ISSN 0253-2778

CN 34-1054/N

2018 Vol. 48, No. 7

Display Method:
Short cationic peptides induce pH-sensitive non-leaky membrane fusion
WANG Fengyu, HUI Liwei, XU Lulu, GAO Feng, ZHAO Zhi, YANG Lihua
2018, 48(7): 519-526. doi: 10.3969/j.issn.0253-2778.2018.07.001
pH-sensitive,non-leaky and complete membrane fusion mediated by two short peptides is shown. Depending on the specific fusogenic peptides,the observed fusion occurs at different pH ranges.
Dissociation dynamics of o-, p-, m-C7H7Br+ ions in the 8.5~12.5 eV energy range
XIA Yu, TANG Xiaofeng, WEN Zuoying, WU Xiangkun, WANG Chengcheng, GUO Xiaotian, LIU Fuyi, ZHANG Weijun
2018, 48(7): 527-534. doi: 10.3969/j.issn.0253-2778.2018.07.002
The photoionization and dissociative photoionization of o-, p-, m-bromotoluene were investigated by utilizing synchrotron-based threshold photoelectron photoion coincidence spectroscopy (TPEPICO). Threshold photoelectron spectra (TPES), TPEPICO mass spectra and mass-selected TPEPICO spectra corresponding to each species were measured in the 8.5~12.5 eV energy range. The fundamental data including the ionization energy of bromotoluene molecules and the appearance energy of the C7H7+ fragment ions are acquired and agree well with previous literature results. Then based on the obtained average kinetic energy released in the dissociation and the existing potential energy surfaces, the dissociation mechanisms of o-, p-, m-bromotoluene ions are proposed. The bromotoluene ions with small internal energy will dissociate to benzyl ions and Br atoms after performance of inter-conversion to isomers, whereas those with large internal energy will directly fragment to the tolyl ions via the C-Br bond breaking.
Biocatalytic hydroxylation of vitamin D3 in ionic liquid biphasic systems
CHENG Zhaopeng, TANG Dandan, XU Zhinan
2018, 48(7): 535-541. doi: 10.3969/j.issn.0253-2778.2018.07.003
To explore the biocatalytic hydroxylation of vitamin D3 catalyzed by Bacillus cereus HDZJU1-11 in ionic liquid biphasic systems, a comparison was conducted of the substrate solubility and biocompatibility in 5 ionic liquids ([PrMIm][PF6], [BMIm][PF6], [BMIm][NTf2], [HMIm][PF6], and [OMIm][NTf2]) and the optimization of phase ratio, pH, and substrate concentration in ionic liquid biphasic systems was performed. [BMIm][PF6], [BMIm][NTf2], and[OMIm][NTf2] were chosen to construct biphasic systems. In [BMIm][PF6]/water biphasic system, the optimal conversion condition is as follows: 0.5 mg/mL vitamin D3 and [BMIm][PF6] (Vwater∶VIL=4∶1) are added after 12 h fermentation of Bacillus cereus, and the pH of water phase is 7.5. The concentration of 25-hydroxyvitamin D3 is increased to 0.38 mg/mL at 24 h fermentation. The optimal conversion conditions in ionic liquid biphasic systems are determined, which lays a foundation for expanding experiment and industrial applications.
Effect ofmechanical activation and hydrostatic pressure on the crystal structure of brucite
WANG Yueqin, LIU Yin, ZHANG Mingxu, MIN Fanfei
2018, 48(7): 542-549. doi: 10.3969/j.issn.0253-2778.2018.07.004
Ultrafine brucite powder was prepared by the high energy ball-milling method with brucite mineral as raw material. The effect of ball-milling time on the lattice structure and the mean particle size was analyzed by X-ray diffraction(XRD),Fourier-transform infrared spectroscopy (FTIR) and laser particle(LP). The mechanism of different hydrostatic pressures on the crystal structure of brucite was studied by the first principles calculation. The experimental results show that the crystal structure is more easily distorted along the [001] direction with the mechanical activation, and that, with longer ball-milling the peaks of IR spectrum in brucite exhibit blue-shift and broadening, and the ultrafine brucite powder with the mean particle size of 3.56 μm is obtained after ball-milling for 3 h. The theoretical results show that the lattice constant a decreases linearly and c decreases nonlinearly as the hydrostatic pressure increases. The band gap increases with the increases in pressure, which is mainly due to the conduction band of Mg 2p shifts to the high energy direction. The comparison of Mulliken population and electronic density difference of brucite crystal at 0 GPa and 10.9 GPa shows that the O—H bond is a strong covalent bond and the bond length remains unchanged with the increase in hydrostatic pressure. When the hydrostatic pressure increasing to 10.9 GPa, the H disorder decreases with the H…O′ bond rearrangement, which is consistent with the previous experimental results.
Analysis of the components and biological organic characteristics of Tridacna spp. shells from South China Sea
MEI Yanjun, SHAO Da, LIU Wenqi, YANG Wenqing, YANG Zhongkang, XIE Zhouqing, SUN Liguang
2018, 48(7): 550-559. doi: 10.3969/j.issn.0253-2778.2018.07.005
The largest bivalve shell in the world, the marine bivalve, Tridacna spp., has hard and dense aragonite shells with annual or daily growth lines in its inner shell layers, and is becoming an ideal material for high-resolution paleoclimate reconstructions. However, identification of shell calcilization is necessary before using Tridacnidae as paleoclimate recorders.Five Tridacnidae specimens were collected from the South China Sea. The analysis results of X-ray diffraction (XRD), differential scanning calorimetry - thermo gravimetric analysis (DSC-TGA) and gas chromatography-mass spectrometer (GC-MS) showed that all the Tridacna spp.’s inner shells studied here are entirely made of aragonite, and shell calcilization does not occur. The main inorganic compound of the inner shells is CaCO3, with a content between 96.5%~97.2%; the content of the organic matter, such as hexadecane and 17 kinds of amino acids, is between 2.8%~3.5%. However, calcilization takes place in some outer shell layers. This study presents a method to identify the calcilization of Tridacnidae shell, and preliminarily determines composition and content in Tridacnidae shell. Results from this study provide a basis for such reconstruction using Tridacnidae shells.
Spatial distribution and environmental assessment of heavy metals in the soil of the Huaibei mining area
SUN Hao, ZHOU Chuncai, XU Zhongyu, WANG Xingming, LIU Guijian
2018, 48(7): 560-566. doi: 10.3969/j.issn.0253-2778.2018.07.006
To investigate the spatial distribution of heavy metals and environmentally evaluate heavy metals in soil, 311 soil samples were taken from the Huaibei mining area, and the content of Cr, Ni, Cu, Zn, Pb, and As in these samples were measured. Results show that the six heavy metals are enriched to a certain extent in soil, with Zn being the most enriched metal element. Enrichment of Cu, Zn, and Pb is the result of human activities such as coal mining, use of chemical fertilizers, and transportation. A joint effect of natural and human activities enriched Cr and Ni. Natural factors, such as the soil parent material, play a role in the spatial distribution of As. Environment evaluation results show that the Huaibei mining area is in general slightly polluted or not polluted by heavy metals and faces only minor environmental risk.
Seasonal variations in haze and its dominant meteorological factors in Anhui Province
CHEN Fengjiao, WANG Tijian, QIU Kangjun, WEN Huayang, LIU Huilan, LU Mingming, SHI Chun’e, Yang Yuanjian
2018, 48(7): 567-579. doi: 10.3969/j.issn.0253-2778.2018.07.007
Based on the ground-based observations from 63 national stations from 1980 to 2010 in Anhui province, the seasonal variations in haze and its closely related meteorological factors (i.e., relative humidity and wind speed) were analyzed . Results show that: ① before 1995, the largest frequency for haze appeared in winter, followed by spring, autumn and summer; after that, the seasonal variations in haze frequency became less obvious. ②During the recent 30-year period, the haze frequencies in summer and autumn increased significantly, especially after 1995, while slight increases were observed both in spring and winter. ③When haze occurred, the wind directions in four seasons all exhibited features of high frequencies of northeasterly wind and calm wind, and low frequency of Southerly wind. The wind speed in summer and autumn decreased noticeably under haze-weather conditions, and ~48.5% (54.5%) of the haze in summer (autumn) occurred when the wind speed (14h) declined to below 2m/s. ④Haze formations are more closely related to high relative humidity (>70%) conditions in most regions of Anhui province. However, in more polluted regions ( e.g., Hefei and Bengbu), ~ 71.2% and 68.9% of haze events are associated with low relative humidity conditions (<70%). ⑤The frequencies of haze under different relative humidity conditions increased significantly in summer and autumn, with a confidence level of over 95%. The increases in the days of small wind speed (≤2 m/s) are one possible factor for the increases in haze frequencies in summer and autumn.
Relations between circulation patterns and precipitation area of regional persistent torrential rain during flood season in Hunan
PENG Lili, XIE Ao, LUO Bailiang, ZHANG Chao, DAI Zejun, LI Yizhi
2018, 48(7): 580-593. doi: 10.3969/j.issn.0253-2778.2018.07.008
Based on daily rainfall data and the NCEP/NCAR reanalysis data from 1961 to 2016, and according to the definition of regional persistent torrential rain (RPTR), features of typical circulation pattern of RPTR during the flood season in Hunan province and their relation to the distribution of first-day precipitation area were statistically analyzed. Results are as follows:①RPTR often occurs in six major circulation patterns, namely, two-trough-one-ridge, two-trough-two-ridge, two-ridge-one-trough, zonal fluctuation, typhoon depression and mutil-vortex;②RPTR occurs mainly in June, July, followed by May and August, and the probability of occurrence in April and September is small. Besides, the spatial distribution of RPTR cumulative frequency varies in different circulation patterns;③Similar characteristics of circulation at 500hPa are found in the middle-high latitude, which are conducive to the southwards moving of northern cold air to Hunan. However, due to the different intensities and morphological configurations of low latitude of the West Pacific subtropical high, the northern extension of southwest monsoon at 850hPa varies accordingly, resulting in significant difference in torrential rainfall area on the first day.
Characteristics of n-decane lifted flame in coflow jets at elevated temperatures
JIANG Nianpeng, YAN Ye, YE Taohong
2018, 48(7): 594-599. doi: 10.3969/j.issn.0253-2778.2018.07.009
Characteristics of n-decane lifted flame in coflow jets at elevated temperatures and different fuel mole fractions were experimentally studied. The results show that n-decane lifted flame has a tribrachial flame structure in the flame base. After the introduction of the buoyance-induced velocity, the liftoff velocity has a good correlation with the stoichiometric laminar burning velocity. The dimensionless liftoff velocity and blowout velocity are reasonably correlated with coflow air temperature. The liftoff height of the fuel flame increases with the increase in the fuel jet velocity, and decreases with the increase in the mole fraction of the fuel at a certain initial coflow air temperature and in air temperature for a certain mole fraction.
Study on experimental device and measurements for interface thermal resistance of adhesive structure of CFRP
WANG Xiangwang, HU Peng, LIU Yang
2018, 48(7): 600-604. doi: 10.3969/j.issn.0253-2778.2018.07.010
The adhesive structure of carbon fiber reinforced plastics (CFRP) is an important part of the high precision solid surface reflector, the thermal load is the main load of the reflector in orbit, and the interface thermal resistance has an important influence on the temperature distribution of high precision solid surface reflector in orbit. According to the principle of interface thermal resistance measurement, an experimental device was designed to accurately measure the thermal conductivity of CFRP monolithic structure and the interface thermal resistance of cementation structure at different temperatures. The accuracy of the experimental device was verified by comparing the measured thermal conductivity of 304 stainless steel with the standard values. To improve the thermal conductivity of epoxy resin, three single additives were introduced: silicon nitride (β-Si3N4), alumina (Al2O3), and graphene. The experimental results show that as the volume fraction of additives increases, the thermal conductivity also increases, thus enhancing the heat transfer at the bonding sites and reducing the interface thermal resistance. Under the same conditions, the interface thermal resistance of the adhesive decreases with the increase of temperature.