Experimental study on energy dissipation in a 1 kW arcjet thruster

As a simple and reliable propulsion system, arcjet thrusters have been used in multiple satellite missions. In order to improve the efficiency of arcjet thrusters, energy dissipation study was carried out in a 1 kW arcjet thruster with pure N2, H2-N2 and H2 as the propellant. Using a 698 nm interference filter, thermal radiation was isolated from arc and plume emissions and the internal nozzle temperature was obtained by converting the thermal radiation signals. Results show that the addition of hydrogen leads to higher nozzle temperature, which is the determining factor for the mode of arc root attachment. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures. Output energy distribution analysis shows that losses from frozen flow and exhaust thermal losses are the main parts in limiting the efficiency of arcjet thrusters.

Experimental study on energy dissipation in a 1 kW arcjet thruster

As a simple and reliable propulsion system, arcjet thrusters have been used in multiple satellite missions. In order to improve the efficiency of arcjet thrusters, energy dissipation study was carried out in a 1 kW arcjet thruster with pure N2, H2-N2 and H2 as the propellant. Using a 698 nm interference filter, thermal radiation was isolated from arc and plume emissions and the internal nozzle temperature was obtained by converting the thermal radiation signals. Results show that the addition of hydrogen leads to higher nozzle temperature, which is the determining factor for the mode of arc root attachment. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures. Output energy distribution analysis shows that losses from frozen flow and exhaust thermal losses are the main parts in limiting the efficiency of arcjet thrusters.

小麦胚乳蛋白组分和Glu-B3位点基因核心编码区差异与小麦品质关系的研究

小麦加工品质改良已成为我国小麦育种的主要目标之一。特别是我国加入WTO以后，对小麦产品的质量提出了更高的要求，小麦品质改良的任务将更加艰巨和重要，小麦胚乳蛋白是影响小麦加工品质性状的重要因素。因此，深入了解小麦胚乳蛋白对加工品质性状的影响及其分子基础，为品质改良提供理论依据和科学指导，对加速我国小麦品质育种和优质小麦生产具有重要意义。本研究选用在麦谷蛋白5个基因位点(Glu-A1、Glu-B1、Glu-D1、Glu-B3和Glu-D3)上均含不同等位基因的小麦品种99G45和京771及Pm97034和京771杂交F9代共164个麦谷蛋白纯合系，及228个中国推广普通小麦品种和高代育成品系为试材，研究了麦谷蛋白Glu-1和Glu-3位点基因等位变异对籽粒蛋白、湿面筋含量、Zeleny沉降值和SDS沉降值间的关系；本研究还利用小麦A、B和D基因组中低分子量麦谷蛋白亚基（LMW-GS）基因特异引物，通过PCR方法克隆了1个Glu-A3位点和3个Glu-B3位点LMW-GS基因片段，在此基础上分析了不同等位基因对品质造成差异的分子基础；另外，本研究对中国近年推广的部分品种和育成的高代品系资源的多样性进行了分析。现将主要研究结果简述如下： 1. 对来自三个麦区的148份材料的醇溶蛋白组成进行了分析，结果表明，各麦区醇溶蛋白模式具有较大差异。在ω区,A7、B、E、F、G、J、P、Q、S和U仅存在于西南秋播麦区；A3、M、N、R、W和X仅存在于黄淮特种麦区；K仅存在于北方冬麦区；A6是北方冬麦区出现频率最高的带型模式，而西南秋播麦区中D出现的频率最高。ω-区的E、H和M几种模式是以前国内外未曾报道的。且初步确定，这些模式对品质性状具有正效应。至于γ区,A、B、D、E和F在各区均有出现，其中B和E在各区出现的频率都很高，在26.1-39.6％之间。相反，H 仅出现在黄淮特种麦区，J仅限于西南秋播麦区。对于β-区醇溶蛋白，B型模式在所有区中都相当高，而模式A仅存在于第三区.对于α-区，模式A在Ⅲ区而模式D在Ⅱ区出现的频率很高。1BL.1RS易位系在中国小麦品种中出现频率高达41.2％，在I, II和Ⅲ麦区的出现频率分别为 45.5、43.5和35.2%。各生态区模式的差异可能是品种适应不同生态条件和人为选择的结果，但这有待进一步证明。由于醇溶蛋白位点（Gli-1）与LMW-GS位点（Glu-3）紧密连锁，本结果可为下面确定普通小麦LMW-GS等位基因变异所用。 2. 利用Gli-1与Glu-3的紧密连锁，以228个小麦品种/系为材料，首次对中国小麦品种麦谷蛋白亚基的6个位点进行综合分析，研究小麦籽粒蛋白与品质性状间的关系，结果表明6个高分子量（HMW）和低分子量（LMW）麦谷蛋白位点对蛋白质含量的效应大小为，Glu-D1>Glu-B3>Glu-A1=Glu-B1> Glu-A3=Glu-D3；对GMP含量的效应大小为, Glu-A3>Glu-B3>Glu-D1> Glu-B1>Glu-A1>Glu-D3；对湿面筋含量的效应大小为, Glu-B1>Glu-B3= Glu-D3>Glu-A3>Glu-A1>Glu-D1；对Zeleny沉降值的效应大小为, Glu-A1> Glu-B3>Glu-D3>Glu-D1>Glu-B1>Glu-A3；对SDS沉降值的效应大小为, Glu-B3>Glu-A1=Glu-D1=Glu-A3>Glu-D3>Glu-B1。对蛋白含量而言，各位点的最佳组合方式为1、17+18、5+10、Glu-A3e、Glu-B3g、Glu-D3b；对湿面筋含量而言，各位点的最佳组合方式为1、6+8、5+10、Glu-A3d、Glu-B3c、Glu-D3b；对Zeleny沉降值而言，各位点的最佳组合方式为N、17+18、5+10、Glu-A3d、Glu-B3d、Glu-D3b；对SDS沉降值而言，各位点的最佳组合方式为1、7+8、2.2+12、Glu-A3b、Glu-B3g、Glu-D3b。另外，分析了稀有亚基对5+12与2.2+12与品质性状的关系，认为5+12对品质有负效应，2.2+12对品质有正效应。在品质育种时，应对优异组合或优异亚基加以利用。 3. 首次利用重组自交系（RILs）为材料，研究麦谷蛋白亚基表达量与品质性状的关系，通过对重组自交系中各HMW-GS表达量的分析，认为，就单个亚基的表达量而言，7亚基最高；其次为2亚基、5亚基、12亚基和10亚基；亚基9和1的表达量最小；N亚基不表达。对成对出现的亚基对而言，x型和y型亚基的总表达量2+12>5+10>7+9>17+18。就单个亚基与品质性状的关系而言，仅有10亚基的表达量与蛋白含量的相关性达5%的显著水平，2亚基的表达量与湿面筋含量呈负相关，显著水平也达5%，其余单个亚基对品质性状均无显著影响；就x型/y型亚基的比例来看，2/12和5/10对湿面筋含量都有显著的负效应；对某一位点等位基因控制的亚基表达总量来看，2+12对SDS沉降值有显著负效应。另外，本研究得出：2＋12的亚基对的负效应主要体现在2亚基上，且在同一位点上，x型亚基的表达量大于y型。所以推导稀有亚基组合2+10很可能也是劣质亚基。 4. 以 Glu-A1、Glu-B1、Glu-D1、Glu-B3和Glu-D3作为5个因素对99G45/京771和Pm97034/京771杂交后代的蛋白质含量和SDS沉降值进行多因素方差分析。结果表明，Glu-A1和Glu-D3对蛋白含量的加性效应达5％显著水平；Glu-D1 * Glu-D3对蛋白质含量的互作效应也达5%显著水平；其余位点的加性和互作效应对蛋白质含量的影响均不显著。对SDS 沉降值而言，Glu-D1的加性效应最大,贡献率为4.2 % ,达1 %显著水平,其次是Glu-B1位点,贡献率为3.3% ,达5%显著水平。其余位点对SDS 沉降值的加性和互作效应均未达5%显著水平。总体而言, 各位点对蛋白含量的效应大小为Glu-D3 > Glu-A1 > Glu-D1>Glu-B1>Glu-B3；对SDS沉降值的效应大小为Glu-D1>Glu-B1> Glu-D3>Glu-A1> Glu-B3。Glu-D1和Glu-D3位点上等位基因变异对蛋白含量有显著或极显著影响，含Glu-D1d和Glu-D3 GD、Glu-D3 JD基因的株系分别比含Glu-D1a和Glu-D3 PD基因的株系有较高的蛋白含量；在该遗传背景下，麦谷蛋白各基因位点对蛋白含量的效应大小依次排列为：Glu-A1位点1>N；Glu-B1位点7+9>17+18>14+15；Glu-D1位点5+10>2+12；Glu-B3位点GB>JB>PB；Glu-D3位点GB>JB>PB。对SDS沉降值的效应大小依次排列为：Glu-A1位点1>N；Glu-B1位点7+9=17+18>14+15；Glu-D1位点5+10>2+12；Glu-B3位点GB>JB>PB；Glu-D3位点GB>JB>PB。所以，对蛋白含量和SDS沉降值均较好的组合为1，7+9，5+10，GB，GD。 5. 因为GB和PB对品质的效应有显著差异，选取LMW-GS位点特异扩增引物对京771、99G45和Pm97034的Glu-B3位点进行扩增，结果得到三个不一样的扩增片段（Genebank号为DQ539657－DQ539659），得到的基因片段与Genebank中已报道的同类序列高度同源。通过克隆片段组成的分析，发现对Pm97034的序列较京771和99G45段少一个7氨基酸的重复单元，这可能是它较另外两个片段对面筋强度影响小的主要原因；另外，在99G45的序列中，124位处出现L（亮氨酸）代替P（脯氨酸），158位处出现了T（苏氨酸）代换M(蛋氨酸)，这可能是99G45Glu-B3位点序列对SDS沉降值的效应显著优于Pm97034的原因。 6．通过对RILs各位点同普通小麦品种（系）各位点与品质关系的比较，发现对SDS沉降值的效应，各位点在不同研究材料中是不同的，普通小麦中：Glu-B3>Glu-A1=Glu-D1=Glu-A3>Glu-D3>Glu-B1，RILs中：Glu-D1>Glu-B1> Glu-D3>Glu-A1> Glu-B3。利用重组自交系材料（完全排除了1BL/1RS易位干扰）所得到的结果与Gupta and MacRitchie (1994)所得结论一致。进一步证实了1BL/1RS易位对小麦品质的重要影响。对蛋白含量而言，普通小麦品种（系）中，Glu-D1>Glu-B3>Glu-A1=Glu-B1> Glu-A3=Glu-D3，RILs中，Glu-D3 > Glu-A1 > Glu-D1>Glu-B1>Glu-B3，和对SDS沉降值的效应一样，推断在非1BL/1RS易位的情况下，各位点对其效应应为Glu-D3 > Glu-A1 > Glu-D1>Glu-B1>Glu-B3。 对同一位点的等位基因而言，普通小麦和重组自交系中Glu-A1和Glu-D1上的等位基因对品质性状的贡献是一致的，但Glu-B1上的等位基因对SDS沉降值的贡献发生了变化，普通小麦中17+18>7+9，RILs中7+9>17+18，这可能也是1BL/1RS造成的。 Baking quality improved is one of the main object of wheat bread in China. The overall objective of the present studies was to increase the understanding about protein quality in wheat, i.e. to make it possible to improve the production of wheat with desired quality for different end-uses. With the analysis of gluten protein in RILs, 99G45/Jing 771 and Pm97034/Jing, and 228 wheat cultivars or lines in China, the correlations between glutenin compositions and protein content, glutenin macropolymer(GMP), wet gluten content, Zeleny sedimentation value and SDS sedimentation value contentand breadmaking quality were studied. Also a rapid and efficient detection method of geneticpolymorphism at Glu-B3 loci in wheat was established using polymerase chain reaction(PCR).The results obtained were as follows: 1. Cultivated Chinese wheat germplasm has been a valuable genetic resource in international plant breeding. Patterns of gliadin among cultivated Chinese accessions are unknown, despite the proven value and potential novelty. The objective of this work was to analyse the diversity within improved Chinese wheat germplasm. The electrophoretic banding patterns of gliadin in common wheat cultivars and advanced lines were determined by acid-polyacrylamide gel electrophoresis. For 148 leading commercial cultivars and promising advanced lines used in our study, 48 patterns were identified, 29 corresponding to ω-gliadin, 9 to γ-gliadin, 5 to β-gliadin and 5 to α-gliadin. The most frequent patterns were A6 in ω; B in γ; B in β and A in the region of α. 116 band types appeared in the148 samples: 94 accessions had unique gliadin types, and 22 gliadin types while not unique were found in 54 accessions. The gliadin patterns of Chinese wheat cultivars and lines greatly differed from the patterns of wheat lines from other countries. Three patterns, E, J, H, M, N and O in the ω-zone had not previously been reported. Three wheat zones，the Northern Winter Wheat Region, the Yellow and Huai Valley River valleys Winter Wheat Region and the Southwestern Winter Wheat Region，in China showed different frequencies in their gliadin patterns. This information can be used to monitor genetic diversity with Chinese wheat germplasm. 2. To analyse the relationship between the loci and characteristics quality, we utilized the 228 cultivars/lines. The results showed that : For protein content, Glu-D1 >Glu-B3>Glu-A1=Glu-B1>Glu-A3=Glu-D3. For GMP content, Glu-A3>Glu-B3 >Glu-D1>Glu-B1>Glu-A1>Glu-D3. For wet gluten content, Glu-B1>Glu-B3= Glu-D3>Glu-A3>Glu-A1>Glu-D1. For Zeleny sedimentation value, Glu-A1>Glu-B3> Glu-D3>Glu-D1>Glu-B1>Glu-A3, For SDS sedimentation value, Glu-B3>Glu-A1= Glu-D1= lu-A3>Glu-D3>Glu-B1。For protein content, the best combination of 6 loci is (1,17+18,5+10,Glu-A3e, Glu-B3g,Glu-D3b). For wet gluten content, the best combination of 6 loci is (1,6+8,5+10,Glu-A3d,Glu-B3c,Glu-D3b). For Zeleny sedimentation value, the best combination of 6 loci is (N,17+18,5+10,Glu-A3d, Glu-B3d, Glu-D3b). For SDS sedimentation value, the best combination of 6 loci is(7+8,2.2+12,Glu-A3b, Glu-B3g,Glu-D3b)。Additional, we analysed the relationship between the subunits 5+12 and 2.2+12, think that 5+12 was negative for quality, 2.2+12 is postive for quality. It should be effective utilized. 3. It’s the first time to utilize RILs to study the relationship between subunits expression quantity and characteristics quality. The results showed that: For single subunit, the expression quantity of 7 is the highest. Then the 2, 5, 12 and 10. The expression of subunit 9 and 1 is the lowest. Subunit N is not expressed. For subunits, the expression quantity of x type and y type are 2+12>5+10>7+9>17+18. The significant relation of 5% only showed between the expression quantity of subunit 10 and protein content. The relationship between expression quantity of others and characteristic quality was not significant. For x type/ytype, 2/12 and 5/10 is negative relation insignificant level. For the subunit(s) in a loci, Only 2+12 effect SDS sedimentation value negative in significant level. 4. With RILs 99G45/Jing 771 and Pm97034/Jing 771, we found that: The effective of Glu-A1, Glu-D3 and Glu-D1 * Glu-D3 for protein content is significant at 5% level. The effect of other loci for protein wre not significant. For SDS sedimentation value, the effect of Glu-D1is the highest, which contribution is 4.2 % .Then the Glu-B1, contribution is 3.3%. The effect of other loci for SDS sedimentationvalue were not significant. In total, for protein content: Glu-D3 > Glu-A1 > Glu-D1>Glu-B1>Glu-B3; for SDS sedimentationvalue: Glu-D1>Glu-B1> Glu-D3>Glu-A1>Glu-B3. The effect of alleles in Glu-D1 and Glu-D3 loci are significant at 1% or 5%. In Glu-A1, 1>N; Glu-B1, 7+9>17+18>14+15; Glu-D, 5+10>2+12; Glu-B3, GB>JB>PB; Glu-D3, GB>JB>PB. For SDS sedimentation, Glu-A1, 1>N; Glu-B1, 7+9=17+18>14+15; Glu-D1, 5+10>2+12; Glu-B3, GB>JB>PB; Glu-D3, GB>JB>PB. The best combinations for SDS sedimentation value is 1，7+9，5+10，GB，GD. 5. Because of the difference of GB and PB for SDS sedimentation value, we selected the specific primer for LMW-GS loci to amplified the Glu-B3 of Jing771, 99G45and Pm97034. We got 3 amplify fragment (Gene Bank accession number are DQ539657－DQ539659）. We found that the fragment of Pm97034 were deleted a repetitive 7 amino acid domain, which is perhaps the reason effect the gluten strength. Furthermore, in the position 124 of sequence 99G45, L has been replaced with P. Position 158, T replaced M, which may be the reason why the Glu-B3 locus of 99G45 is prefer to Pm97034 when refer to SDS sedimentation value. 6. Comparing the results of RILs and common wheat, we found that perhaps just the1BL/1RS made the difference of loci in different accession.

小麦高分子量谷蛋白新亚基基因1Dx5’的克隆与分子标记

小麦是世界第一大粮食作物, 而HMW- GS 是直接影响小麦品质的重要因子。我国小麦面粉的烘烤品质普遍较差, 这与我国品种缺少优质的HMW- GS 有关，因此创造与发掘新的优质谷蛋白亚基编码基因，并开展相关生化、农学、分子生物学等方面研究、探讨优质的分子机理，对于培育优质小麦新品种具有重要意义。W958是我们培育的种间远缘杂交（T.durum Desf. ×T.aestivum L）优良品系，该品系在1D染色体上具有父母本没有的新型亚基，由于此亚基在SDS- PAGE电泳中具有和1Dx5亚基一样的电泳迁移率, 因此我们将该亚基命名为1Dx5’亚基。为了进一步从分子水平确证该亚基为新亚基和在育种中利用该亚基，本研究对该亚基的遗传规律、基因分子结构、品质特性和农艺性状等进行了分析。结果表明1Dx5’亚基在品质上与1Dx5亚基一样优质，对于品质的贡献大于1Dx2亚基。1Dx5’亚基具有特异的遗传规律，在分离群体中，此亚基占有极大的比例，该特性十分有利于将其导入高产小麦遗传背景中。此外，本研究扩增出了1Dx5’亚基基因的启动子区域、N－端区域和部分中间重复区域，并比较了1Dx5’和传统的1Dx5、1Dx2亚基在此区域氨基酸序列。结果进一步证明了1Dx5’是一个新的基因。通过蛋白质结构模拟分析，认为1Dx5’亚基的优良特性可能是由于1Dx5’亚基的的中部重复区域能形成分子间较强的氢键，加大了分子间的相互作用，使1Dx5’亚基的面团具有优良的品质，这为1Dx5’亚基的应用提供了理论基础。同时，本研究还设计用于区分1Dx5’和1Dx5等位基因的分子标记，解决了利用SDS-PAGE生化标记难以将二者区分的问题。Wheat is one of the major crops utilized worldwide. Nevertheless, due to the lackof the superior HMW- GS, the wheat quality in China is not satisfying. Therefore,identification and characterization of the superior HMW- GS will lay good foundation to the wheat breeding.W958 is a new bread wheat line developed by interspecific cross (T.durum Desf.×T.aestivum L). It contains a novel HMW- GS. We have designated such subunit as1Dx5’ here for its unique character. To confirm that such subunit is innovative andbeneficial for wheat breeding program on the molecular level, we have investigated itin terms of inheritance, DNA and protein sequence, dough property and agronomictrait associated with it. The result shows that 1Dx5’is as superior as 1Dx5 in terms of dough property.In addition, we have cloned the promoter, N- terminal as well as partial centralrepetitive domain of the allele coding for this subunit. Comparison of the amino acidsequence of 1Dx5’ with that of 1Dx5 and 1Dx2 showed that the superior quality of1Dx5’ subunit may result from the degree of conservation of the repetitive sequencesby which the glutenin polymers interact via inter-chain hydrogen bonds formedbetween the subunit repetitive domains with longer subunits forming more stableinteractions. In addition, we have developed two dominant molecular markers tofacilitate the discrimination of 1Dx5’ and 1Dx5 which could no be achieved by SDS-PAGE.

黄土高原水蚀风蚀交错区治理的重要性与紧迫性

在全国范围划分水蚀、风蚀和冻融侵蚀三大侵蚀类型区基础上 ,提出进一步划分水蚀风蚀交错区的必要性及重要意义。黄土高原的强烈侵蚀中心出现在水蚀风蚀交错区 ,该区为黄河粗泥沙的主要来源区 ,生态环境脆弱 ,自然灾害频繁。该区又为世界级大型煤田蕴藏地 ,将建成我国 2 1世纪的能源重化工基地。强化水蚀风蚀交错区综合治理 ,对治黄及西部地区开发具有重大意义。

Folate-Conjugated Micelles and Their Folate-Receptor-Mediated Endocytosis

A folate-conjugated copolymer PEG-PLA-PLL/folate was synthesized and mixed with pure PEG-PLA-PLL and a fluorescent model drug mFITC to prepare folate-conjugated micelles. The distribution of micelles was studied on cancer-cell-bearing mice via frozen slicing. The results show that mFITC is successfully encapsulated into folate(+) and folate(-)micelles; PEG-PLA-PLL micelles the latter can be internalized by both HeLa and CHO cells without selectivity due to their cationic surface charges, while folate(+)micelles exhibit more preferential endocytosis by HeLa cells than by CHO cells. The folate(-)micelles showed retention in both organs and tumors. The folate(+)micelles are a promising active targeting drug delivery system for FR over-expressing cells and they accumulate in tumor beds.

Study on the origin of inverted phase in drying solution-cast block copolymer films

In a previous study, we reported observation of the novel inverted phase (the minority blocks comprising the continuum phase) in kinetically controlled phase separating solution-cast poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer films [Zhang et al. Macromolecules 2000, 33, 9561-7]. In this study, we adopt the same approach to investigate the formation of inverted phase in a series of solution-cast poly(styrene-b-butadiene) (SB) asymmetric diblock copolymers having nearly equal polystyrene (PS) weight fraction (about 30 wt %) but different molecular weights. The microstructure of the solution-cast block copolymer films resulting from different solvent evaporation rates, R, was inspected, from which the kinetically frozen-in phase structures at qualitatively different block copolymer concentrations and correspondingly different effective interaction parameter, chieff, can be deduced. Our result shows that there is a threshold molecular weight or range of molecular weight below which the unusual inverted phase is accessible by controlling the solvent evaporation rate. In comparing the present result with that of our previous study on the SBS triblock copolymer, we find that the formation of the inverted phase has little bearing on the chain architecture. We performed numerical calculations for the free energy of block copolymer cylinders and found that the normal phase is always preferred irrespective of the interaction parameter and molecular weight, which suggests the formation of the inverted phase to have a kinetic origin.

Study of electron transfer across the liquid/ice-like matrix interface by scanning electrochemical microscopy

In this work, we report the findings of a study on scanning electrochemical microscopy (SECM) to investigate the interfacial electron-transfer (ET) reaction between the 7,7,8,8-tetracyanoquinodimethane radical anion (TCNQ(.-)) in 1,2-dichloroethane and ferricyanide in an ice-like matrix (a mixture of insulting ice and conductive liquid) under low temperatures. Experimental results indicate that the formed liquid/ice-like matrix interface is superficially similar in electrochemical characteristics to a liquid/liquid interface at temperatures above -20 degreesC. Furthermore, imaging data show that the surface of the ice-like matrix is microscopically flat and physically stable and can be applied as either a conductive or an insulting substrate for SECM studies. Perchlorate ion was selected as the common ion in both phases, the concentrations of which controlled the interfacial potential difference. The effect of perchlorate concentration in the DCE phase on interfacial reactions has been studied in detail. The apparent heterogeneous rate constants for TCNQ(.-) oxidation by Fe(CN)(6)(3-) in another phase under different temperatures have been calculated by a best-fit analysis, where the experimental approach curves are compared with the theoretically derived relationships. Reaction rate data obey Butler-Volmer formulation before and after the freezing point, which is similar to most other known cases of ET reactions at liquid/liquid interfaces. However, there is a sharp change observed for heterogeneous rate constants around the freezing point of the aqueous phase, which reflects the phase transition. At temperatures below -20 degreesC, surface-confined voltammograms for the reduction of ferricyanide were obtained, and the ice-like matrix became an insulating one, which indicates that the aqueous phase is really a frozen phase.

Observation of inverted phases in poly(styrene-b-butadiene-b-styrene) triblock copolymer by solvent-induced order-disorder phase transition

We report observation of inverted phases consisting of spheres and/or cylinders of the majority fraction block in a poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer by solvent-induced order-disorder phase transition (ODT). The SBS sample has a molecular weight of 140K Da and a polystyrene (PS) weight fraction of 30%. Tapping mode atomic force microscopy (AFM) and transmission electron microscopy (TEM) were utilized to study the copolymer microstructure of a set of solution-cast SBS films dried with different solvent evaporation rates, R. The control with different R leads to kinetic frozen-in of microstructures corresponding to a different combination parameter chi (eff)Z of the drying films (where chi (eff) is the effective interaction parameter of the polymer solution in the cast film and Z the number of "blobs" of size equal to the correlation length one block copolymer chain contains), for which faster evaporation rates result in microstructures of smaller chi (eff)Z. As R was decreased from rapid evaporations (similar to0.1 mL/h), the microstructure evolved from a totally disordered one sequentially to inverted phases consisting of spheres and then cylinders of polybutadiene (PB) in a PS matrix and finally reached the equilibrium phase, namely cylinders of PS in a PB matrix. We interpret the formation of inverted phases as due to the increased relative importance of entropy as chi (eff)Z is decreased, which may dominate the energy penalty for having a bigger interfacial area between the immiscible blocks in the inverted phases.

K+ sensors based on supported alkanethiol/phospholipid bilayers

A novel kind of K+ sensor with valinomycin-incorporated bilayers supported on a gold electrode consisting of self-assembled alkanethiol monolayers (SAMs) and a lipid monolayer has been fabricated successfully. The lipid monolayer is deposited on the alkylated surface of the first alkanethiol monolayer through three different methods, such as the Langmuir-Blodgett (LB) technique, painted method and painted-frozen method. The response of K + sensors produced by a painted or painted-frozen lipid monolayer on an alkanethiol alkylated gold electrode is larger than that by the LB method, which is due to the difference in fluidity of the three kinds of bilayers. Selectivity coefficients KK+, Na+, KK+, Li+, KK+, Ca2+ and KK+, Mg2+ are 10(-4), 10(-4), 2 x 10(-5) and 3 x 10(-5) respectively, and there is no obvious difference among different fabricating methods. A linear response toward the potassium ion was found in the range from 10(-1) M to 10(-5) M with the detection limit of 10(-6) M. The sensor has a slope of 60 mV per decade. Meanwhile, the longevity of the sensor was improved obviously for at least two months at about -10 degrees C. The higher stability shows the possibility to fabricate a practical biosensor.

Supported phospholipid membranes: Comparison among different deposition methods for a phospholipid monolayer

Supported lipid membranes consisting of self-assembled alkanethiol and lipid monolayers on gold substrates could be produced by three different deposition methods: the Langmuir-Blodgett (L-B) technique, the painted method, and the paint-freeze method, By using cyclic voltammetry, chronoamperometry/chronocoulometry and a.c. impedance measurements, we demonstrated that lipid membranes prepared by these three deposition methods had obvious differences in specific capacitance, resistance and thickness. The specific capacitance of lipid membranes prepared by depositing an L-B monolayer on the alkanethiol alkylated surfaces was 0.53 mu Fcm(-2), 0.44 mu Fcm(-2) by the painted method and 0.68 mu Fcm(-2) by the paint-freeze method. The specific conductivity of lipid membranes prepared by the L-B method was over three times lower than that of the painted lipid membranes, while that of the paint-freeze method was the lowest. The difference among the three types of lipid membranes was ascribed to the influence of the organic solvent in lipid films and the changes in density of the films. The lipid membranes prepared by the usual painted method contained a trace amount of the organic solvent. The organic solvent existing in the hydrocarbon core of the membrane reduced the density of the membrane and increased the thickness of the membrane. The membrane prepared by depositing an L-B monolayer containing no solvent had higher density and the lowest fluidity, and the thickness of the membrane was smaller. The lipid membrane prepared by the paint-freeze method changed its structure sharply at the lower temperature. The organic solvent was frozen out of the membrane while the density of the membrane increased greatly. All these caused the membrane to exist in a ''tilted'' state and the thickness of this membrane was the smallest. The lipid membrane produced by the paint-freeze method was a membrane not containing organic solvent. This method was easier in manipulation and had better reproducibility than that of the usual painting method and the method of forming free-standing lipid film. The solvent-free membrane had a long lifetime and a higher mechanical stability. This model membrane would be useful in many areas of scientific research.

TWO SPECIFIC CAUSES OF CELL MORTALITY IN FREEZE-THAW CYCLE OF YOUNG THALLI OF PORPHYRA YEZOENSIS (BANGIALES, RHODOPHYTA)1

Porphyra yezoensis Ueda is an important marine aquaculture crop with single-layered gametophytic thalli. In this work, the influences of thallus dehydration level, cold-preservation (freezing) time, and thawing temperature on the photosynthetic recovery of young P. yezoensis thalli were investigated employing an imaging pulse-amplitude-modulation (PAM) fluorometer. The results showed that after 40 d of frozen storage when performing thallus thawing under 10 degrees C, the water content of the thalli showed obvious effects on the photosynthetic recovery of the frozen thalli. The thalli with absolute water content (AWC) of 10%-40% manifested obvious superiority compared to the thalli with other AWCs, while the thalli thawed at 20 degrees C showed very high survival rate (93.10%) and no obvious correlation between thallus AWCs and thallus viabilities. These results indicated that inappropriate thallus water content contributed to the cell damage during the freeze-thaw cycle and that proper thawing temperature is very crucial. Therefore, AWC between 10% and 40% is the suitable thallus water content range for frozen storage, and the thawing process should be as short as possible. However, it is also shown that for short-term cold storage the Porphyra thallus water content also showed no obvious effect on the photosynthetic recovery of the thalli, and the survival rate was extremely high (100%). These results indicated that freezing time is also a paramount contributor of the cell damage during the freeze-thaw cycle. Therefore, the frozen nets should be used as soon as time permits.

Cryopreservation of flounder (Paralichthys olivaceus) sperm with a practical methodology

A simple and convenient protocol for the cryopreservation of the flounder (Paralichthys olivaceus) sperm was established for "on the spot" cryopreservation of large quantities of semen. The use of three cryoprotectants, dimethyl sulphoxide (DMSO), glycerol (Gly) and methanol was tested in the method. The percentage of motile sperm present in semen after it had been frozen and thawed in the presence of DMSO, Gly or methanol was 60.5 +/- 3.6, 79.17 +/- 4.5 and 13.25 +/- 4.7%, respectively. The fertilization rates of this sperm were 67.06 +/- 15.1, 76.20 +/- 10.0 and 44.93 +/- 22.6%, while the hatching rates of eggs fertilized with this sperm were 37.40 +/- 8.3, 48.18 +/- 25.7 and 23.35 +/- 10.8%, respectively. It was found that Gly and DMSO were better cryoprotectants than methanol, with Gly giving the best overall results. Under scanning electron microscopy, it could be seen that while the majority of the frozen-thawed sperm remained morphologically normal, some exhibited lost or dilated mitochondria, swollen mid-pieces, broken tails, or damaged cell membrane, which probably caused the decrease in motility and fertility of the frozen-thawed sperm. (C) 2003 Elsevier Science Inc. All rights reserved.

Isolation and purification of phycoerythrin from red alga Garcilaria verrucosa by expanded-bed-adsorption and ion-exchange chromatogaphy

R-phycoerythrin was isolated and purified from Gracilaria verrucosa on an expanded-bed adsorption column combined with ion-exchange chromatography, which can effectively solve the problem of blockage of chromatographic columns due to polysaccharides during isolation and purification of phycobiliproteins. 0.1 M (NH4)(2)SO4 proved best to elute R-phycoerythrin from the expanded-bed column, and desalted 0.1 M (NH4)(2)SO4 eluate was used on an ion-exchange column to purify the R-phycoerythrin. Using this two-stage chromatography, the purity (OD565/OD280) of the R-phycoerythrin from G. verrucosa is increased to 4.4, and the yield of purified R-phycoerythrin can reach 0.141 mg . g(-1) of the frozen alga.

Large-scale isolation and purification of R-phycoerythrin from red alga Palmaria palmata using the expanded bed adsorption method

R-phycoerythrin, a light-harvesting protein in some marine algae, and can be widely used in medicine, was isolated and purified from a red alga, Palmaria palmata (Lannaeus) Kuntze, using the streamline column (expanded bed adsorption) combined with ion-exchange chromatography. Because the crude extract was applied to the column upwardly, the column would not be blocked by polysaccharides usually very abundant in the extract of marine alga, this kind of blockage could hardly lie overcome in ordinary chromatographic column. After applying the crude extract containing 0.5 mol/L (NH4)(2)SO4, (NH4)(2)SO4 solution of different concentrations (0.2 mol/L, 0.1 mol/L and 0.05 mol/L) was used to elute the column downwardly and the eluates were collected and desalted. The desalted eluates were then applied onto all ion-exchange chromatographic column loaded with Q-sepharose for further purification of the R-phycoerythrin. Through these two steps, the purity (OD565/OD280) of the R-phycoerythrin from P. palmata was up to 3.5, more than 3.2, the commonly accepted criterion for purity, and the yield of the purified R-phycoerythrin could reach 0.122 mg/g of frozen P. palmata, much higher than that of phycobiliproteins purified with the previous methods. The result indicated that the cost of R-phycoerythrin will drop down with the method reported in this article.