable for electroless plating solutions.     

草酸在表面合金电催化剂上还原过程的循环伏安和原位红外反射光谱研究

采用自行研制的碳载表面合金电催化材料 (Surfacealloy/GC)作为研究电极 ,通过电化学方法和电化学原位FTIR反射光谱等技术 ,对该催化剂在电有机合成中的性能进行研究。结果表明 :所研制的Surfacealloy/GC对草酸的加氢还原表现出很高的电催化活性 ,草酸的还原电位为 - 0 .40V ,与通常用的阴极铅材料相比 ,正移约6 0 0mV ;电化学原位FTIR反射光谱研究结果指出 ,草酸的还原产物主要为乙醛酸 ,表明该电极在较低的过电位下就能还原草酸生成乙醛酸。     

Dissolution of Soap Scum by Surfactant. Part II: Effects of NaCl and Added Chelant on Equilibrium Solubility and Dissolution Rate of Calcium Soap Scum in Amphoteric Surfactant Solutions

The effects of solution pH and NaCl on the equilibrium solubility and dissolution rate of a model soap scum (calcium octadecanoate or calcium stearate) in aqueous solutions of dimethyldodecylamine oxide surfactant (DDAO) with and without chelant disodium ethylenediaminetetraacetate are reported. The equilibrium solubility and dissolution rate of soap scum increased with increasing solution pH when the chelant was added in the DDAO system while in the chelant-free systems the opposite trend was observed. The added NaCl has an ambiguous effect on the solubility and dissolution rate of soap scum in the absence of chelant, but a small level of added NaCl reduces both solubility and the dissolution rate constant in the presence of chelant. Both equilibrium and kinetics of dissolution are maximized at high pH with DDAO/chelant and no added salt.     

Adsorption behavior of terephthalic acid on Au(1 0 0), Au(1 1 1) and Au(1 1 0) electrodes in neutral solution

Adsorption of terephthalic acid on Au(1 0 0), Au(1 1 1) and Au(1 1 0) electrodes in neutral solution has been investigated using in situ Fourier transform infrared (FT-IR) spectroscopy, differential capacity measurements and scanning tunneling microscopy (STM). At negative potentials, the terephthalate anions in solution adsorb in a flat orientation onto the electrode via the π electrons of the aromatic ring. At positive potentials, the terephthalate anions adsorb in a vertical orientation via the oxygen atoms of one of the carboxyl groups as a form of dianion. At more positive potentials, the anions adsorb in a vertical orientation as a form of hydrogen terephthalate. For the three electrodes examined, the overtone and/or combination bands, due to vertically oriented hydrogen terephthalate, were observed at 2642 and 2517 cm⁻¹, respectively. For the Au(1 1 1) electrode, STM observations indicated a flat orientation in the form of terephthalic acid.     

Oxidation of formaldehyde and ethanol on Au(1 1 1) and Au(1 1 1) modified by spontaneously deposited Ru in sulfuric acid solution

The oxidation of formaldehyde and ethanol on both pure Au(1 1 1) and Au(1 1 1) modified by approximately 0.3 monolayer (ML) of spontaneously deposited Ru was studied by cyclic voltammetry (CV) in 0.5 M H₂SO₄ solution containing either 0.25 M formaldehyde or 0.35 M ethanol. In situ scanning tunneling microscopy (STM) and CV were employed to characterize the Au(1 1 1) and Ru/Au(1 1 1) surfaces. The oxidation of HCHO on Ru/Au(1 1 1) commences at 0.1 V more negative potential than on pure Au(1 1 1). From 0.25 to 0.55 V vs. (Ag/AgCl), the reaction occurs with increasing current, showing a peak at a potential of 0.43 V. It is assumed that the increasing anodic activity of the Ru/Au(1 1 1) surface is associated with the oxidation of some reaction intermediates, facilitated by the presence of Ru in its metallic state. On the other hand, the oxidation of ethanol on Ru/Au(1 1 1) commences at 0.1 V more positive potential than on pure Au(1 1 1), and proceeds in the potential region from 0.2 to 0.5 V with significantly smaller currents, showing a peak at 0.43 V. This inhibiting effect is explained by the deactivation of the most active Au(1 1 1) step sites by high coverage with Ru islands. The appearance of a small peak at 0.43 V is most likely associated to the oxidation of some intermediates during ethanol oxidation at the Ru/Au step sites formed on the Au(1 1 1) terraces by the presence of a small coverage with Ru islands.     

［BMIM］BF4中马来酸在Pt上的电化学还原和原位红外光谱

采用循环伏安法(CV)、计时电量法(CA) 和电化学原位红外反射光谱 (in situ FTIRS),从分子水平上研究了离子液体［BMIM］BF4中马来酸在Pt电极上的电化学还原过程。结果表明,［BMIM］BF4中马来酸在Pt电极上的还原是受扩散控制的准可逆过程,测得扩散系数为1.0×10^-7cm²·s^-1;in situ FTIRS研究发现,［BMIM］BF₄中马来酸在Pt电极上的还原发生在其中的一个羧基位上,即马来酸首先获得一个电子生成阴离子自由基,随后再获得一个电子生成二价阴离子。     

Adsorption of 2-X-benzoic acids (X = fluoro, chloro, and bromo) on Au(1 0 0) electrode in acidic media studied by IRAS

Adsorption behaviors of 2-fluoro-, 2-chloro-, and 2-bromobenzoic acids on Au(1 0 0) electrode in 0.1 M HClO₄ have been investigated by using in situ reflection adsorption IR spectroscopy and differential capacity measurements. It is found for the 2-substitued benzoic acids that the flat lying adsorbed species is present at negative potentials, and the vertically adsorbed benzoate with both oxygen atoms oriented toward the metal surface is present at positive potentials. A new adsorbed state due to the vertical orientation was observed around 0.75 V only in 2-fluorobenzoic acid solution, as well as the case of benzoic acid. This indicates that the new band is due to the formation of an ordered adsorption layer of the vertical 2-fluorobenzoate, and the formation of the arrangement adsorption is dependent on the size of the adsorbed molecule.     

Activation of VOHPO4 · 0.5H2O in Propane/Air Mixture: Effect on Structural, Morphological, Oxidant’s Behaviour and Catalytic Property of (VO)2P2O7 Catalysts for Propane Oxidation

VOHPO₄ · 0.5H₂O synthesized by VOPO₄ · 2H₂O and isobutanol was activated in a flow of propane/air mixture (1% propane in air) at 673 K for 36, 75 and 132 h. Three vanadyl pyrophosphate catalysts obtained were denoted as VPD36P, VPD75P and VPD132P. The crystallinity of all propane/air pretreated catalysts as shown in XRD increased with the duration of calcination. SEM micrographs showed the formation of more isolated platelets and more prominent rosebud-shape agglomerate as the pre-treatment was longer. Four reduction peaks maxima at 752, 920, 1026 and 1140 were observed in the rate of hydrogen consumption for VPD36P. As the calcination duration increased to 75 h, the H₂ reduction peaks were shifted to lower temperatures at 750, 882, 1004 and 1140 K. When the calcination duration was further increased to 132 h, only three reduction peaks were observed at 752, 952 and 1142 K. Despite the progressively shifted of the major reduction peak maximum as the duration of calcination increased from 36 to 132 h, the lattice oxygen from VPD36P was found to be the most reactive. The catalytic performance for propane oxidation to acrylic acid (AA) showed that VPD36P gave the highest activity (9.6%) with 83.0% of selectivity to AA.     

Effects of mineral addition on the growth morphology of and arachidonic acid production by Mortierella alpina 1S-4

The culture conditions for arachidonic acid (AA) production by Mortierella alpina 1S-4 were investigated by means of a morphological study with the aims of obtaining a high AA yield and scale-up. In a 50-L jar fermentor study, a medium containing 3.1% soy flour and 1.8% glucose with 0.3% KH₂PO₄, 0.1% Na₂SO₄, 0.05% CaCl₂·2H₂O and 0.05% MgCl₂·6H₂O was found to be optimum. The AA yield reached 9.8 g/L/7 d, and the major morphology was small pellets (1–2 mm). However, in the case of the only addition of KH₂PO₄, the major morphology was filaments. The apparent viscosity increased to 2240 cp, thereby requiring a high agitation speed to maintain adequate oxygen tension, which caused mycelial damage due to shear stress and therefore a decrease in the AA yield. When a medium with Na₂SO₄, CaCl₂, and MgCl₂ was used, the major morphology was large pellets (2–3 mm), and mass transfer limitation through the pellet wall caused a decrease in the AA yield. Based on these results, a scale-up study was carried out under the optimal conditions described above. An AA yield of 10.9 g/L/8 d was obtained in a 10-kL industrial fermentor, and the major morphology was small pellets.     

Effects of a new 4-acryloxyethyltrimellitic acid in a visible light-cured dental adhesive on adhesion and polymerization reactivity

A new adhesive-promoting monomer, 4-acryloxyethyltrimellitic acid (4-AET), was synthesized. The effects on the adhesion to bovine dentin and the polymerization reactivity [the inclusion varying from 0 to 10 wt % 4-AET of the experimental light-cured dental bonding resins (adhesive), wherein the adhesives were aged artificially at 50°C over 2 weeks] were investigated, using tensile and shear bond testing, a differential scanning calorimeter (DSC), and a scanning electron microscope (SEM). Tensile and shear bond strengths to ground dentin were not significantly decreased in 4-AET content over 2 weeks of aging, and the optimum concentration of 4-AET was found to be 5 wt %. The correlation between the tensile and shear bond strengths to the dentin was highly positive (r = 0.8517–0.9329) during the 2 weeks. The maximum temperature (T_max) of the polymerization in DSC was affected by the 4-AET content in the positive correlation. The correlation between the T_max and the bond strength to dentin was highly positive (r = 0.8995–0.9644). The SEM study showed that the bonding resin appeared to adhere strongly to ground dentin without the formation of resin-tags in the dentinal tubules. It was suggested that the bonding strength was attributable to the degree of penetration of the 4-AET/HEMA primer into the dentin and the polymerization reactivity of the bonding resin comprising 4-AET. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1057–1069, 1998     

A Kinetic and Mechanistic Study on the Oxidation of Hydroxy Acids by <Emphasis Type="Italic">N</Emphasis>-Bromophthalimide in the Presence of a Micellar System

The kinetics of oxidation of some α-hydroxy acids viz. Tartaric acid (TA) and Malic acid (MA) by N-bromophthalimide (NBP) were studied in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), in perchloric acid medium at 313 K. The oxidation of TA and MA by N-bromophthalimide in the presence of CTAB is faster than in the absence of surfactant. The rate of oxidation of hydroxy acids was found to be in the order: TA > MA. First order kinetics with respect to NBP was observed in the oxidation of both hydroxy acids. The kinetics results indicate that the first order kinetics in hydroxy acids at lower concentrations tends towards a zero order at its higher concentrations. Inverse fractional order in [H⁺] and [phthalimide] were noted throughout its tenfold variation. With a progressive increase in [CTAB], the rate of reaction increased, reaches a maximum value and then constancy in k _Ψ was observed. Variation of [Hg(OAc)₂] and ionic strength (μ) of the medium did not bring about any significant change in the rate of reaction. The applicability of different kinetic models viz. the Piszkiewicz cooperative model, the Raghvan and Srinivasan model, and the Menger–Portnoy model were tested to explain the observed micellar effects. The effect of [CTAB] on the activation parameters was explored to rationalize the micellar effect. The values of rate constants observed at four different temperatures were utilized to calculate the activation parameters. A suitable mechanism consistent with the experimental findings has been proposed. The index of cooperativity and the micelle binding constant have been calculated.

CMAS and ST3GAL4 Play an Important Role in the Adsorption of Influenza Virus by Affecting the Synthesis of Sialic Acid Receptors

Influenza A viruses (IAVs) initiate infection by attaching Hemagglutinin (HA) on the viral envelope to sialic acid (SA) receptors on the cell surface. Importantly, HA of human IAVs has a higher affinity for α-2,6-linked SA receptors, and avian strains prefer α-2,3-linked SA receptors, whereas swine strains have a strong affinity for both SA receptors. Host gene CMAS and ST3GAL4 were found to be essential for IAV attachment and entry. Loss of CMAS and ST3GAL4 hindered the synthesis of sialic acid receptors, which in turn prevented the adsorption of IAV. Further, the knockout of CMAS had an effect on the adsorption of swine, avian and human IAVs. However, ST3GAL4 knockout prevented the adsorption of swine and avian IAV and the impact on avian IAV was more distinct, whereas it had no effect on the adsorption of human IAV. Collectively, our findings demonstrate that knocking out CMAS and ST3GAL4 negatively regulated IAV replication by inhibiting the synthesis of SA receptors, which also provides new insights into the production of gene-edited animals in the future.     

Effects of ferulic acid,an allelopathic compound,on net P,K, and water uptake by cucumber seedlings in a split-root system

Since distribution of allelopathic compounds in soils is highly variable, injurious effects by such compounds should be related to the frequency of contact with roots. Experiments were conducted to determine how P, K, and water uptake of cucumber seedlings were affected as the fraction of roots in contact with ferulic acid (FA) was increased. Seedlings were grown in Hoagland's nutrient solution for 14 days and then transferred to 0.5 mM CaSO₄ solution for 24 hr before being placed into a split-root culture system. The containers in the system were filled with 0.5 mM concentrations of KH₂PO₄ and CaSO₄ or 0.5 mM concentrations of KH₂PO₄, CaSO₄, and ferulic acid (FA). Net uptake of P by seedlings (milligrams per seedling) decreased in a curvilinear (concave) manner as the fraction of the roots in contact with FA increased. Net uptake of K (milligrams per seedling) and water (milliliters per seedling) by seedlings decreased linearly as the fraction of the roots in contact with FA increased. Net uptake of P, K, and water by seedlings was reduced 57, 75, and 29%, respectively, when the whole root system was exposed to FA. Net P and K uptake of roots (milligrams per gram root fresh weight) not in contact with FA decreased in a linear and curvilinear (convex) manner, respectively, as the fraction of roots in contact with FA increased. Net P and K uptake of roots in contact with ferulic acid increased in a linear and curvilinear (convex) manner, respectively. Net water uptake of roots (milliliters per gram root fresh weight) not in contact with FA increased in a curvilinear (concave) manner as the frequency of the roots in contact with FA increased. Net water uptake of roots in contact with FA did not show a trend. Transpiration (milliliters per square centimeter) was reduced in a linear manner as the fraction of roots in contact with FA increased. A very slight compensation by roots not in contact with FA for roots in contact with FA was observed for net water uptake rates. No compensation for P and K uptake rates was observed.Paper Mo. 12421 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7643. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned.     

Determination of Cr ions in biological and environmental samples by a chromium(III) membrane sensor based on 5-amino-1-phenyl-1H-pyrazole-4-carboxamide

A highly Cr³⁺-selective ionophore, based on 5-amino-1-phenyl-1H-pyrazole-4-carboxamide (APC) as a carrier, was synthesized in order to obtain a Cr³⁺ ion-selective electrode. The demonstrated characteristics of the sensor included a linear dynamic range between 1.0 × 10^− 6 and 1.0 × 10^− 1 M with a near Nernstian slope of 19.6 ± 0.4 mV per decade, a detection limit of 5.3 × 10^− 7 M, a very good selectivity for Cr³⁺ over other cations in a wide pH range (3.2-6.3). Furthermore, the newly-designed electrode presented a fast response time of 10 s with a lifetime of at least 2 months indicating no considerable potential divergence. The sensor accuracy was investigated by the potentiometric titration of a Cr(III) solution with EDTA as well as the monitoring of Cr(III) in mixtures of three and five different ions. As a result, the developed sensor provided satisfactory results after its application in the Cr³⁺ determination in biological samples (urine and synthetic plasma) and also in wastewater of chromium electroplating industries.     

Effects of supplementation of succinic acid on the production and molecular weight distribution of exopolysaccharides by Antrodia camphorata in batch cultures

The effects of organic acid supplementation on both yields and molecular weight distributions of exopolysaccharide (EPS) of Antrodia camphorata were investigated in shaker flasks and air‐lift bioreactors. In the shaker flask study, five out of six organic acid‐supplemented cultures showed negative effects on cell growth, the exception being pyruvic acid‐supplemented culture; lower number average molecular weights (Mn) of EPS were obtained in all the supplemented cultures. EPS production was enhanced by 31% due to the addition of succinic acid. Optimum product yield was obtained between 2.0 and 3.0 g dm^?3 succinic acid; however, the specific production of EPS increased monotonically as succinic acid concentration was increased from 0 to 5 g dm^?3. Enhancement of EPS yield by 28% and a higher Mn of EPS (around 310 kDa) due to the addition of succinic acid were also demonstrated in an air‐lift bioreactor. In addition, a novel fermentation process resistant to EPS degradation is proposed, based on the inhibition of β‐glucanase activity by the supplementation with succinic acid. Copyright © 2004 Society of Chemical Industry     

Carnosic Acid Attenuates an Early Increase in ROS Levels during Adipocyte Differentiation by Suppressing Translation of Nox4 and Inducing Translation of Antioxidant Enzymes

The objective of this study was to investigate molecular mechanisms underlying the ability of carnosic acid to attenuate an early increase in reactive oxygen species (ROS) levels during MDI-induced adipocyte differentiation. The levels of superoxide anion and ROS were determined using dihydroethidium (DHE) and 2′-7′-dichlorofluorescin diacetate (DCFH-DA), respectively. Both superoxide anion and ROS levels peaked on the second day of differentiation. They were suppressed by carnosic acid. Carnosic acid attenuates the translation of NADPH (nicotinamide adenine dinucleotide phosphate) oxidase 4 (Nox4), p47^phox, and p22^phox, and the phosphorylation of nuclear factor-kappa B (NF-κB) and NF-κB inhibitor (IkBa). The translocation of NF-κB into the nucleus was also decreased by carnosic acid. In addition, carnosic acid increased the translation of heme oxygenase-1 (HO-1), γ–glutamylcysteine synthetase (γ-GCSc), and glutathione S-transferase (GST) and both the translation and nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2). Taken together, these results indicate that carnosic acid could down-regulate ROS level in an early stage of MPI-induced adipocyte differentiation by attenuating ROS generation through suppression of NF-κB-mediated translation of Nox4 enzyme and increasing ROS neutralization through induction of Nrf2-mediated translation of phase II antioxidant enzymes such as HO-1, γ-GCS, and GST, leading to its anti-adipogenetic effect.     

Anti-Growth,Anti-Angiogenic,and Pro-Apoptotic Effects by CX-4945, an Inhibitor of Casein Kinase 2, on HuCCT-1 Human Cholangiocarcinoma Cells via Control of Caspase-9/3, DR-4, STAT-3/STAT-5, Mcl-1, eIF-2α, and HIF-1α

Overexpression of casein kinase 2 (CK2) has an oncogenic and pro-survival role in many cancers. CX-4945 (Silmitasertib) is a CK2 inhibitor with anti-cancerous and anti-angiogenic effects. Up to date, the anti-cancer effect and mechanism of CX-4945 on human cholangiocarcinoma (CCA) remain unclear. This study investigated whether CX-4945 inhibits growth and induces apoptosis of HuCCT-1 cells, a human CCA cell line. Of note, treatment with CX-4945 at 20 μM markedly reduced survival and induced apoptosis of HuCCT-1 cells, as evidenced by nuclear DNA fragmentation, PARP cleavage, activation of caspase-9/3, and up-regulation of DR-4. Although CX-4945 did not affect the phosphorylation and expression of CK2, it vastly inhibited the phosphorylation of CK2 substrates, supporting the drug’s efficacy in inhibiting CK2 and its downstream pathway. Importantly, knockdown of CK2 that partially suppressed the phosphorylation of CK2 substrates resulted in a significant reduction of HuCCT-1 cell survival. In addition, CX-4945 reduced the phosphorylation and expression of STAT-3 and STAT-5 in HuCCT-1 cells, and pharmacological inhibition or respective knockdown of these proteins resulted in significant growth suppression of HuCCT-1 cells. CX-4945 also had abilities to decrease Mcl-1 expression while increasing eIF-2α phosphorylation in HuCCT-1 cells. Furthermore, there was a time-differential negative regulation of HIF-1α expression by CX-4945 in HuCCT-1 cells, and knockdown of HIF-1α caused a significant reduction of the cell survival. In summary, these results demonstrated that CX-4945 has anti-growth, anti-angiogenic, and pro-apoptotic effects on HuCCT-1 cells, which are mediated through control of CK2, caspase-9/3, DR-4, STAT-3/5, Mcl-1, eIF-2α, and HIF-1α.