Improved hydrolytic stability of poly(dl-lactide) with epoxidized soybean oil

The multi-arm star polymer (ESOPLA) was obtained by ring-opening polymerization of dl-lactide using multifunctional epoxidized soybean oil (ESO) as an initiator in the presence of a stannous actuate (SnOct₂) catalyst. Gel permeation chromatography with multi-angle laser light scattering (GPC-MALLS), FTIR, ¹H NMR, thermal analysis and in vitro degradation were used to qualitatively characterize the synthesized polymers. The results revealed that ESO plays an important role in increasing the molecular weight, polymerization rate and monomer conversion rate. Degradation analysis demonstrated that the decrease in molecular weight and the weight loss ratio of the star-shaped ESOPLA were lower than that of linear poly(dl-lactide) (PDLLA). The surface topography of pre- and post-degradation materials was characterized by scanning electron microscopy (SEM). These SEM images showed that the linear PDLLA films underwent water erosion more readily than the star-shaped polymer films.     

A new flavonoid from <Emphasis Type="Italic">Macrothelypteris torresiana</Emphasis>

A new flavonoid, 5,7-dihydroxy-2-(1-hydroxy-2,6-dimethoxy-4-oxo-cyclohex)-chromen-4-one (1), was isolated from the roots of Macrothelypteris torresiana (Gaud.) Ching. (Thelypteridaceae). The structure of the product was identified on the basis of detailed spectral analysis, including X-ray structure analysis.     

Culture of Microalgae <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> in Wastewater for Biomass Feedstock Production

The objective of this research was to develop large-scale technologies to produce oil-rich algal biomass from wastewater. The experiments were conducted using Erlenmeyer flasks and biocoil photobioreactor. Chlamydomonas reinhardtii was grown in artificial media and wastewaters taken from three different stages of the treatment process, namely, influent, effluent, and centrate. Each of wastewaters contained different levels of nutrients. The specific growth rate of C. reinhardtii in different cultures was monitored over a period of 10 days. The biomass yield of microalgae and associated nitrogen and phosphorous removal were evaluated. Effects of CO₂ and pH on the growth were also studied. The level of nutrients greatly influenced algae growth. High levels of nutrients seem to inhibit algae growth in the beginning, but provided sustained growth to a high degree. The studies have shown that the optimal pH for C. reinhardtii is in the range of 7.5. An injection of air and a moderate amount of CO₂ promoted algae growth. However, too much CO₂ inhibited algae growth due to a significant decrease in pH. The experimental results showed that algal dry biomass yield reached a maximum of 2.0 g L⁻¹ day⁻¹ in the biocoil. The oil content of microalgae of C. reinhardtii was 25.25% (w/w) in dry biomass weight. In the biocoil, 55.8 mg nitrogen and 17.4 mg phosphorus per liter per day were effectively removed from the centrate wastewater. Ferric chloride was found to be an effective flocculent that helps the algae settle for easy harvest and separation from the culture media.     

Highly sensitive naked-eye and fluorescence "turn-on" detection of Cu(2+) using Fenton reaction assisted signal amplification

Increase of pH induced by Cu(2+)-catalyzed Fenton reaction promoted ring-opening of triazole-linked fluorescein lactone, which enabled selective "turn-on" fluorescent detection of Cu(2+), along with ultralow naked-eye detection limit down to 200 nM.     

A Flexible Approach to Azasugars: Asymmetric Total Syntheses of (+)‐Castanospermine, (+)‐7‐Deoxy‐6‐epi‐castanospermine,and (+)‐1‐epi‐Castanospermine

The asymmetric total synthesis of natural azasugars (+)‐castanospermine, (+)‐7‐deoxy‐6‐epi‐castanospermine, and synthetic (+)‐1‐epi‐castanospermine has been accomplished in nine to ten steps from a common chiral building block (S)‐ 8 . The method features a powerful chiral relay strategy consisting of a highly diastereoselective vinylogous Mukaiyama‐type reaction with either chiral or achiral aldehydes (≥95 % de; de=diastereomeric excess) and a diastereodivergent reduction of tetramic acids, which allows formation of three continuous stereogenic centers with high diastereoselectivities. The method also provides a flexible access to structural arrays of 5‐(α‐hydroxyalkyl)tetramic acids, such as 17/34 , and 5‐(α‐hydroxyalkyl)‐4‐hydroxyl‐2‐pyrrolidinones, such as 18 and 25/35 a . The method constitutes the first realization of the challenging chiral synthons A and D and thus of the conceptually attractive retrosynthetic analysis shown in Scheme 1 in a highly enantioselective manner.     

Inverse transient radiation analysis in one-dimensional non-homogeneous participating slabs using particle swarm optimization algorithms

Particle Swarm Optimization (PSO) algorithms, including standard PSO, Stochastic PSO, and Multi-Phase PSO, are applied to solve the time-domain inverse transient radiation problems in the present research. Time-resolved transmittance and reflectance signals of four different measuring models serve as the measurement data, which estimate absorption, scattering coefficients, and geometric position within one-dimensional non-homogeneous media by inverse simulation. To check retrieval performances and accuracies of PSO-based approaches, four different inverse transient radiation cases are investigated to deal with one homogeneous layer, two-layer, three-layer, and continuous non-homogenous media. The influences of different searching ranges, swarm sizes, and maximum fly velocities on the fitness function of PSO are discussed. Meanwhile, the effects of measurement errors on the reconstruction accuracy are also investigated. All the results confirm that radiative parameters could be estimated accurately with measurement noise using PSO-based approaches.     

Mixing layer height and meteorological measurements in Hefei China during the total solar eclipse of 22 July, 2009

Mixing layer height measurements with an elastic-backscattered lidar were carried out in Hefei, China, during the total solar eclipse of 22 July, 2009. The mixing layer height evolution is studied with the observation of changes in near-ground temperature, relative humidity and wind speed. The lidar emits the laser at the wavelengths of 532 and 355 nm, respectively, and obtains the backscattered signal with the resolution of 10 m. The whole eclipse witnessed the mixing layer change similar to that occurring during sunset. The results also show the mixing layer height decreased to 287 m rapidly during the total eclipse within only more than 1 min from the initial 354 m. The entrainment thickness reached the minimum of 43 m in the eclipse, indicating the weakening of the penetrative convection. Thereafter the thickness kept a constant value of 180 m. The temperature in the whole eclipse is uptrend, increasing only by 0.5 °C as a whole. The wind speed decreased and simultaneously the wind direction changed. The wind speed reached its minimum of 2 m/s at the end of the eclipse.     

Efficient anti-stokes signal generation through degenerate four wave mixing in an all solid photonic bandgap fiber

We reported the generation of visible red light through degenerate four wave mixing (FWM) in an all solid photonic bandgap fiber (PBGF), which was achieved by pumping the fiber with a 800 nm Ti:sapphire-based femtosecond pulse laser. At a fiber length of 30 m, a broadband anti-Stokes spectrum range from 620 nm to 740 nm was obtained at the highest pump power, the spectrum evolution as a function of pump power and propagation distance had been measured. Furthermore, the intensity-dependent parametric gain characteristic is also calculated, which accords well with the experimental results.     

Be(d,n)反应中子源能谱测量及应用

 利用中子飞行时间技术和BC501A液体闪烁探测器的粒子分辨特性,测量了0°方向、20 MeV氘束轰击厚金属铍靶反应产生的中子源能谱,测量的中子能谱范围为0.7～25.0 MeV。在60°方向放置芪晶体闪烁探测器,由刻度好的BC501A液体闪烁探测器归一校正后,用于中子源强度监测。利用Be(d, n) 反应中子源,采用单粒子灵敏度标定方法,实验标定了0.75~15.75 MeV能量范围内的薄膜闪烁探测器中子能量响应曲线,实验结果与蒙特卡罗模拟计算结果在8%的不确定度范围内一致。