The Crystal and Molecular Structure of Dianhydrogossypol

Dianhydrogossypol (4,4′-dihydroxy-5,5′-diisopropyl-7,7′-dimethyl-bis(3H-naphtho[1,8-bc]furan-3-one)) was made by refluxing gossypol in m-xylene. Proton NMR spectroscopy was used to confirm that complete conversion was achieved over a time period of several hours. Single crystals of the compound were obtained by slow evaporation from dichloromethane. Diffraction studies indicate that this crystal form is tetragonal with a I4₁/a space group and with cell dimensions of a = b = 33.8265(4) Å, c = 9.1497(2) Å, V = 10469.4(3) Å³ at 100 K. The structure was solved by direct methods and was refined to an R1 value of 0.0415 on 6,408 independent reflections. Dianhydrogossypol exists as a pair of enantiomers within this structure. The two fused planar ring systems are oriented at a 117° angle to each other (i.e., close to perpendicular), and the isopropyl groups are oriented with the ternary carbon hydrogen atoms pointed inward toward the center of the molecule. Repeating groups of four molecules (of the same chirality) pack to form a helical structure that is supported by intermolecular hydrogen bonds. Each helix is surrounded by four neighboring helices that are composed of molecules of the opposite chirality. The helices form the walls of empty channels that are 5–6 Å wide. As has been found for some gossypol crystal forms, the open-channel structure of dianhydrogossypol might be useful for scavenging or carrying small molecules. Additional NMR studies confirm that dianhydrogossypol can be converted directly to gossypol lactol ethers in the presence of anhydrous alcohols.     

Crystallinity of large single crystals of FAU-type zeolites with a wide range of Si/Al ratios

Large colorless single crystals of FAU-type zeolites were synthesized from gels with the composition xSiO₂ : 2.0NaAlO₂ : 7.5NaOH : 454H₂O : 5.0TEA, where x = 2.0–6.0. FAU-type zeolite with Si/Al = 1.26(4) was nearly pure and the maximum size of the single crystals was ca. 150 μm. In case of FAU-type zeolites with Si/Al = 1.54(5), the maximum size of single crystals was ca. 200 μm and the ratio of FAU/impurity was 0.07. The framework Si/Al ratio of the as-synthesized FAU-type zeolite tended to increase with the Si/Al ratio of gel composition. All of the large single crystals had good crystallinities for single-crystal X-ray diffraction, leading to enough numbers of significant reflections which have strong intensity. The structure of a single crystal of dehydrated zeolite Na-X (Si/Al = 1.41(4)) with composition |Na₈₀|[Si₁₁₂Al₈₀O₃₈₄]-FAU per unit cell was determined by X-ray diffraction methods in the cubic space group \( Fd \bar{3} m; \) a = 24.9434(6) Å at 294 K. The structure was refined by using all intensities to the final error indices (using only the 771 reflections for which F _o > 4σ(F _o)), R ₁ = 0.048 (based on F) and R ₂ = 0.188 (based on F ²). In the crystallographic studies, the Si/Al ratio of the synthetic FAU-type zeolite is 1.41(4) which is quite consistent with the SEM–EDS analysis.     

Synthesis and structural refinement of fully dehydrated fully Zn<Superscript>2+</Superscript>-exchanged zeolite Y (FAU), |Zn<Subscript>35.5</Subscript>|[Si<Subscript>121</Subscript>Al<Subscript>71</Subscript>O<Subscript>384</Subscript>]-FAU

The single-crystal structure of |Zn_35.5|[Si₁₂₁Al₇₁O₃₈₄]-FAU per unit cell, a = 24.794(1), dehydrated at 673 K and 1 × 10^?6 Torr, has been determined by single-crystal X-ray diffraction techniques in the space group \( Fd\bar{3}m \) at 294(1) K. The structure was refined using all intensities to the final error indices (using the 930 reflections for which F _o > 4σ(F _o)) R ₁ = 0.0448 (based on F) and wR ₂ = 0.1545 (based on F ²). About 35.5 Zn²⁺ ions per unit cell are found at an unusually large number of crystallographic distinct positions, six. The 0.5 Zn²⁺ ion per unit cell is located at the center of double 6-ring (D6R, site I; Zn(I)-O(3) = 2.642(3) Å and O(3)-Zn(I)-O(3) = 81.23(12) and 98.77(12)°). Two different site-I′ positions (in the sodalite cavities opposite D6Rs) are occupied by 14 and 3 Zn²⁺ ions per unit cell, respectively; these Zn²⁺ ions are recessed 0.67 Å and 1.02 Å, respectively, into the sodalite cavities from their 3-oxygens plane (Zn(I′a)-O(3) = 2.094(3) Å, Zn(I′b)-O(3) = 2.23(5) Å, O(3)-Zn(I′a)-O(3) = 110.32(12)°, and O(3)-Zn(I′b)-O(3) = 100.9(30)°). Site-II′ positions (in the sodalite cavities opposite S6Rs) are occupied by 6 Zn²⁺ ions, each of which extends 0.63 Å into the sodalite cavities from their 3-oxygens plane (Zn(II′)-O(2) = 2.164(3) Å and O(2)-Zn(II′)-O(2) = 112.00(12)°). Twelve Zn²⁺ ions are found at two nonequivalent sites II (in the supercage) with occupancies of 7 and 5 ions, respectively; these Zn²⁺ ions are recessed 0.52 Å and 0.96 Å, respectively, into the supercage from their 3-oxygens plane (Zn(IIa)-O(2) = 2.138(12) Å, Zn(IIb)-O(2) = 2.28(4) Å, O(2)-Zn(IIa)-O(2) = 114.2(10)°, and O(2)-Zn(IIb)-O(2) = 103.7(25)°).     

Preparation,Infra-red,MAS-NMR and Structural Characterization of a New Copper Based Inorganic–Organic Hybrid Compound: [C<Subscript>5</Subscript>H<Subscript>6</Subscript>N<Subscript>2</Subscript>Cl]<Subscript>2</Subscript>CuCl<Subscript>4</Subscript>

The ionic salt [2(C₅H₆N₂Cl)⁺], [CuCl₄]^2? complex of copper(II) has been synthesized and characterized. The X-ray diffraction analysis with a single crystal of this compound showed that the title compound (4-amino-2-chloropyridinium)₂CuCl₄ [(CAP)₂CuCl₄], crystallized at room temperature in the monoclinic system, space group C_2/c (N°.15) and the following : a = 16.0064 (2) Å; b = 7.7964 (10) Å; c = 14.7240 (2) Å; β = 102.497 (10)°; V = 1793.91 (4) ų and Z = 4. The structure was solved by using 1,589 independent reflections down to R value of 0.021. The unit cell is made up of tetrachlorocuprate(II) anions and 4-amino-2-chloropyridinium cations linked together by an extensive hydrogen bond network of types N–H···Cl (N: pyridinium) and N–H···Cl (N: amine), and cation-lone pair of nitrogen element interactions. Solid state NMR spectra showed one and five isotropic resonances, ⁶³Cu and ¹³C, respectively, confirming the solid state structure determined by X-ray diffraction. Impedance spectroscopy study, reported for single crystal, revealed that the conduction in the material was due to a hopping process. This work aims to reveal the thermal properties of a new copper(II) based organic–inorganic hybrid and the conductivity properties that these compounds exhibit.     

Preparation of high surface area mesoporous nickel oxides and catalytic oxidation of toluene and formaldehyde

Mesoporous nickel oxide (NiO) nanoparticles were synthesized by the thermal decomposition reaction of Ni(NO₃)₂·9H₂O using oxalic acid dihydrate as the mesoporous template reagent. The pore structure of nanocrystals could be controlled by the precursor to oxalic acid dihydrate molar ratio, thermal decomposition temperature and thermal decomposition time. The structural characteristic and textural properties of resultant nickel oxide nanocrytals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N₂ adsorption–desorption isotherm and temperature programmed reduction. The results showed that the most excellently mesoporous nickel oxide particles (m-Ni-1-4) with developed wormlike pores were prepared under the conditions of the mixed equimolar precursor and oxalic acid and calcined for 4 h at 400 °C. The specific surface area and pore volume of m-Ni-1-4 are 236 m² g^?1 and 0.42 cm³ g^?1, respectively. Over m-Ni-1-4 at space velocity = 20,000 mL g^?1 h^?1, the conversions of toluene and formaldehyde achieved 90 % at 242 and 160 °C, respectively. It is concluded that the reactant thermal decomposition with oxalic acid assist is a key step to improve the mesoporous quality of the nickel oxide materials, the developed mesoporous architecture, high surface area, low temperature reducibility and coexistence of multiple oxidation state nickel species for the excellent catalytic performance of m-Ni-1-4.     

Effect of Sodium Carbonate on the Cloud Point in Alkyl Ether/Brine Systems: Apparent Relation with Dynamic Interfacial Tension Minimum

The effect of Na₂CO₃ on the cloud point in Na₂CO₃/surfactant/brine was investigated using two series of nonionic surfactants, C₁₃EO _x and C₁₇EO _x . The cloud point, T _cp, was found to decrease linearly with increasing Na₂CO₃ concentration. This was attributed to Na⁺ and particularly to CO₃ ^2?salting-out effect. The slope a = dTcp/d[Na₂CO₃] became more and more negative as the degree of ethoxylation is increased, suggesting that the higher the number of ethylene oxide (EO) groups the stronger is the cloud point depression for a given increment in Na⁺and CO₃ ^2?ions in solution. This was also illustrated by the linear variation of ΔT _cp = T _cp,0 ? T _cp,[Na2CO3] with the surfactant degree of ethoxylation.     

New functional copolymers of <Emphasis Type="Italic">N</Emphasis>-acryloyl-<Emphasis Type="Italic">N</Emphasis>′-methyl piperazine and 2-hydroxyethyl methacrylate: synthesis,determination of reactivity ratios and swelling characteristics of gels

Copolymers of N-acryloyl-N′-methylpiperazine (AcrNMP) and 2-hydroxyethyl methacrylate (HEMA) were synthesized by free radical solution polymerization in dioxane at 70 ± 1 °C, using 2,2′-azobisisobutyronitrile (AIBN) as initiator. The copolymer compositions were analyzed by the methods of FTIR spectroscopy and elemental analysis. Both the method of analysis yielded results that agreed reasonably well. The monomer reactivity ratios of the copolymerization were determined by the linearization methods of Finemann–Ross (FR) and Kelen–Tüdös (KT). The reactivity parameter results derived using FTIR analysis showed that the copolymerization yielded mainly alternating structure with reactivity ratios, r ₁(AcrNMP) = 0.263 ± 0.011 and r ₂(HEMA) = 0.615 ± 0.097 by F–R method and r ₁ = 0.227 ± 0.074 and r ₂ = 0.53 ± 0.15 by KT method. Microstructure data calculated by the method of Igarashi also supports the alternating structure (tendency) of the copolymer. Crosslinked polymer gels of this system exhibited remarkably high swelling of more than 500% in water at ambient temperature.     

Solid-phase synthesis and characterization of rare-earth chromates

Simple chromates(V) MCrO₄ (M = Sc, Y, Gd, Er, or Yb) and chromate(V) vanadates Gd(CrO₄) _x (VO₄)_{1 ? x} have been synthesized by a solid-phase method. All compounds crystallize in the xenotime-type structure, space group I4₁/amd, Z = 4. The unit cell parameters have been calculated as follows: for GdCrO₄, a = 7.209(5) Å, c = 6.318(4) Å; for ErCrO₄, a = 7.088(2) Å, c = 6.231(1) Å; for YbCrO₄, a = 7.034(1) Å, c = 6.205(2) Å; for YCrO₄, a = 7.108(3) Å, c = 6.254(3) Å; and for ScCrO₄, a = 7.012(2) Å, c = 6.188(2) Å. Symmetry D _2d , established for the CrO₄ tetrahedron during the Rietveld structure refinement, is verified by IR spectroscopy. The MCrO₄ simple chromates are paramagnets; their magnetic moments range from 1.7 to 8.1 μ _B .     

Lipoprint Adequately Estimates LDL Size Distribution,but not Absolute Size,Versus Polyacrylamide Gradient Gel Electrophoresis

Recently, a new cost-effective and less labor-intensive technique termed the “lipoprint LDL system” was developed to measure LDL particle size. However, the agreement between lipoprint and previously validated techniques, such as polyacrylamide gradient gel electrophoresis (PGGE), has never been tested. Therefore, we measured LDL size by lipoprint and PGGE in 16 obese subjects at 4 different time points. Lipoprint significantly overestimated (P = 0.003) integrated LDL particle size by 1.1 ± 3.0 Å when compared to PGGE. As for distribution, there was good agreement between methods for the estimation of large, medium, and small particles (mean difference between the methods was <3% for each parameter). Correlational analysis also revealed good relationships between methods for the proportion of large (r = 0.81, P < 0.0001), medium (r = 0.67, P < 0.0001), and small (r = 0.73, P < 0.0001) particles. In sum, although there is good agreement between lipoprint and PGGE for the determination of LDL size distribution, absolute LDL size values may differ between the two methods.     

Structure of a catalytically active oxo-centered trinuclear cobalt complex triaqua-(μ<Subscript>3</Subscript>-oxo)-hexa(μ<Subscript>2</Subscript>-pivalato-O,O′)-tricobalt(III)

The structure of a catalytically active oxo-centered trinuclear cobalt complex, namely, [triaqua-(μ₃-oxo)-hexa(μ₂-pivalato-O,O′)-tricobalt(III)]¹⁺ · NO ₃ ^? · 3H₂O, has been determined using X-ray diffraction analysis. The compound crystallizes in the hexagonal crystal system, space group of symmetry P6₃/mmc, with the unit cell parameters a = 12.328(1) Å, c = 22.625(1) Å, V = 2978.1(4) ų, Z = 2, and ρ = 1.075 g/cm³. The final discrepancy factor is R1 = 0.0596 for 589 symmetrically nonequivalent reflections with I ? 2σ(I), wR2 = 0.1612, and GooF = 1.035. The high-symmetry complex [C₃₀H₆₀O₁₆Co₃]¹⁺ with symmetry D _6h and a diameter of ～11 Å is an oxo-centered trinuclear cluster consisting of three symmetrically equivalent Co(III) atoms. Among the oxo-centered trinuclear metal complexes known to date, this complex has the highest symmetry and differs by the presence of two chemically equivalent bridges between the metal atoms. Apart from the two positively charged symmetrically equivalent trinuclear complexes, the unit cell contains two symmetrically equivalent NO ₃ ^? ions (statistically disordered over four positions) and six crystal water molecules.     

Surface-initiated growth of copper using isonicotinic acid-functionalized aluminum oxide surfaces

Isonicotinate self-assembled monolayers (SAM) were prepared on alumina surfaces (A) using isonicotinic acid (iNA). These functionalized layers (iNA-A) were used for the seeded growth of copper films (Cu-iNA-A) by hydrazine hydrate-initiated electroless deposition. The films were characterized by scanning electron microscopy (SEM), electron-dispersive X-ray spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and advancing contact angle measurements. The films are Cu⁰ but with surface oxidation, and show a faceted morphology, which is more textured (R _q = 460 ± 90 nm) compared to the SAM (R _q = 2.8 ± 0.5 nm). In contrast, growth of copper films by SnCl₂/PdCl₂ catalyzed electroless deposition, using formaldehyde (CH₂O) as the reducing agent, shows a nodular morphology on top of a relatively smooth surface. No copper films are observed in the absence of the isonicotinate SAM. The binding of Cu²⁺ to the iNA is proposed to facilitate reduction to Cu⁰ and create the seed for subsequent growth. The films show good adhesion to the functionalized surface.     

Synthesis and crystal structure of a new oxohalide CdPb<Subscript>2</Subscript>O<Subscript>2</Subscript>Cl<Subscript>2</Subscript>

A new compound, CdPb₂O₂Cl₂, is synthesized by the method of solid-phase reactions. The compound has monoclinic symmetry, space group C2/m, a = 12.392(8) Å, b = 3.8040(14) Å, c = 7.658(5) Å, β = 122.64(5)°, and V = 304.0(3) ų. The structure contains one symmetrically independent position of the Pb²⁺ cation coordinated by three O^2? anions (Pb²⁺-O^2? = 2.29–2.34 Å) and five Cl^? anions (Pb²⁺-Cl^? = 3.35–3.57 Å). The Cd²⁺ cation has a symmetric coordination with the formation of two bonds Cd-O = 2.15 Å and four bonds Cd-Cl = 2.73 Å. The oxygen atom is tetrahedrally coordinated by three Pb²⁺ cations and one Cd²⁺ cation, which leads to the formation of oxo-centered heterometallic OPb₃Cd tetrahedra. The tetrahedra are linked together into chains through common Pb atoms and into layered complexes due to sharing of the equatorial Cd atoms. The chlorine atoms are located above the cavities of the oxo-centered layer.     

Syntheses and Structural Characterization of Co(II) Coordination Polymers Supported by Bis(<Emphasis Type="Italic">N</Emphasis>-benzimidazolyl)methane and Bis(<Emphasis Type="Italic">N</Emphasis>-imidazolyl)methane

[Co₂(L¹)₂(NCS)₄]·4MeOH 1, [Co(L²)₂(H₂O)₂](Sal)₂·4H₂O (Sal = salicylate) 2 were obtained from self-assembly of the cobalt salts with bis(N-benzimidazolyl)methane (L¹), and bis(N-benzimidazolyl)methane (L²), and their structures were characterized by IR and X-ray diffraction analysis. Complex 1 exhibits a two-dimensional grid structure, whereas complex 2 is a coordination polymer having a one-dimensional linear chain structure. The grid in 1 lies parallel to the crystallographic ab plane and exhibits intra-grid M–M separations of 10.508 × 10.508 Å. Hydrogen bonds hold the cationic chains in 2 together leading to a three-dimensional network structure.     

Synthesis,Structures, and Catalytic Properties of Two Zinc(II) Coordination Polymers Constructed from Polycarboxylate and Bis(Benzimidazole) Ligands

Two Zn(II) coordination polymers, formulated as {[Zn(L1)_0.5(btc)_0.5(H₂O)]·H₂O} _n (1) and {[Zn(L2)(1,4-ndc)]·2H₂O} _n (2) [L1 = 1,4-bis(2-methylbenzimidazole-1-ylmethyl)benzene, L2 = 1,4-bis(2-methylbenzimidazole)butane, H₄btc = butane-1,2,3,4-tetracarboxylic acid, 1,4-H₂ndc = 1,4-naphthalenedicarboxylic acid] have been synthesized and structurally characterized by single crystal X-ray diffraction. Complex 1 features a 3D (3,4)-connected network with the topology of fsh-3,4-P2₁/c. Complex 2 is a 2D (4,4) grid with sql topology and further extends into a 3D supramolecular framework by π–π stacking interactions. In addition, the thermal stability, fluorescence, and catalytic properties of two complexes for degrading methyl orange dye in a Fenton-like process were investigated.     

Comparison of dye degradation potential of biosynthesized copper oxide,manganese dioxide,and silver nanoparticles using <Emphasis Type="Italic">Kalopanax pictus</Emphasis> plant extract

Copper(II) oxide (CuO), manganese dioxide (MnO₂), and silver (Ag) nanoparticles were synthesized using Kalopanax pictus plant extract. The nanoparticle synthesis was monitored using UV-visible spectra. The occurrence of each peak at 368, 404, and 438 nm wavelength indicated the synthesis of CuO, MnO₂, and Ag nanoparticles, respectively. The synthesized nanoparticles were characterized by X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. Catalytic potentials of the synthesized nanoparticles were compared to degrade two typical acidic and basic dyes (Congo red and Safranin O). The degradation ability of MnO₂ nanoparticles against Congo red was higher than that of Ag and CuO nanoparticles. All three types of nanoparticles showed a similar degradation ability against Safranin O over 80%. This study demonstrates that biologically synthesized nanoparticles using Kalopanax pictus are good agents for degradation of dyes.     

A Comprehensive Study on the Synthesis and Micellization of Disymmetric Gemini Imidazolium Surfactants

Two groups of disymmetric Gemini imidazolium surfactants, [C₁₄C₄C _m im]Br₂ (m = 10, 12, 14) and [C _m C₄C _n im]Br₂ (m + n = 24, m = 12, 14, 16, 18) surfactants, were synthesized and their structures were confirmed by ¹H NMR and ESI–MS spectroscopy. Their adsorption at the air/water interface, thermodynamic parameters and aggregation behavior were explored by means of surface tension, electrical conductivity and steady-state fluorescence. A series of surface activity parameters, including cmc, γ _cmc, π _cmc, pC ₂₀, cmc/C ₂₀, Γ _max and A _min, were obtained from surface tension measurements. The results revealed that the overall hydrophobic chain length (N _c) for [C₁₄C₄C _m im]Br₂ and the disymmetry (m/n) for [C _m C₄C _n im]Br₂ had a significant effect on the surface activity. The cmc values decreased with an increase of N _c or m/n. The thermodynamic parameters of micellization (ΔG _m ^θ , ΔH _m ^θ , ΔS _m ^θ ) derived from the electrical conductivity indicated that the micellization process of [C₁₄C₄C _m im]Br₂ and [C _m C₄C _n im]Br₂ was entropy-driven at different temperatures, but the contribution of ΔH _m ^θ to ΔG _m ^θ was enhanced by increasing N _c or m/n. The micropolarity and micellar aggregation number (N _agg) were estimated by steady-state fluorescence measurements. The results showed that the surfactant with higher N _c or m/n can form larger micelles, due to a tighter micellar structure.     

Catalytic Cu(II)–polymer complexes as recyclable catalysts for the synthesis of poly(2,6-dimethyl-1,4-phenylene oxide)s in water

Water-soluble polymers comprising itaconic amide acid with acrylic acid or acrylamide, which contain carboxylic acid and amide groups capable of coordinating to the copper catalyst, were synthesized by radical polymerization using an azobisisobutyronitrile initiator. These polymers were used as polymer ligands to prepare copper complexes, which were subsequently analyzed by UV–Vis spectroscopy. The complexes were then used as catalysts for the oxidative polymerization of 2,6-dimethylphenol (DMP) to synthesize poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) under oxygen and in the presence of a surfactant in alkaline water. The polymerization conditions were optimized by varying the amounts of polymer ligands and copper precursors, the concentrations of surfactant and hydrogen chloride, and the temperature, resulting in PPO with a maximum yield of 93%, a number-average molecular weight (M _n) of 3700, and a molecular weight distribution (M _w/M _n) of 2.12. This yield is higher than that previously achieved using arginine ligand in water (72%). Furthermore, the optimum conditions were applied in the copolymerization of DMP and 2-allyl-6-methylphenol to obtain a thermally crosslinkable copolymer in 95% yield (M _n = 3000, M _w/M _n = 2.5). In addition, the catalyst complex of the copper–polymer ligand was recovered and reused after the polymerization of DMP. The catalyst maintained its activity even after being recycled five times, without the addition of copper precursor or polymer ligand, thereby demonstrating an environmentally friendly process wherein environmental emissions and production costs can be substantially reduced.     

Seasonal N<Subscript>2</Subscript>O emissions respond differently to environmental and microbial factors after fertilization in wheat–maize agroecosystem

Biogeochemical processes regulating cropland soil nitrous oxide (N₂O) emissions are complex, and the controlling factors need to be better understood, especially for seasonal variation after fertilization. Seasonal patterns of N₂O emissions and abundances of archaeal ammonia monooxygenase (amoA), bacterial amoA, nitrate reductase (narG), nitrite reductase (nirS/nirK), and nitrous oxide reductase (nosZ) genes in long-term fertilized wheat–maize soils have been studied to understand the roles of microbes in N₂O emissions. The results showed that fertilization greatly stimulated N₂O emission with higher values in pig manure-treated soil (OM, 2.88 kg N ha^?1 year^?1) than in straw-returned (CRNPK, 0.79 kg N ha^?1 year^?1) and mineral fertilizer-treated (NPK, 0.90 kg N ha^?1 year^?1) soils. Most (52.2–88.9%) cumulative N₂O emissions occurred within 3 weeks after fertilization. Meanwhile, N₂O emissions within 3 weeks after fertilization showed a positive correlation with narG gene copy number and a negative correlation with soil NO₃^? contents. The abundances of narG and nosZ genes had larger direct effects (1.06) than ammonium oxidizers (0.42) on N₂O emissions according to partial least squares path modeling. Stepwise multiple regression also showed that log narG was a predictor variable for N₂O emissions. This study suggested that denitrification was the major process responsible for N₂O emissions within 3 weeks after fertilization. During the remaining period of crop growth, insufficient N substrate and low temperature became the primary limiting factors for N₂O emission according to the results of the regression models.     

Perovskite-type MgCNi<Subscript>3</Subscript> superconductors as prepared by combined sintering-ETE process and SHS reaction: Structural and superconducting properties

Complete conversion of the elements into the Perovskite-type MgCNi₃ compound has been achieved in the following two-stage process: (1) isothermal treatment (sintering) of starting powder compacts and (2) their subsequent electrothermal explosion (ETE) under uniaxial pressure. For comparison, similar reaction was also performed by mere sintering and by SHS. The bulk anti-perovskite MgCNi₃ superconductor was prepared from Mg-C-3Ni powder compacts. Isothermal treatments failed in the formation of the perovskite-type compound as a sole product. The hexagonal MgCNi₃ phase obtained by combined sintering-ETE route was found to have the lattice constants a = 3.0845 Å and c = 3.5259Å. The grains of the MgCNi₃ obtained by sintering-ETE process are fine, well compacted, and more homogenous than those prepared by sintering or SHS. The structure of materials was characterized by XRD, SEM, and EDS. The superconducting properties were detected using the temperature dependence of magnetization M as measured in ZFC and FC experiments at H = 15 Oe. For our MgCNi₃, the superconducting transition temperature T _c is around 7 K.     

Synthesis and Characterization of Novel Aryl Alkyl Sulfonates Based on Nonylphenol

A series of nonylphenol-substituted alkyl sulfonates (C _x NPAS, x = 8, 10, 12, 14, 16) with two hydrocarbon chains and two different hydrophilic groups has been synthesized from α-olefins and nonylphenol. The respective products have a “pseudo-gemini” surfactant structure. The structures of the C _x NPAS have been characterized by IR, UV, ¹H nuclear magnetic resonance, electrospray ionization mass spectrometry, and elemental analysis. The effects of carbon chain length of the obtained surfactants on properties such as the critical micelle concentrations (CMC) in aqueous solutions, surface tension at the CMC (γ _CMC), and efficiency of adsorption at the water/air interface (pC ₂₀) have been determined. The γ _CMC of the surfactants first decreased and then increased with increasing length of the carbon chain x, and reached a minimum of 29.25 mN/m at x = 10, which is much lower than that of α-olefin sulfonate (AOS) (33.52 mN/m). The CMC decreased and pC ₂₀ increased with increasing x. The introduction of the hydroxyl group is responsible for multiple molecular conformations at the water/air interface and leads to a greater molecular area A _min and smaller Γ_max than those of AOS.