含酚酞侧基聚芳醚砜的辐射交联

研究了含酚酞侧基聚芳醚砜(PES-C)的辐射效应,发现在真空下通过γ射线辐照,PES-C发生交联。而且在高温下PES—C的辐射交联程度比在常温下的高。在25℃下,PES-C的凝胶化剂量为6.6×10~5Gy。而在300℃下,PES-C的凝胶化剂量为6.0×10~4Gy。

尼龙6,6(PA_(6,6)及其共混物结晶性能的研究

尼龙6,6(PA_(6,6))是一种典型的结晶性工程塑料,被广泛应用于纺织、机械制造等行业,但其加工温度范围较窄,耐热性差。聚醚砜(PES)具有较高的玻璃化转变温度,是非晶聚合物,可以诱发某些结晶聚合物结晶。PES与PA_(6,6)共混体系的研究报道较少,本文用熔融法将PES与PA_(6,6)制成共混物,企图改善PA_(6,6)的结晶性,以提高其耐热性,取得了较理想的结果。

改性聚醚砜摩擦性能的研究

用摩擦系数很低的聚四氟乙烯(PTFE)改善聚醚砜(PES)的自润滑性。改性后的PES摩擦磨耗性能提高了数倍,特别是在重负荷及油润滑条件下的摩擦性能优异。在本实验范围内,PES/PTFE也表现出较理想的力学性能和部分相容性。

用~(13)C-NMR法研究酚酞/双酚T型聚芳醚砜的序列结构

利用~(13)C核磁共振法研究了酚酞/双酚T型聚芳醚砜共聚物((PP/Bis-T)PES)的序列结构,分析了将双酚T单元引入酚酞型聚芳醚砜(PES-C)聚合物分子中对其酚酞单元的核磁共振谱的影响,并证实了(PP/BiS-T)PES属于无规共聚物。

Evidence for positive selection in phycoerythrin genes of red algae and cyanobacteria Prochlorococcus and Synechococcus

Because of the shortage of phycoerythrin (PE) gene sequences from rhodophytes, peBA encoding beta- and alpha-subunits of PE from three species of red algae (Ceramium boydenn, Halymenia sinensis, and Plocamium telfariae) were cloned and sequenced. Different selection forces have affected the evolution of PE lineages. 8.9 % of the codons were subject to positive selection within the PE lineages (excluding high-irradiance adapted Prochlorococcus). More than 40 % of the sites may be under positive selection, and nearly 20 % sites are weakly constraint sites in high-irradiance adapted Prochlorococcus. Sites most likely undergoing positive selection were found in the chromophore binding domains, suggesting that these sites have played important roles in environmental adaptation during PE diversification. Moreover, the heterogeneous distribution of positively selected sites along the PE gene was revealed from the comparison of low-irradiance adapted Prochlorococcus and marine Synechococcus, which firmly suggests that evolutionary patterns of PEs in these two lineages are significantly different.

光对裙带菜排卵的干扰及单克隆扩增、育苗条件优化

为了进一步完善裙带菜单倍体克隆（简称单克隆，以下同）育苗技术，实现该技术的产业化，本文对单克隆的快速扩增以及育苗条件进行了优化研究。获得如下结果：一、光对裙带菜排卵的干扰现象：一般附苗后4-5天雌雄配子即已形成。接近成熟的卵囊细胞翘起，长度达到50-55μm，直径为19-20μm，一到两天后即可排卵。精子囊略透明，颜色微绿。在11：13（L：D）的光周期下，排卵一般在黑暗开始后5分钟即已开始，5-15分钟后达到高峰。排卵的过程只有几秒钟。卵排出后停留在卵囊开口处，仍与卵囊牢固相连。虽然排卵过程只有几秒钟，一旦这个过程受到光的干扰，就会诱导卵脱离卵囊。实验证实，5-6μmol m~(-2)s~(-1)的微弱光强（显微镜下镜检的光强）即能引起95%的卵从卵囊脱落。根据我们的观察，一旦卵已排出并与卵囊相连，将不再受光的干扰而脱落。脱落的卵很快死亡分解。将配子已经形成但尚未释放的培养转移至连续光下以后，卵仍能排放，但排出的卵大部分脱落（75%），进一步说明了光对排卵的干扰作用。在育苗实践中，为了方便工作，育苗车间内在天黑后的2-3小时内仍有照明，而在第二天早晨取样观察，就会发现许多空的卵囊。我们的实验证实了这是由于排卵过程受到光的干扰引起的。因此，在育苗实践中，为了提高出苗率，在出苗期间，天黑后2-3小时内育苗车间内应避免照明，以降低光导卵的脱落。二、单克隆快速扩增以及育苗条件的优化：（一）、单克隆快速扩增的优化。实验结果表明：1、单克隆快速生长的适宜光照强度为80-120μmol m~(-2)s~(-1)。单克隆的培养密度宜控制在1-10g/L。接种密度以1g/L为宜。2、单克隆藻体内能贮藏氮，因此在单克隆快速扩增过程中，可采用间歇施肥法补充氮源。实验证明，培养液中氨态氮的适宜浓度为20μmol/L，可维持单克隆6天的生长之用（单克隆培养密度1-10g/L）。3、实验证明，在65天内，“老水”对单克隆的生长没有明显的抑制作用。而且，PES培养基除氮的其它成分也可满足单克隆65天的生长需求。4、单克隆快速生长的适宜温度为22 ℃。另外，单克隆密度与消光值之间存在着线形关系，可以通过测量消光值来计算单克隆的培养密度和鲜重，以代替称量法测鲜重。综上，可提出如下单克隆快速扩增的模式：温度为22 ℃；初始光强控制在80-120 μmol m~(-2)s~(-1)；单克隆的接种密度为1g/L；PES培养基（除去氮的成分）可供单克隆65天的培养之用，在这65天内，每隔六天左右将初始氨态氮补充至20 μmol/L；单克隆的培养密度控制在1-10g/L；单克隆培养密度和鲜重可通过测量消光值计算得到。依以上模式，并及时进行扩养，单克隆的鲜重平均日增长率可达25%，以此增长率计算，10g单克隆经一个月培养后鲜重可达8070克，可培育苗帘2000多个，实现海面养殖1000多亩，达到了生产性育苗的要求。（二）、单克隆育苗条件的优化 根据实验结果，可采取如下的育苗优化措施：1、光对排卵有干扰作用。因此，在出苗期间，在天黑后2-3小时内，育苗车间内应避免照明，以降低光导的卵子脱落。2、1μmol/L磷（PO_4~(3-) -P）和70 μmolm/L氮（NH_4~+-N）有利于加速出苗。3、铁对配子体的发育有明显的促进作用。2.5μmolm/L的Fe（III）能使出苗时间提前1-2天，出苗率增加15%左右。4、单克隆育苗较适宜的温度为17 ℃。依以上条件，4-5天左右即可出苗，比一般出苗时间提前1-2天。出苗率也有所增加，例如在实验室条件下，出苗率由原来的50-60%增至80-90%，增加了30%左右。本项研究进一步完善了裙带菜单克隆育苗技术，将大大有利于该技术的进一步推广。

红藻无性繁殖系的诱导及其发育机制的初步研

以红藻中的角叉菜（Chondrus ocellatus）、龙须菜（Gracilaria lemaneiformis）、真江蓠(Gracilaria asiatica)和海膜（Halymenia sinensis）为材料，观察了红藻幼苗的早期发育，通过组织培养构建无性繁殖系，并初步探讨了红藻无性繁殖系的发育及分化机理，为海藻无性繁殖系的获得提供理论基础和依据。 在室内进行了角叉菜的四分孢子和果孢子的细胞培养，并观察其早期发育过程。结果表明，四分孢子和果孢子的早期发育是相似的，可主要分为三个阶段：早期分裂阶段、盘状体阶段和直立体形成阶段。 切段组织培养表明，红藻无性繁殖系的获得主要通过两种途径：一种为切段组织经过培养可直接形成再生植株；另一种为切段组织经培养脱分化，诱导出愈伤组织或类愈伤组织，愈伤组织或类愈伤组织再分化，形成盘状体，盘状体继续发育即可形成再生植株。 通过切段组织培养，获得了龙须菜和真江蓠再生植株。在PES培养液中，添加6－BA（0.25 mg/L）对龙须菜切段组织再生新枝的诱导有促进作用，诱导率可高达84.4％，高浓度的IAA或6－BA（4 mg/L）对切段组织有损伤作用。实验证明伤口大小对切段组织再生新枝有影响，且伤口太大对再生新枝的形成不利。龙须菜的切段组织培养过程中表现出极性。 通过组织培养，诱导出海膜类愈伤组织—丝状体。添加植物生长调节类物质（IAA 和 6-BA）对海膜丝状体的诱导无促进作用。海膜切片在消毒海水中培养即可获得丝状体。海膜丝状体的外植体来源主要有两个：一是健康的藻体； 另一是盘状体，其丝状体的诱导率分别为80％ 和90％。筛选出了丝状体适宜的生长条件：13－23℃，10－15 μE•m−2• s−1，12h：12h（Light: Dark），其中18℃为最佳生长温度。高的光照强度（50 μE•m−2•s−1）对丝状体产生损伤作用。 红藻无性繁殖系的发育途径，根据其获得途径也有两种情况。经过切段组织培养直接获得的无性繁殖系，是切段切口处已分化的细胞表现其全能性，恢复分裂能力，再生新枝，切段表现出极性。极性的上端产生新枝，下端形成固着器，成为一个完整的植株。经过愈伤组织和类愈伤组织获得的无性繁殖系，是切口处已分化的细胞表现其全能性，经脱分化形成愈伤组织和类愈伤组织，附着在基质上后，再分化形成盘状体，按照孢子的早期发育途径，形成直立体幼苗。 通过SDS-聚丙烯酰胺凝胶电泳分析，对龙须菜正常藻体及无性繁殖系发育过程中蛋白的表达进行检测，检测出表达差异的蛋白质，推测这两个蛋白可能与龙须菜切段组织再生有关，其中30 KD的蛋白仅在再生新枝中表达，150 KD和125 KD的蛋白仅在正常生长的龙须菜和龙须菜切段的极性下端中表达。 根据高等植物中与萌芽、分生组织以及愈伤组织发育相关的基因序列保守区设计了五对特异引物，通过PCR和RT-PCR扩增检测及DNA测序分析，对红藻无性繁殖系早期发育相关的基因序列，进行了初步分析。

Photoelectron spectroscopy of ammonia via a fast predissociative state

We report a study on resonance enhanced multiphoton ionization photoelectron spectroscopy (REMPI-PES) involving the fast predissociative (A) over tilde state of ammonia, using nano- and femtosecond lasers. The multiphoton scheme involves (1 + 1), (2 + 2), (2 + 2) + 1 and (2 + 2) + 2 photon processes. We have found a progression of stretching vibrations nu(1) in the PE spectrum when pumping NH3 (A) over tilde upsilon(2) = 0, 1 and 3 as intermediate states. The stretching vibration intensity distributions in the photoelectron spectrum are calculated by using the Chebychev method of the wavepacket propagation. The femtosecond spectrum shows a similar feature to the nanosecond spectrum. However, high laser power also causes band broadening and shifting effect as well as above threshold multiphoton ionization.

Tecnologia de farinhas mistas.

Conteúdo: - v. 1. Uso de farinha mista de trigo e mandioca na produção de pães - Ahmed El-Dash, Moacir Roberto Mazzari, Rogério Germani (Ed.); v. 2. Uso de farinha mista de trigo e milho na produção de pães - Ahmed El-Dash, Rogério Germani (Ed.); v. 3. Uso de farinha mista de trigo e soja na produção de pães - Ahmed El-Dash, Lair Chaves Cabral, Rogério Germani (Ed.); v. 4. Uso de farinha mista de trigo e sorgo na produção de pães - Ahmed El-Dash, José Emílio Campos, Rogério Germani (Ed.); v. 5. Uso de farinhas mistas na produção de massas alimentícias - Ahmed El-Dash, Rogério Germani (Ed.); v.6. Uso de farinhas mistas na produção de biscoitos - Ahmed El-Dash, Rogério Germani; v. 7. uso de farinhas mistas na produção de bolos - Ahmed El-Dash, Rogério Germani (Ed.).

Replacing rubber plantations by rain forest in Southwest China - Who would gain and how much?

The cultivation of rubber trees in Xishuangbanna Prefecture in China’s Yunnan Province has triggered an unprecedented economic development but it is also associated with severe environmental problems. Rubber plantations are encroaching the indigenous rainforests at a large scale and a high speed in Xishuangbanna. Many rare plant and animal species are endangered by this development, the natural water management is disturbed and even the microclimate in this region has changed over the past years. The present study aims at an assessment of the environmental benefits accruing from a reforestation project partly reversing the deforestation that has taken place over the past years. To this end a Contingent Valuation survey has been conducted in Xishuangbanna to elicit local residents’ willingness to pay for this reforestation program that converts existing rubber plantations back into forest. It is shown that local people's awareness of the environmental problems caused by increasing rubber plantation is quite high and that in spite of the economic advantages of rubber plantation there is a positive willingness among the local population to contribute financially to a reduction of existing rubber plantations for the sake of a partial restoration of the local rainforest. These results could be used for the practical implementation of a PES (Payments for Eco-System Services) system for reforestation in Xishuangbanna.

Charge exchange and dissociative processes in collisions of slow He2+ ions with H2O molecules

Experimental and theoretical studies of one-electron capture in collisions of He2+ ions with H2O molecules have been carried out in the range 0.025-12 keV amu(-1) corresponding to typical solar wind velocities of 70-1523 km s(-1). Translational energy spectroscopy (TES), photon emission spectroscopy (PES), and fragment ion spectroscopy were employed to identify and quantify the collision mechanisms involved. Cross sections for selective single electron capture into n=1, 2, and 3 states of the He+ ion were obtained using TES while PES provided cross sections for capture into the He+(2p) and He+(3p) states. Our model calculations show that He+(n=2) and He+(n=3) formation proceeds via a single-electron process governed by the nucleus-electron interaction. In contrast, the He+(1s) formation mechanism involves an exothermic two-electron process driven by the electron-electron interaction, where the potential energy released by the electron capture is used to remove a second electron thereby resulting in fragmentation of the H2O molecule. This process is found to become increasingly important as the collision energy decreases. The experimental cross sections are found to be in reasonable agreement with cross sections calculated using the Demkov and Landau-Zener models.

Multiple proton translocation in biomolecular systems: concerted to stepwise transition in a simple model

In this paper we study a simple model potential energy surface (PES) useful for describing multiple proton translocation mechanisms. The approach presented is relevant to the study of more complex biomolecular systems like enzymes. In this model, at low temperatures, proton tunnelling favours a concerted proton transport mechanism, while at higher temperatures there is a crossover from concerted to stepwise mechanisms; the crossover temperature depends on the energetic features of the PES. We illustrate these ideas by calculating the crossover temperature using energies taken from ab initio calculations on specific systems. Interestingly, typical crossover temperatures lie around room temperature; thus both concerted and stepwise reaction mechanisms should play an important role in biological systems, and one can be easily turned into another by external means such as modifying the temperature or the pH, thus establishing a general mechanism for modulation of the biomolecular function by external effectors.