Stability and equation of state of post-aragonite BaCO3

At ambient conditions, witherite is the stable form of BaCO₃ and has the aragonite structure with space group Pmcn. Above ~10 GPa, BaCO₃ adopts a post-aragonite structure with space group Pmmn. High-pressure and high-temperature synchrotron X-ray diffraction experiments were used to study the stability and equation of state of post-aragonite BaCO₃, which remained stable to the highest experimental P–T conditions of 150 GPa and 2,000 K. We obtained a bulk modulus K ₀ = 88(2) GPa with $K'$  = 4.8(3) and V ₀ = 128.1(5) ų using a third-order Birch-Murnaghan fit to the 300 K experimental data. We also carried out density functional theory (DFT) calculations of enthalpy (H) of two structures of BaCO₃ relative to the enthalpy of the post-aragonite phase. In agreement with previous studies and the current experiments, the calculations show aragonite to post-aragonite phase transitions at ~8 GPa. We also tested a potential high-pressure post–post-aragonite structure (space group C222 ₁ ) featuring four-fold coordination of oxygen around carbon. In agreement with previous DFT studies, ΔH between the C222 ₁ structure and post-aragonite (Pmmn) decreases with pressure, but the Pmmn structure remains energetically favorable to pressures greater than 200 GPa. We conclude that post–post-aragonite phase transformations of carbonates do not follow systematic trends observed for post-aragonite transitions governed solely by the ionic radii of their metal cations.     

中国东部土壤温度、湿度变化的长期趋势及其与气候背景的联系

利用1971-2000年中国722站逐月的土壤温度资料和1981-1998年178站逐旬的土壤湿度观测资料,分析了中国东部土壤温度、湿度变化的长期趋势及其与气温、降水变化的关系.结果表明:①我国东部土壤温度的变化在年际一年代际时间尺度上存在明显的区域性差异,其中东北地区表现为持续上升型,而西北东部一华北、江淮和西南一华南地区均为先降后升型;②1970-2000年代,土壤温度的变化在东北以及西北东部一华北地区有显著的上升趋势,而在江淮和西南一华南地区,总体而言变化趋势不显著.此外,1980-1990年代,各区域土壤湿度的变化趋势均不显著;③在年际一年代际尺度上,各区域土壤温度和气温的变化具有显著的正相关关系,而土壤湿度与土壤温度的变化普遍呈负相关关系,其中尤以西北东部-华北地区最为显著.而在较长的时间尺度上,土壤湿度与降水的变化仍然存在较好的正相关关系.     

Optimization of culturing condition and medium composition for the production of alginate lyase by a marine <Emphasis Type="Italic">Vibrio</Emphasis> sp. YKW-34

Carbohydrases secreted by marine Vibrio sp. YKW-34 with strong Laminaria cell wall degrading ability were screened, and among them alginate lyase was found to be dominant. The effects of medium composition and culturing condition on the production of alginate lyase by marine Vibrio sp. YKW-34 in flask were investigated in this study. In the culture medium of marine broth, no alginate lyase was produced. The activity of the alginate lyase, after being induced, reached 5 UmL^-1. The best inoculum volume and inoculum age were 10% and 12h, respectively. The optimal temperature for alginate lyase production was 25℃. The fermentation medium was composed of 0.5% of Laminaria powder and 0.2% of KNO3 with an initial acidity of pH 8.0. Alginate could induce alginate lyase production but not as efficiently as Laminaria powder did. The addition of fucoidan, cellulose and glucose had negative effect on the alginate lyase production. Other kinds of nitrogen sources, such as yeast extract, beef extract and peptone, had positive effect on the growth of the microorganism and negative effect on alginate lyase production. In addition, the time course of alginate lyase production under the optimized condition was described. The optimal harvest time was 48 h.     

Preparation and characterization of agar,agarose, and agaropectin from the red alga Ahnfeltia plicata

Agar, agarose, and agaropectin were extracted from the red alga Ahnfeltia plicata, and their properties and structures were characterized. Agar was extracted by a comparatively low alkaline consumption of 1.2%. It exhibited a gel strength of 1 152.50±74.25 g/cm~2 and a sulfate content of 0.55%±0.08%. The yield of agar from A. plicata was 24.53%, which is higher than those of other agarophytes commonly used in China. Three kinds of the method were compared for the purification of agarose, and the physicochemical properties of agarose that was prepared under the optimal condition were identical to those of commercially available agarose. Furthermore, agaropectin was purified from A. plicata and characterized by GC, HPLC,UV-spectrum, and FI-IR to understand its composition and structure. It was the first time to comprehensively study the agar and its fractions from the red alga of A. plicata. This research provided an eco-friendly agar extraction method from A. plicata and revealed its potential application for the production of agar, agarose,and agaropectin.     

Anti-oxidant and anti-inflammatory activities of ultrasonic-assistant extracted polyphenol-rich compounds from Sargassum muticum

Polypehnol is an important, potentially bioactive component of Sargassum muticum. In this study, ultrasonic assisted extraction of polyphenol-rich substances was performed using a 38% ethanol solution at a solid:liquid ratio of 1:30 at 68℃ for 32 min, determined by single-factor and response surface methodology(RSM) optimization. The content of polyphenol was 5.66 mg/g in the crude extract. Further extraction showed that the polyphenol mainly distributed in ethyl acetate(SKEE) and water phases(SKEW).The anti-oxidation test by electron spin resonance(ESR) spectrum showed that the SKEE had the strongest scavenging activity on DPPH(1,1-diphenyl-2-picrylhydrazyl) and alkyl radicals. SKEE was shown noncytotoxic but could inhibit the generation of cellular ROS, showing protective effects in H_2O_2 and AAPHinduced Vero cells and UV-B irradiated HaCaT cells. SKEE also significantly inhibited the release of NO of LPS-induced RAW 264.7 cells. Therefore, the polyphenol-rich extracts in ethanol and ethyl acetate showed excellent anti-oxidant and anti-inflammatory activities, which is beneficial to the development of high-value bio-substances.     

Characterization,expression and function analysis of DAX1 gene of scallop (Chlamys farreri jones and preston 1904) during its gametogenesis

DAX1, a member of nuclear receptor superfamily, has a function in the sex determination and gonadal differentiation of several vertebrate species. However, little information about DAX1 of invertebrates is available. Here we cloned a homolog of scallop (Chlamys farreri Jones and Preston 1904) dax1, Cf-dax1, and determined its expression characteristics at mRNA and protein levels. The cDNA sequence of Cf-dax1 was 2093 bp in length, including 1404 bp open reading frame (ORF) encoding 467 amino acids. Unlike those of vertebrates, no conserved LXXLL-related motif was found in the putative DNA binding region of Cf-DAX1. Fluorescence in situ hybridization showed that Cf-dax1 located on the short arm of a pair of subtelocentric chromosomes. Tissue distribution analysis using semi-quantitative RT-PCR revealed that Cf-dax1 expressed widely in adult scallop tissues, with the highest expression level found in adductor muscle, moderate level in mantle, gill and testis, and low level in kidney, ovary and hepatopancreas. The result of quantitative real-time PCR indicated that the expression of Cf-dax1 was significantly higher (P<0.05) in testis than in ovary at the same stage, showing a sex-dimorphic expression pattern. Furthermore, immunohistochemical detection found that Cf-DAX1 mainly located in spermatogonia and spermatocytes of testis and in oogonia and oocytes of ovary, implying that DAX1 may involve in gametogenesis of bivalves.     

新型装配整体式墙体抗震性能试验研究

文中针对北京市建筑设计研究院有限公司提出的两种新型装配整体式剪力墙结构连接构造设计了两组墙片试验。试验墙片采用预制构件,并预埋连接件。装配时,墙片之间利用预埋件焊接连接,称为干式连接;上下层墙片之间采用现浇方式与楼板连接在一起,这种方法增强了墙体的整体性,可大幅度降低混凝土现场湿作业量。本文设计了两组墙片试验,第1组试验检验墙片竖缝位置干式连接方式的抗震性能;第2组试验体检验型钢边缘约束构件、型钢抗剪键和高强度灌浆料后浇带的连接性能。两组试验各建造两个试验体,第1组两个试验体相同,第2组两个试验体分别采用不同的轴压比。试验结果表明:干式连接方式可以充分传递截面上的剪力,使腹板墙和翼缘墙协调工作;采用型钢的约束边缘构件具有较好的延性,有效地延缓了墙片角部的破坏。     

崩塌落石产生涌浪的流固耦合运动分析

库区崩塌落石以直接打击和涌浪的形式威胁航道安全。三维流体力学与固体力学耦合分析崩塌落石产生的涌浪是目前该领域的研究热点和未来发展方向。以三峡库区巫峡剪刀峰河道为例,利用Flow-3D首次建立了一个k-ε湍流模型和GMO碰撞模型的流固耦合模型,假定的落石体积为1.2×10⁴ m³。流固耦合分析结果显示:运动物体在陆地斜坡上进行弹跳、翻滚、滑动;进入水体后,其运动受水体严重影响,运动物体将一部分能量传递给水体,能量传递率约为6.54%;水体获得了能量,最大涌浪达到10 m,但衰减很快,至河道中心线时浪高2.4 m,至对岸边浪高为0.89 m。根据涌浪高度大小进行了航道预警分区,建议将预警区北航道线南移350 m左右,航道内涌浪风险将大大降低,航道安全度得到提高。     

FEM/DEM法在典型柱状危岩体破坏过程数值分析中的应用

有限元/离散元耦合分析方法（FEM/DEM法）可计算连续介质的小变形,也可在新生裂缝并在裂隙间开展大变形计算。文章以位于重庆市巫山县长江左岸的箭穿洞柱状危岩体为例,分析了箭穿洞危岩体可能的破坏过程。分析表明:柱状危岩体的基座处于应力集中状态,既有拉应力集中区也有压应力集中区,应力集中造成柱状危岩体的基座附近边界岩体易破坏。应力集中新生了裂隙,裂隙的延展导致了危岩体的解体和最终的破坏。FEM/DEM方法预演了柱状危岩体压致拉裂的裂隙网络形成和破碎岩体运动过程。FEM/DEM对帮助分析大小变形混合的斜坡变形十分有利,是未来数值模拟的发展方向之一。     

福州长乐机场雷暴及风切变天气特征

利用福州长乐机场1998—2015年雷暴观测资料、2010—2015年自动站观测资料及美国国家环境预报中心(NCEP)逐日再分析资料,对机场雷暴及其伴随的风切变天气特征进行统计分析。结果表明:长乐机场雷暴天气一年四季均有发生,夏季最为频繁,且持续时间较长;雷暴具有明显的日变化特征,主要出现在午后至傍晚,持续时间一般在2 h内,l h以内居多;长乐机场偏西方向是雷暴生成最多的方位。54%的雷暴发生前3 h至结束后3 h内伴有风切变,且偏西方向的雷暴伴有风切变的概率较大。长乐机场弱风切变出现的次数远高于中等强度风切变,而强风切变出现次数最少,且出现在偏西方向的概率较高。伴有风切变的雷暴天气主要有4种环流类型:南支槽型、华北槽型、副高控制型及热带气旋型。