Responses of soil respiration in non-growing seasons to environmental factors in a maize agroecosystem,Northeast China

Based on continuous three-year measurements (from 2004 to 2007) of eddy covariance and related environmental factors, envi-ronmental controls on variation in soil respiration (R_s) during non-growing season were explored in a maize agroecosystem in Northeast China. Our results indicated that during non-growing seasons, daily Rs was 1.08–4.08 g CO2 m^–2 d^–1, and the lowest occurred in late November. The average R_s of non-growing season was 456.06 ± 20.01 g CO2 m^–2, accounting for 11% of the gross primary production (GPP) of the growing season. Additionally, at monthly scale, the lowest value of R_s appeared in January or February. From the beginning to the end of non-growing season, daily R_s tended to decrease first, and then increase to the highest. There was a significant quadratic curve relationship between Rs and soil temperature at 10 cm depth when soil temperature was more than 0°C (P<0.001), with the explaining ratio of 38%–70%. When soil water content was more than 0.1 m³ m^–3, soil moisture at 10 cm depth was significantly parabolically correlated with R_s (P<0.001), explaining the rate of 18%–60%. Based on all the data of soil temperature of more than 0°C, a better model for R_s was established by coupling soil temperature and moisture, which could explain the rate of up to 53%–79%. Meanwhile, the standard error of regression estimation between the values of prediction and observation for R_s could reach 2.7%–11.8%. R_s in non-growing season can account for 22.4% of R_s in growing season, indicating that it plays a critical role in assessing the carbon budget in maize agroecosystem, Northeast China.     

A novel self-promoted Morita-Baylis-Hillman-like dimerization

While stable in CH₂Cl₂, hexane or THF, in the presence of MeOH, self-promoted dimerization of the triarylphosphine-alkene 1, a ligand for Pd-catalyzed reactions, produced an unusual racemic bis(phosphine) 2 in high yield. The reaction of 2 with Pd(dba)₂, followed by oxidative addition of p-IC₆H₄NO₂, yielded a trans-chelated Pd(II) aryl iodide complex.     

Solving surface plasmon resonances and near field in metallic nanostructures: Green’s matrix method and its applications

With the development of nanotechnology, many new optical phenomena in nanoscale have been demonstrated. Through the coupling of optical waves and collective oscillations of free electrons in metallic nanostructures, surface plasmon polaritons can be excited accompanying a strong near field enhancement that decays in a subwavelength scale, which have potential applications in the surface-enhanced Raman scattering, biosensor, optical communication, solar cells, and nonlinear optical frequency mixing. In the present article, we review the Green’s matrix method for solving the surface plasmon resonances and near field in arbitrarily shaped nanostructures and in binary metallic nanostructures. Using this method, we design the plasmonic nanostructures whose resonances are tunable from the visible to near-infrared, study the interplay of plasmon resonances, and propose a new way to control plasmonic resonances in binary metallic nanostructures.     

Advances in the hyperlens

As a superlens to overcome the well-known diffraction limit, the hyperlens has received much attention due to its super resolving power and magnifying capabilities. In this article, we review the recent developments, including theoretical and experimental studies on the hyperlens. We also discuss its limitations and potential.     

Infrared phononic nanoantennas: Localized surface phonon polaritons in SiC disks

The electromagnetic interaction of light with polar materials shows a sharp and well defined electromagnetic response in the infrared (IR) region that consists mainly of excitation of optical phonons. Similar to surface plasmons in the visible region, surface phonons can couple efficiently to infrared light in micron-sized antennas made of polar materials. We applied the boundary element method to calculating the infrared electromagnetic response of single SiC disks acting as effective infrared antennas as a function of different parameters such as disk size and thickness. We also analyzed the effect of locating a probing metallic tip near the SiC disk to scatter light in the proximity of the SiC disk, thereby obtaining new spectral peaks connected with localized modes between the tip and the SiC disk. We then further investigated their application in IR scanning probe microscopy. A near-field map of the phononic resonances enhances the understanding of the nature of the IR extinction peaks.     

Asymmetric synthesis of <Emphasis Type="Italic">Anomala Osakana</Emphasis> Pheromone isomer using protecting group free strategy

The protecting group free synthesis of Anomala Osakana Pheromone isomer has been achieved with high enantioselectivity (92% ee). A chiral γ-hydroxy-α, β-acetylenic ester was used as the key intermediate, which was obtained via asymmetric alkynylation of aldehyde. This was followed by readily handled selective hydrogenation and lactonization in three steps with a high overall yield (86%).     

A parallel approach to direct resolution of albuterol

A library consisting of a series of O,O′-diaryzoyl-L-(–)-tartaric acids (2) was designed and synthesized. The substituent on the aromatic ring of 2 significantly affects the diastereomeric excess and efficiency of the resolution of racemic albuterol (1). Excellent resolving reagent 2a was selected for the resolution of rac-1 via the parallel approach. However, a family of three resolving reagents failed to improve the resolution efficiency of rac-1.     

Synthesis of novel chiral bisoxazoline ligands with a spiro[4,4]-1,6-nonadiene skeleton

A new type of chiral bisoxazoline ligands 1 based on spiro[4,4]-1,6-nonadiene backbone was easily prepared in six steps from racemic spiro[4,4]-nonane-1,6-dione, with the Pd-catalyzed coupling of the enol triflates with CO and amino alcohols as the key steps for the construction of the oxazoline moiety. The structure of the ligand (R,S,S)-1b was unambiguously established by X-ray crystallographic analysis. The chiral Cu(II) complex generated in situ from the combination of spiro bisoxazoline ligand (S,S,S)- 1c and Cu(OTf)₂ was effective in the catalysis of asymmetric chlorination of the β-ketoester, methyl 1-oxo-2,3-dihydro-1H- in-dene-2-carboxylate, affording the corresponding chlorinated derivative in 99% yield with 17% ee.     

Diastereoselective addition of lithium enolate of γ-substituted α-diazoacetoacetate to <Emphasis Type="Italic">N</Emphasis>-sulfinyl imines

Highly diastereoselective addition of lithium enolate of γ-substituted α-diazoacetoacetate to chiral N-sulfinyl imines has been developed. The addition products were further subjected to photo-induced Wolff rearrangement or Rh(II)-catalyzed intramolecular N–H insertion to afford chiral 4,5-disubstituted 2-oxo and 3-oxo pyrrolidines, respectively.     

Seasonal variations and environmental controls on stalagmite calcite crystal growth in Heshang Cave,central China

Stalagmite growth rates are usually considered to reflect changes in paleoclimate and paleoenvironment. However, how exactly growth rates are affected by climate and environment is still unclear. We launched a monitoring and modeling program that lasted approximately 4 years on two active drip sites in Heshang Cave, central China. We collected comprehensive quantitative data on growth rates, cave temperature, CO₂ concentration, drip rate and drip-water chemistry to better understand the relationship between stalagmite growth and cave environment. By laying out glass substrates, we successfully grew stalagmite calcite crystals with rhombic characteristics, and quantified growth rates by measuring the long and short axes of calcite crystals under a microscope. Combined with coeval environmental data, we explicitly examined the roles of cave temperature, drip rate and drip-water chemistry in controlling the micro-scale growth of stalagmite calcite. Results show that growth of stalagmite calcite crystals at two drip sites exhibited similar seasonal variations − generally faster in the summer months, at ∼3 μm d⁻¹, and slower during the late winter to early spring, at ∼1.5 μm d⁻¹. Variations in calcite growth rates were mainly determined by changes in cave temperature, with the growth rate increasing by 8.1%/°C and 6.6%/°C at the two locations. This indicates the potential use of stalagmite growth rates as a seasonal-resolution paleo-temperature proxy in some ventilated caves. On the other hand, the effect of drip rate and drip-water Ca²⁺ and SIC values on growth rates were not significant.