Pretreatment of corn stover and hybrid poplar by sodium hydroxide and hydrogen peroxide

Sodium hydroxide and its derivatives are used as pulping reagents, wherein the spent NaOH is recovered in salt form and reused. In this study, use of low concentration NaOH (1–5%) in pretreatment of corn stover and hybrid poplar was investigated. It was done with the understanding that NaOH can be recovered. One of the main objectives in this study is to explore the potential of H₂O₂ with NaOH for pretreatment of high lignin substrate such as hybrid poplar. Pretreatment time has not been optimized in this study but held constant at 24 h. Corn stover, after treatment with NaOH under moderate conditions, attains near quantitative glucan digestibility. On the other hand, hybrid poplar requires treatment at higher temperature and NaOH concentration to attain acceptable level of digestibility. Supplementation of hydrogen peroxide in the pretreatment significantly raises delignification and digestibility of hybrid poplar. It was also helpful in retaining the carbohydrates in the treated solids. Retention of hemicellulose after pretreatment provides a significant economic benefit as it eliminates the need for detoxifying hemicellulose sugars. As the residual xylan remaining after pretreatment is an impediment to enzymatic digestion of glucan, supplementation of xylanase has significantly increased the digestibility of glucan as well as xylan of the treated hybrid poplar. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

几种木本植物的N2O释放与某些生理活动的关系

使用带有开放气路的气体交换测定系统,同步测定了几种针、阔叶树种的光合作用、呼吸作用及气孔导度．结果表明,低光下树木针叶或叶片释放Ｎ２Ｏ的速率与光合速率无显著相关．伴随根、茎、叶的呼吸,检测到有Ｎ２Ｏ吸收现象,其通量与温度及呼吸强度呈正相关．气孔导度明显影响Ｎ２Ｏ的通量,表明气孔可能是木本植物释放Ｎ２Ｏ的主要途径．     

棘豆属（豆科）一新组

记载了棘豆属一新组。目前该组包括二个种,它们是：黄穗棘豆和绿黄棘豆。过去,国内的学都将黄毛棘豆与黄穗棘豆等同。而文中作者认为黄毛棘豆是黄穗棘豆的一个变种。另外异色黄毛棘豆被作为变种处理。绿黄棘豆是一个中国新分布种。     

几个生态因子对黄盖鲽的影响

黄盖鲽(Psuedopleuronectes yokohameGünther)是鲽科中的冷温性鱼类,广泛分布在日本、朝鲜及我国的东海、黄海和渤海。地方种群多,洄游范尉小,适应能力强,既是底栖生物食性,又可耐较低的温度,虽非名贵鱼种,却具有一定的经济价值,在开展近海增殖时,不存在越冬和效益外流问题。因此,早在60年代,日本山口县和大分县的学者们,便开始着手该品种的人工孵化和增殖放流试验。80年代初已达年放流2—3cm的稚鱼苗7.0×10~6尾的水平。为了在渤海开展增殖工作,建立综     

外源H2O2对湖北海棠根系线粒体膜透性和细胞核DNA的影响

用0．024％（V／V）H2O2处理湖北海棠（Malus hupehensis Rehd．）实生苗根系,30min后,根系线粒体膜通透,陛明显增大,线粒体膜电位（△ψm）和线粒体内Cyt c／a吸光度比值下降;60min后,根系细胞核DNA发生片段化降解。经荧光染料吖啶橙染色后,可见H2O2处理60min以上的根系压片中出现了清晰致密的黄绿色荧光宽,呈现出细胞程序,陛死亡（PCD）的特征。     

Oxygen supply and the adaptations of animals in groundwater

1. The first part of this review focuses on the oxygen status of natural groundwater systems (mainly porous aquifers) and hyporheic zones of streams. The second part examines the sensitivity of groundwater organisms, especially crustaceans, to low oxygen concentrations (< 3.0 mg L^?1 O₂). 2. Dissolved oxygen (DO) in groundwater is spatially heterogeneous at macro- (km), meso- (m) and micro- (cm) scales. This heterogeneity, an essential feature of the groundwater environment, reflects changes in sediment composition and structure, groundwater flow velocity, organic matter content, and the abundance and activity of micro-organisms. Dissolved oxygen also exhibits strong temporal changes in the hyporheic zone of streams as well as in the recharge area of aquifers, but these fluctuations should be strongly attenuated with increasing distance from the stream and the recharge zone. 3. Dissolved oxygen gradients along flow paths in groundwater systems and hyporheic zones vary over several orders of magnitude (e.g. declines of 9 × 10^?5 to 1.5 ×10^?2 mg L^?1 O₂ m^?1 in confined aquifers and 2 × 10^?2 to 1 mg L^?1 O₂ m^?1 in parafluvial water). Several factors explain this strong variation. Where the water table is close to the surface, oxygen is likely to be consumed rapidly in the first few metres below the water table because of incomplete degradation of soil-generated labile dissolved organic carbon (DOC) in the vadose zone. Where the water table is far from the surface, strong oxygen depletion in the vicinity of the water table does not occur, DO being then gradually consumed as groundwater flows down the hydraulic gradient. In unconfined groundwater systems, oxygen consumption along flow paths may be compensated by down-gradient replenishment of DO, resulting either from the ingress of atmospheric oxygen or water recharge through the vadose zone. In confined groundwater systems, where replenishment of oxygen is impossible, the removal time of DO varies from a few years to more than 10 000 years, depending mainly on the organic carbon content of the sediment. Comparison of the hyporheic zones between systems also revealed strong differences in the removal time and length of underground pathways for DO. This strong variability among systems seems related to differences in contact time of water with sediment. 4. Although groundwater macro-crustaceans are much more resistant to hypoxia than epigean species, they cannot survive severe hypoxia (DO < 0.01 mg L^?1 O₂) for very long (lethal time for 50% of the population ranged from 46.7 to 61.7 h). In severe hypoxia, none of the hypogean crustaceans examined utilized a high-ATP yielding metabolic pathway. High survival times are mainly a result of the combination of three mechanisms: a high storage of fermentable fuels (glycogen and phosphagen), a low metabolic rate in normoxia, and a further reduction in metabolic rate by reducing locomotion and ventilation. It is suggested here that the low metabolic rate of many hypogean species may be an adaptation to low oxygen and not necessarily result from an impoverished food supply. 5. An interesting physiological feature of hypogean crustaceans is their ability to recover from anaerobic stress and, more specifically, rapidly to resynthesize glycogen stores during post-hypoxic recovery. A high storage and rapid restoration of fermentable fuels (without feeding) allows groundwater crustaceans to exploit a moving mosaic of suboxic (< 0.3 mg L?1 O₂), dysoxic (0.3–3.0 mg L^?1 O₂) and oxic (> 3 mg L^?1 O₂) patches. 6. It is concluded that although hypogean animals are probably unsuited for life in extensively or permanently suboxic groundwater, they can be found in small or temporarily suboxic patches. Indeed, their adaptations to hypoxia are clearly suited for life in groundwater characterized by spatially heterogeneous or highly dynamic DO concentrations. Their capacity to survive severe hypoxia for a few days and to recover rapidly would explain partly why ecological field studies often reveal the occurrence of interstitial taxa in groundwater with a wide range of DO.     

科尔沁沙地丘间低地樟子松人工林水分利用来源的稳定同位素解析

20世纪50年代以来,樟子松(Pinus sylvestris var.mongolica在中国北方干旱半干旱地区沙地广泛引种.近年来一些早期引种的樟子松人工林出现了早衰现象.分析生境水分条件变化、判断樟子松采取何种水分利用策略对于认识其早衰现象很有裨益.因此,本研究利用稳定同位素示踪技术,研究了科尔沁沙地东南缘固定沙丘丘间低地30年生樟子松人工林的水分来源及其利用的季节动态,分析了降水和土壤水分变化对樟子松水分利用的影响,阐明了樟子松与伴生植物(黄柳Salix gordeieril)在水分来源方面的异同.结果表明,樟子松及其主要伴生植物黄柳枝条水的稳定18O同位素组成(δ18O)存在明显的季节变化;樟子松的水分来源主要来自20～ 40 cm或更深土层;樟子松和主要伴生植物黄柳之间存在明显的水分竞争,后者比樟子松先行利用最近较强降水(如降水量＞10 mm),从而影响樟子松水源的补给.本研究对于揭示沙地樟子松衰退与水分利用策略的关系具有重要意义.     

自然越冬期间茶树叶片生理生化指标和解剖结构的变化

为探讨自然越冬条件下茶树〔Camellia sinensis(Linn.)O.Ktze.〕叶片的生理生化指标和解剖结构变化,以种植于南京的茶树品种'龙井长叶'('Longjingchangye')的10年生植株为研究对象,对自然越冬期间(2012年11月15日至2013年3月31日)其叶片的叶绿素、可溶性蛋白质、可溶性糖、游离脯氨酸和丙二醛(MDA)含量,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性,以及上表皮、下表皮、栅栏组织和海绵组织厚度及上表皮厚度与海绵组织厚度的比值进行了比较分析.结果表明:自然越冬期间,叶片的叶绿素含量随时间推移呈现先降低后升高的变化趋势,而叶片的可溶性蛋白质、可溶性糖、游离脯氨酸和MDA含量以及SOD、CAT和POD活性则总体上呈现先升高后降低的变化趋势,并且均在2013年1月15日达到其各自的最低值或最高值.与入冬前相比,越冬后叶片的叶绿素和可溶性糖含量显著降低,MDA含量略降低,可溶性蛋白质含量显著升高,游离脯氨酸含量及SOD、CAT和POD活性均略升高.自然越冬期间,叶片的上表皮、下表皮、栅栏组织和海绵组织厚度随时间推移总体上呈现先降低后升高的变化趋势,上表皮和栅栏组织厚度在2013年2月15日达到最低值,而下表皮和海绵组织厚度则在2013年1月30日达到最低值;上表皮厚度与海绵组织厚度的比值呈波动变化趋势.与入冬前相比,入冬后叶片的上表皮、下表皮、栅栏组织和海绵组织厚度均显著降低,而上表皮厚度与海绵组织厚度的比值略降低.研究结果显示:自然越冬条件下,茶树具有一定的耐寒能力,为了减轻低温对其机体的伤害可通过增加可溶性蛋白质、可溶性糖和游离脯氨酸合成及提高相关抗氧化酶活性来调解越冬期间的代谢平衡.     

Exceptionally Enhanced Electrode Activity of (Pr,Ce)O2−δ‐Based Cathodes for Thin‐Film Solid Oxide Fuel Cells

It is shown that an electrochemically‐driven oxide overcoating substantially improves the performance of metal electrodes in high‐temperature electrochemical applications. As a case study, Pt thin films are overcoated with (Pr,Ce)O_2?δ (PCO) by means of a cathodic electrochemical deposition process that produces nanostructured oxide layers with a high specific surface area and uniform metal coverage and then the coated films are examined as an O₂‐electrode for thin‐film‐based solid oxide fuel cells. The combination of excellent conductivity, reactivity, and durability of PCO dramatically improves the oxygen reduction reaction rate while maintaining the nanoscale architecture of PCO layers and thus the performance of the PCO‐coated Pt thin‐film electrodes at high temperatures. As a result, with an oxide coating step lasting only 5 min, the electrode resistance is successfully reduced by more than 1000 times at 500 °C in air. These observations provide a new direction for the design of high‐performance electrodes for high‐temperature electrochemical cells.     

2000年间野生稻和栽培稻(O.sativa.L)分布区逆向分离的过程及动力Ⅰ.古今野生稻和栽培稻(O.sativa.L)的分布与人口分布的关系

２０００ａ间,中国境内野生稻分布区域由２４９５５７５ｋｍ２缩减至１３７１０９４ｋｍ２,减少了４５．０６％;分布纬度北界由３８°３′Ｎ南移至２８°１４′Ｎ,南移９°４９′、１１４０ｋｍ;中国境内栽培稻分布区域由４０８１８６０ｋｍ２增加至９６０００００ｋｍ２,增加了１３５．００％;分布北界由３８°Ｎ北移至５３°２９′Ｎ,北移１５°２９′、１７００ｋｍ。人口分布重心主要在黄河流域和长江流域,对该区域野生稻的生存产生不利影响。而促进栽培稻的发展,必须建立野生稻自然保护区。