ALBERT

Description: [1]  A body of revolution, finite-difference time-domain (BOR-FDTD) method is developed for rigorous analysis of axisymmetric transformation optics (TO) lens devices. For normal incidence, a one dimensional (1-D) FDTD method based on the total-field scattered-field (TFSF) technique was proposed to model the propagation of a plane wave launched from the top of a layered medium in cylindrical coordinates. The 1-D FDTD solutions were employed to efficiently inject normally-incident plane waves into the BOR-FDTD method. For oblique incidence, analytical formulations were derived and presented by expanding the plane wave into a series of cylindrical modes via Fourier series expansion of the ϕ-dependent variables, which were then used to introduce obliquely-incident plane waves into the TFSF formulas associated with the BOR-FDTD method. These procedures allowed for accurate simulations of BOR TO lenses embedded in layered media illuminated by obliquely incident waves. The accuracy and efficiency of the proposed method were verified by comparing numerical results with either analytical solutions or a commercial software (COMSOL) package. Thereafter, the developed BOR-FDTD code was utilized to study the imaging properties of (a) radial gradient-index (GRIN) lenses with a parabolic index profile, (b) a flat TO GRIN lens, (c) a spherical Luneburg lens, and (d) a cylindrical TO Luneburg lens both in free space and on top of a substrate. Here, the TO GRIN lenses were designed by using the quasi-conformal transformation optics (QCTO) technique. It was found that the flat TO lens was able to provide identical focusing properties as a cemented doublet in both free space and over a dielectric substrate. Moreover, the numerical results demonstrated that the flattened TO Luneburg lens possessed the desired imaging properties under different illuminations for both polarizations.

Description: To reveal the relative contribution of labile carbon (LC) limitation and soil microbial community responses in attenuating the effect that extended warming has on soil heterotrophic respiration (Rh), soil samples from Tibetan grasslands were exposed to an initial incubation (Experiment 1). Subsequently, soils were sterilized then inoculated with parent soil microbes to assess the LC limitation effects (Experiment 2) or soil microbes from the incubations were used to inoculate sterilized parent soils to assess the microbial community effects (Experiment 3). Both LC limitation and microbial community responses led to significant declines in Rh by 37% and 30%, respectively. Abstract Changes in labile carbon (LC) pools and microbial communities are the primary factors controlling soil heterotrophic respiration (Rh) in warming experiments. Warming is expected to initially increase Rh but studies show this increase may not be continuous or sustained. Specifically, LC and soil microbiome have been shown to contribute to the effect of extended warming on Rh. However, their relative contribution is unclear and this gap in knowledge causes considerable uncertainty in the prediction of carbon cycle feedbacks to climate change. In this study, we used a two‐step incubation approach to reveal the relative contribution of LC limitation and soil microbial community responses in attenuating the effect that extended warming has on Rh. Soil samples from three Tibetan ecosystems—an alpine meadow (AM), alpine steppe (AS), and desert steppe (DS)—were exposed to a temperature gradient of 5–25°C. After an initial incubation period, soils were processed in one of two methods: (a) soils were sterilized then inoculated with parent soil microbes to assess the LC limitation effects, while controlling for microbial community responses; or (b) soil microbes from the incubations were used to inoculate sterilized parent soils to assess the microbial community effects, while controlling for LC limitation. We found both LC limitation and microbial community responses led to significant declines in Rh by 37% and 30%, respectively, but their relative contributions were ecosystem specific. LC limitation alone caused a greater Rh decrease for DS soils than AMs or ASs. Our study demonstrates that soil carbon loss due to Rh in Tibetan alpine soils—especially in copiotrophic soils—will be weakened by microbial community responses under short‐term warming.

Description: Gd2O2S:Tb nanophosphor with favorable dispersion and high chemical/phase purity was obtained via a low temperature precipitation approach. Abstract Titrating the aqueous solution of equimolar RE(NO3)3 and (NH4)2SO4 with NH4OH to pH~9 at ~4°C produced an amorphous precursor that yielded phase‐pure and well‐dispersed RE2O2S nanopowder (RE = Gd0.99Tb0.01; GOS:Tb) via a RE2O2SO4 intermediate upon annealing in H2. The powders calcined at the typical temperatures of 700/1200°C exhibited unimodal size distributions and have the average crystallize sizes of ~17/55 nm, average particle sizes of ~284/420 nm, and specific surface areas of ~14.62/4.53 m2/g (equivalent particle sizes: ~56/180 nm). The 1200°C product exhibited sharp green luminescence at ~544 nm (FWHM = 2.3 nm; λex = 275 nm), with an absolute quantum yield of ~24.8% and a fluorescence lifetime of ~1.34 ms at room temperature. It was also shown that the powder possesses favorable thermal stability (the activation energy for thermal quenching of luminescence ~0.305 eV) and is stable under electron beam irradiation up to 7 kV and 50 μA. The synthetic technique has the advantages of scalability and favorable dispersion and high chemical/phase purity for GOS powder, which may allow the sintering of scintillation ceramics at lower temperatures.

Description: Abstract Hydrothermal reaction at 150°C and pH = 10 for 24 hours crystallized (Gd,RE)2(OH)4SO4 layered hydroxide sulfate (monoclinic structure; RE = Pr, Tb), from which Gd2O2S:RE (hexagonal structure) green phosphor hexagons were derived via facile dehydration in flowing H2 at 1200°C. Rietveld refinement of the XRD patterns yielded cell dimensions that confirmed the direct crystallization of solid solution. Photoluminescence (PL) study at room temperature found absolute quantum yields of ~25.1% and 28.4%, CIE chromaticity coordinates of (0.145, 0.679) and (0.326, 0.566), and fluorescence lifetimes of ~2.36 μs and 1.21 ms for Pr3+ and Tb3+ under 300 and 275 nm UV excitations, respectively. Temperature‐dependent PL analysis (25‐200°C) indicated that both the Pr3+‐ and Tb3+‐doped phosphors have favorably good thermal stability and retained ~65% and 80% at 100°C and ~41% and 47% at 200°C of their initial emission intensities, respectively. The activation energy for the thermal quenching of PL was determined to be ~0.221 (Pr3+) and 0.314 eV (Tb3+). Cathodoluminescence (CL) found that both the phosphors exhibit increasingly higher emission intensity/brightness at a higher acceleration voltage (up to 7 kV) or beam current (up to 50 μA) and are stable under electron bombardment in the studied range. Raising beam current was suggested to be more effective to enhance CL.

Description: The new secoiridoid sulfonates 1 – 3 were isolated from the 50% EtOH/H 2 O extract of the sulfiting-processed Lonicera japonica Flos ( LJF ) by semi-prep. HPLC, and their structures were identified on the basis of mass spectrometry and NMR spectroscopy. HPLC and LC-DAD-MS/MS analyses of the different samples of LJF obtained by various process techniques suggested that the sulfur fumigation led to the decrease of secologanic acid ( 4 ) and the formation of secologanic acid-derived sulfonate 1 and its derivatives 2, 2a , and 3 in the crude materials, which revealed that sulfur fumigation, the traditional process technique, could alter the phytochemical profiles of some Chinese herbal medicines.

Description: River confluences and their associated tributaries are key morphodynamic nodes that play important roles in controlling hydraulic geometry and hyporheic water exchange in fluvial networks. However, the existing knowledge regarding hyporheic water exchange associated with river confluence morphology is relatively scarce. On the 14 th and 15 th of January, 2016, the general hydraulic and morphological characteristics of the confluent meander bend (CMB) between the Juehe River and the Haohe River in the southern region of Xi’an City, Shaanxi Province, China were investigated. The patterns and magnitudes of vertical hyporheic water exchange (VHWE) were estimated based on a one-dimension heat steady-state model while the sediment vertical hydraulic conductivity ( K v ) was calculated via in situ permeameter tests. The results demonstrated that six hydrodynamic zones and their extensions were observed at the CMB during the test period. These zones were likely controlled by the obtuse junction angle and low momentum flux ratio, influencing the sediment grain size distribution of the CMB. The VHWE patterns at the test site during the test period mostly showed upwelling flow dominated by regional groundwater discharging into the river. The occurrence of longitudinal downwelling and upwelling patterns along the meander bend at the CMB was likely subjected to the comprehensive influences of the local sinuosity of the meander bend and regional groundwater discharge, and finally formed regional and local flow paths. Additionally, in dominated upwelling areas, the change in VHWE magnitudes was nearly consistent with that in K v values, and higher values of both variables generally occurred in erosional zones near the thalweg paths of the CMB, which were mostly made up of sand and gravel. This was potentially caused by the erosional and depositional processes subjected to confluence morphology. Furthermore, lower K v values observed in downwelling areas at the CMB were attributed to sediment clogging caused by local downwelling flow. The confluence morphology and sediment K v are thus likely the driving factors which cause local variations in the VHWE of fluvial systems.

Description: In this paper, reanalysis data collected by ERA-Interim 4 times daily from 1979-2014 are used to analyze the main atmospheric moisture sources of cumulative effect of torrential rain (CETR) events during the preflood season (April 1 to June 30) over South China. Using a Lagrangian particle dispersion model—the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model—the major atmospheric moisture sources of 66 CETR events for the period 1979-2014 are identified and compared. In this study, five atmospheric moisture sources—the land area (LD), Indian Ocean (IO), Pacific Ocean (PO), South China Sea (SCS), and South China (SC)—are defined, and the effects of these moisture sources on preflood season CETR events over South China are quantitatively estimated. The results indicate that during the preflood season, Indian Ocean water vapor transport accounts for 30% of the atmospheric moisture generated in CETR events, thus dominating precipitation over South China. The water vapor transport from the land area (14%), western Pacific Ocean (10%), South China Sea (25%), and South China (20%) also play important roles in preflood season CETR events. Furthermore, a significant transition in water vapor transport occurred in the 1990s, during which water vapor transport from the Indian Ocean increased significantly, while water vapor transport from the western Pacific Ocean significantly declined. In addition, a significant positive anomaly in Pacific Ocean and South China Sea water vapor transport spurred CETR events in the east, while a significant positive anomaly in Indian Ocean water vapor transport facilitated CETR events in the west.

Description: In the present study, ceramic supported copolyimide membranes were synthesized via the two-step thermal imidization method and applied to pervaporation recovery of amide solvents including dimethylformamide (DMF) and dimethylacetamide (DMAc). The prepared membrane demonstrated high resistant to the two amides under a wide range of concentration. Moreover, effects of operating parameters such as feed temperature, feed concentration on pervaporation performances of the membrane were investigated. The copolyimide membrane displayed optimum permeation flux of 210 and 402 g m −2 h −1 with corresponding separation factors of 66 and 175, respectively, for H 2 O/DMF and H 2 O/DMAc mixtures with a water concentration of 20 wt % at 333 K.

Description: In present study, a Cecropin-like peptide from Antheraea pernyi ( Ap Cec) was cloned and characterized. The full-length Ap Cec cDNA encoded a protein with 64 amino acids including a putative 22-amino-acid signal peptide, a 4-amino-acid propeptide, and a 38-amino-acid mature peptide. Ap Cec gene was highly expressed in Malpighian tubules of A. pernyi after induction for 24 h by Escherichia coli in PBS. Pro- Ap Cec (including propeptide and mature peptide) and M- Ap Cec (just mature peptide) were synthesized chemically and analyzed by HPLC and mass spectroscopy. The antibacterial activity of M- Ap Cec is more potent than pro- Ap Cec against E. coli K12 or B. subtilus in both minimum inhibitory concentration and inhibition zone assays. Hemolytic assay results showed M- Ap Cec possessed a low cytotoxicity to mammalian cells. The secondary structure of M- Ap Cec forms α-helical structure, shown by circular dichroism spectroscopy. Transmission electron microscopy analysis suggested that M- Ap Cec killed bacteria by disrupting bacterial cell membrane integrity. Our results indicate Ap Cec may play an important role in defending from pathogenic bacteria in A. pernyi , and it may be as a potential candidate for applications in antibacterial drug development and agriculture.