无根萍、酵母菌和红螺菌的水质净化和抑藻作用

从2005年9月到2005年10月,利用莲花湖中的3个49m2,深度为1.5m的围隔进行生物水质净化和除藻研究。1#围隔为对照,2#围隔水体中加入无根萍,3#围隔水体中喷洒酵母菌和光合细菌。与1#围隔比较,2#围隔水面的无根萍的数目在300L×5×103 L-1,3#围隔的喷洒复合菌数目酵母菌(300L×4×105L-1)和红螺菌(300 L×8×108 L-1)。本实验结果表明:在30 d内,2#和3#围隔中的TP分别下降40%、25%;TN分别下降43%、16%;叶绿素含量分别下降51%、31%。透明

长江流域的鱼类资源及其保护对策

长江水系的鱼类约有300种,其中鲤科鱼类占半数以上,主要的经济鱼类多数属于鲤科。对不同江段的鱼类资源作了简介,并提出了相应的保护措施。上游江段以维护生物多样性,保护特有种为主,需要建立鱼类自然保护区;中游应保证主要经济鱼类的自然繁殖条件,加强珍稀鱼类的人工繁殖放流工作,同时对湖泊幼鱼资源进行保护;下游应注意保持江水质量,严格遵守工业废水排放标准;河口江段应规定幼鲟保护期,建议每年6月15日至7月31日停止一切损害幼鲟资源的渔捞作业。

How polluted is the Yangtze River? Water quality downstream from the Three Gorges Dam

The concentrations of major anions and cations, nitrogen and phosphorus, dissolved and particulate trace elements, and organic pollutants were determined for the middle and lower reaches of the Yangtze River (Changjiang) from below the Three Gorges Dam (TGD) to the mouth at Shanghai in November 2006. The concentration of dissolved inorganic phosphate (DIP) was constant at a low level of 6-8 mu gP/L, but the concentration of nitrate (NO3-) approximately doubled downstream and was closely correlated with K+. This translated to a daily load of well over 1000 It of dissolved inorganic nitrogen (DIN) at Datong. The average concentrations of dissolved Pb (0.078 +/- 0.023 mu g/L), Cd (0.024 +/- 0.009 mu g/L), Cr(0.57 +/- 0.09 mu g/L), Cu (1.9 +/- 0.7 mu g/L), and Ni (0.50 +/- 0.49 mu g/L) were comparable with those in other major world rivers, while As (3.3 +/- 1.3 mu g/L) and Zn (1.5 +/- 0.6 mu g/L) were higher by factors of 5.5 and 2.5, respectively. The trace element contents of suspended particles of As (31 +/- 28 mu g/g), Pb (83 +/- 34 mu g/g), and Ni (52 +/- 16 mu g/g) were close to maximum concentrations recommended for rivers by the European Community (EC). The average concentrations of Cd (2.6 +/- 1.6 mu g/g), Cr (185 +/- 102 mu g/g), Cu (115 +/- 106 mu g/g), and Zn (500 +/- 300 mu g/g) exceeded the EC standards by a factor of two, and Hg (4.4 +/- 4.7 mu g/g) by a factor of 4 to 5. Locally occurring peak concentrations exceed these values up to fourfold, among them the notorious elements As, Hg, and Tl. All dissolved and particulate trace element concentrations were higher than estimates made twenty years ago [Zhang, J., Geochemistry of trace metals from Chinese river/estuary systems: an overview. Estuar Coast Shelf Sci 1995; 41: 631-658.]. The enormous loads of anthropogenic pollutants disposed to the river were diluted by the large water discharge of the Yangtze even during the lowest flow resulting in the relatively low concentration levels of trace elements and organic pollutants observed. We estimated loads of e.g. As, Pb and Ni to the East China Sea to be about 4600 kg As d(-1), 3000 kg Pb d(-1), and 2000 kg Ni d(-1). About 6000 t d(-1) of dissolved organic carbon (DOC) was delivered into the sea at the time of our cruise. We tested for 236 organic pollutants, and only the most infamous were found to be barely above detection limits. We estimated that the load of chlorinated compounds, aromatic hydrocarbons, phenols, and PAHs were between 500 and 3500 kg d(-1). We also detected eight herbicides entering the estuary with loads of 5-350 kg d(-1). The pollutant load, even when at low concentrations, are considerable and pose an increasing threat to the health of the East China Sea ecosystem. (c) 2008 Elsevier B.V. All rights reserved.

Comprehensive statistical investigation of SCM-based transmission over 300 m of FDDI-grade multimode fiber

Rigorous statistical analysis is applied for the first time to identify optimal launch conditions and carrier frequencies for SCM transmission over worst-case MMF. The feasibility of multichannel schemes for 10 Gb/s over 300 m is demonstrated. © 2005 Optical Society of America.

Comprehensive statistical investigation of SCM-based transmission over 300 m of FDDI-grade multimode fiber

Rigorous statistical analysis is applied for the first time to identify optimal launch conditions and carrier frequencies for SCM transmission over worst-case MMF. The feasibility of multichannel schemes for 10 Gb/s over 300 m is demonstrated. © 2005 Optical Society of America.

Molecular beam epitaxy growth and photoluminescence study of room temperature 1.31 mu m (InyGa1-yAs/GaAs1-x Sb-x)/ GaAs bilayer quantum wells

Molecular beam epitaxy (MBE) growth of (InyGa1-yAs/GaAs1-xSbx)/GaAs bilayer quantum well (BQW) structures has been investigated. It is evidenced by photo luminescence (PL) that a strong blue shift of the PL peak energy of 47 meV with increasing PL excitation power from 0.63 to 20 mW was observed, indicating type II band alignment of the BQW. The emission wavelength at room temperature from (InyGa1-yAs/GaAs1-xSbx)/GaAs BQW is longer (above 1.2 μ m) than that from InGaAs/GaAs and GaAsSb/GaAs SQW structures (1.1 μ m range), while the emission efficiency from the BQW structures is comparable to that of the SQW. Through optimizing growth conditions, we have obtained room temperature 1.31 μ m wavelength emission from the (InyGa1-yAs/GaAs1-xSbx)/GaAs BQW. Our results have proved experimentally that the GaAs-based bilayer (InyGa1-yAs/GaAs1-xSbx)/GaAs quantum well is a useful structure for the fabrication of near-infrared wavelength optoelectronic devices. © 2005 Elsevier B.V. All rights reserved.

Influence of growth parameters of frequency-radio plasma nitrogen source on extending emission wavelengths from 1.31 mu m to 1.55 mu m GaInNAs/GaAs quantum wells grown by molecular-beam epitaxy

High (42.5%) indium content GaInNAs/GaAs quantum wells with room temperature emission wavelength from 1.3 mu m to 1.5 mu m range were successfully grown by Radio Frequency Plasma Nitrogen source assisted Molecular Beam Epitaxy. The growth parameters of plasma power and N-2 How rate were optimized systematically to improve the material quality. Photoluminescence and transmission electron microscopy measurements showed that the optical and crystal quality of the 1.54 mu m GaInNAs/GaAs QWs was kept as comparable as that in 1.31 mu m.

Magnetism and photoluminescence in manganese-gallium oxide nanowires with monoclinic and spinel structures

Manganese-gallium oxide nanowires were synthesized via in situ Mn doping during nanowire growth using a vapor phase evaporation method. The microstructure and composition of the products were characterized via transmission electron microscopy (TEM), field emission scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The field and temperature dependence of the magnetization reveal the obvious hysteresis loop and large magnitude of Curie-Weiss temperature. The photoluminescence of the manganese-gallium oxide nanowires were studied in a temperature range between 10 and 300 K. A broad green emission band was observed which is attributed to the T-4(1)-(6)A(1) transition in Mn2+ (3d(5)) ions. (c) 2005 Elsevier B.V. All rights reserved.

A 12-bit 300 MHz CMOS DAC for high-speed system applications

This paper describes a 12-bit 300 MHz CMOS DAC for high-speed system applications. The proposed DAC consists of a unit current-cell matrix for 8 MSBs and a binary-weighted array for 4 LSBs. In order to ensure the linearity of DAC, a double Centro symmetric current matrix is designed by using the Q(2) random walk strategy. To minimize the feedthrough and improve the dynamic performance, the drain of the switching transistors is isolated from the output lines by adding two cascoded transistors.

Room temperature operation of photonic-crystal distributed-feedback quantum cascade lasers with single longitudinal and lateral mode performance

We demonstrate room temperature operation of photonic-crystal distributed-feedback quantum cascade lasers emitting at 4.7 mu m. A rectangular photonic crystal lattice perpendicular to the cleaved facet was defined using holographic lithography. The anticrossing of the index- and Bragg-guided dispersions of rectangular lattice forms the band-edge mode with extended mode volume and reduced group velocity. Utilizing this coupling mechanism, single mode operation with a near-diffractive-limited divergence angle of 12 degrees is obtained for 33 mu m wide devices in a temperature range of 85-300 K. The reduced threshold current densities and improved heat dissipation management contribute to the realization of devices' room temperature operation.

宁南山区施肥对马铃薯生长发育、产量及品质的影响

为探讨在宁南山区不同施肥处理下马铃薯生长发育和产量最佳施肥方式,采取随机区组设计进行田间试验,开展对马铃薯产量和品质影响的研究。结果表明,在当地条件下,处理10收获期干物质积累总量平均比对照增加30.97%,各施肥处理收获期的干物质累积量比对照增加7.35%~73.31%。马铃薯生长发育最佳施肥方式是N 300 kg/hm2、P2O5200 kg/hm2、K2O 200 kg/hm2、M 17.5 t/hm2,(氮肥基施和追肥各一半,磷肥和钾肥以及有机肥全部基施),能增加马铃薯产量并能增加淀粉含量,从而提高马铃薯产品品质。在宁南山区马铃薯生产中可以推广应用这种肥料组配方案。

催化消除NO_x复合氧化物催化剂的研究

氮的氧化物(NOx)是大气中的一种重要的污染物，是酸雨的主要来源，目前氮氧化物的无毒处理已经是国际环保研究中最关键的课题之一。本论文选择了两种复合氧化物：一种是钙钛石结构的含Cu的层状复合氧化物；另一种是以水滑石为前体经焙烧后得的复合氧化物为催化剂对它们的物化性质和对催化消除NOx的活性进行了系统的研究，得到了一些有意义的结果。第一部分：钙钛石型结构的含Cu层状复合氧化物钙钛石复合氧化物由于具有独特的物理化学性质，长期以来一直受到固态物理、固体化学和催化领域的科技工作者的重视。尤其近年来对它们在催化消除NOx反应中的活性的研究引起了催化工作者的极大兴趣，这是由于，一方面，钙钛石类复合氧化物对处理NOx的反应活性比较高，有希望取代贵金属催化剂；另一方面，探讨复合氧化物的固态物理、化学性质与处理NOx反应催化性能的关系，有利于揭示处理NOx反应的催化作用本质，为寻找高效实用的催化剂提供理论依据。本论文系统研究了三个系列含Cu钙钛石型复合氧化物的固态物理化学性质和对NO-CO反应的催化性能，并讨论了二者的关系。主要的工作和结论如下：1) 以La_2CuO_4为模型化合物研究了制备方法对它的性质的影响：用四种制备方法：柠檬酸络合爆炸法，聚乙二醇凝胶法，聚丙烯酰胺凝胶法，DTPA络合法合成了La_2CuO_4。比较了四种方法的特点，和制备方法对La_2Cu0_4的结构的影响，并对所得La_2CuO_4在NO-CO反应中的催化活性的影响进行了研究。结果发现聚乙二醇凝胶法和DTPA络合法有利于形成好的晶形，而聚乙二醇凝胶法和聚丙烯酰胺凝胶法对NO-CO反应有较好的活性，这是由于由不同制备方法得到的样品中的缺陷的种类和含量不I司所致。2) La_(1-x)Ba_xCuO_(3-λ)系列中Ba含量对它的性质的影响：用柠檬酸络合法合成了LaBa_2Cu_3O_(7-λ)，LaBaCu_2O_(5-λ)，La_2BaCu_3O_(7-λ) La_4BaCu_5O_(13-λ)及YBa_2Cu_3O_(7-λ)五种钙钛石结构的复合氧化物。XRD分析表明此系列样品均为层状ABO_3结构（分别为二，三，五层）。用XPS和O_2-TPD对样品中的氧种进行了研究，结果显示样品中存在着两种活性氧种：α氧种和β氧种。在O_2-TPD中低温脱附的是α氧种，它可归属于化学吸附氧与样品中的氧空位的浓度有关。β氧种的脱附温度较高，它归属于晶格氧。利用H_2-TPR和化学分析的手段对样品中的金属离子和活性氧的稳定性进行了表征。结果显示大量的氧空位和Cu~(3+)存在于样品中，并且它们的浓度受Ba离子浓度的影响。此系列样品对CO还原NO的活性研究表明：它们的活性远远高于结构类似的Ln_2CuO_4和Ln_2NiO_4等复合氧化物，在低于300 ℃时N0转化率已接近100％．分析结果表明Cu~(3+)和氧空位对活性起很重要的作用。Ba离子的作用是：一方面使含Cu的ABO_3结构稳定；另一方面使样品更容易吸附NO。3) La_4BaCu_5O_(13-λ)中Mn或C0逐步取代Cu对样品性质的影响合成了两系列分别由Mn或Co逐步取代Cu的样品，XRD分析表明它们仍旧是钙钛石结构。通过XPS，O_2-TPD和化学分析方法对样品中的活性氧种进行了表征，结果表明，当Mn逐步取代Cu离子时，晶格氧增加，而吸附氧开始变化较小，当Mn含量大于Cu含量时，吸附氧迅速减少。在Co取代样品的O_(1s)的XPS谱中，氧种变化较Mn取代的小，这表明Co离子对样品中的氧空位含量的影响较Mn离子的小。氧化还原性能的研究表明当Cu离子被Mn或Co离子部分取代后，Cu离子变得更容易被还原，这表明Cu-M(Mn或CO)之间发生了协同作用，使Cu离子更活泼。当Mn或Co部分取代Cu离子之后，样品对CO还原NO反应的催化活性明显提高，当取代含量达到一定程度时（即X ≥ 3），催化活性迅速降低，这表明Cu离子在反应中起着很重要的作用，经过分析我们认为反应机理如下：Cu~(3+)-O~=-Cu~(3+) + CO → Cu~(2+)-□-Cu~(2+)+CO_2 Cu~(2+)-□-Cu~(2+) → Cu~(3+)-□-Cu~(2+) Cu~(3+)-□-Cu~(2+) + NO~-Cu~(3+)-NO-Cu~(2+) 2Cu~(3+)-NO-Cu~(2+) → 2Cu~(3+)-O~=-Cu~(3+) + N_2 式中□是氧空位，Cu~(3+)-□ 是F心。掺杂部分Mn或Co后，催化活性的提高可以归属于Cu-M之间发生的协同作用使Cu离子更活泼，表征结果表明Cu-Co之间的协同作用较Cu-Mn之间的弱（这可能是由于Co，Cu之间化学性质相似），但掺杂Co的样品的活性较掺杂Mn的要高，同时我们在反应中发现，Co含量较高的样品中反应产物中N_2O比掺杂Mn的样品高出许多，因此我们认为Co离子对反应中反应中间产物N_2O的生成比Mn离子要活性。第二部分以水滑石化合物为前体的复合氧化物水滑石类化合物属于一种阴离子粘土，由带正电荷的金属氧化物／氢氧化物和层间阴离子及水分子组成。以水滑石为母体经焙烧制得的氧化物催化剂用于氧化反应的实例尚不多，且大多用于液相催化反应。最近有文献报道含Co，Cu，Ni水滑石经焙烧后对N_2O分解有很好的活性，但还没有关于此类化合物应用于NO还原和分解的文献报道。我们首次将以水滑石为母体经焙烧制得的尖晶石催化剂用于催化消除NO_x的反应中，考察和表征了变更过渡金属离子时Co-M-Al系列和Mg-M-Al系列催化剂在CO还原NO，NO吸附和NO分解反应中的活性。1) 以Mg-M-Al水滑石为前体的催化剂用共沉淀法合成了一系列Mg-M-Al水滑石（M = Cr，Fe，Mn，Co，Ni，Cu；Mg/M/A1 = 3/1/1）。XRD表征表明所有化合物均为典型的水滑石化合物。通过TG-DTA考察了焙烧对样品的结构和组成的影响。450 ℃焙烧后所有样品的XRD图中仅能发现MgO相，表明过渡金属氧化物均匀地分散在MgO-Al_2O_3中，换句话说，所得样品焙烧后是过渡金属氧化物负载在MgO-Al_2O_3载体上。H_2-TPR研究进一步证实过渡金属氧化物在载体上得到了稳定。此系列样品对C0还原N0反应活性的测定表明Mg-Al-Cu样品表现出远远高于其它样品的活性，而Mg-Al和Mg-Ni-Al在550 ℃以下对反应几乎没有活性，其它样品表现出一定的活性。2) 以Co-M-Al水滑石为前体的催化剂体系经共沉淀法合成了Co-M-Al水滑石（M = 过渡金属），经焙烧后发现样品中有尖晶石相出现。比表面研究表明，在500-700 ℃之间比表面变化较小大约在80m~2/g左右，在更高温度焙烧后比表面迅速下降。此系列样品对NO的吸附性能研究表明Co-Al，C0-Ni-Al，Co-Cr-Al，Co-Fe-Al表现出较高的吸附性能，尤其是Co-Ni-Al在100 ℃对NO表现出100％的吸附；其它样品对NO的吸附较低。用过渡金属离子中d轨道电子在吸附前后的晶体场稳定化能的变化可以很好地解释此系列样品对NO的吸附性能。对NO分解的活性测定表明Co-Ni-A1，Co-Cr-A1和Co-Al表现出了较好的活性，其中Co-Ni-Al的活性最高。其它样品在600 ℃以下几乎没有活性。分析结果表明样品对NO分解有活性的催化剂必须具备两个条件：1：对NO有较好的吸附性能；2: NO分解后产生的氧可以容易的脱附。除Co-Al外，所有样品对CO还原NO表现出很高的活性：在150 ℃即有较高的NO转化率，在180 ℃NO转化率即可达到100％。催化剂的氧化还原性能在反应中起着很重要的作用，H_2-TPR研究发现掺杂其它过渡金属后Co离子的还原温度明显降低，表明Co离子得到了活化。3) 以Co-Cu-Al水滑石为前体的样品用共沉淀法合成了一系列Co/Cu/Al含量不同的水滑石化合物，包括Co/Cu/Al分别为7/1/1，3/1/1及1/1/1和仅含Co或Cu的Co/Al = 3/1，Cu/Al = 3/1等一系列样品。XRD结果表明除Cu-Al外其它样品经焙烧后均出现了尖晶石相。Cu-Al样品经焙烧后出现了CuO相表明样品为CuO负载于Al_2O_3上。NO和CO的TPD研究表明三组份样品对NO和CO的吸附明显高于二组份样品，而且含CO量高的样品对NO和CO的吸附能力更好，表明Co起较强的作用。在三组份样品的NO-TPD脱出物中发现有N_2O和N_2，表明NO在样品表面的吸附为活化吸附。对CO还原NO反应活性的研究表明，三组份样品的活性远远高于二组份样品，且含Co量高的样品活性较高，表明在此系列样品中Co离子起决定性作用，而Cu离子起助催化作用。通过对反应中各组份含量的变化分析，我们认为反应机理如下：CO + O-Cat → CO_2 + □-Cat NO + □-Cat → NO-Cat 2(NO-Cat) → N_2O + O-Cat + □-Cat N_2O + □-Cat → N_2O-Cat N_2_O-Cat → N_2 + O-Cat 2(N_2O-Cat) → N_2 + 2(O-Cat) O-Cat是样品中的晶格氧，在Co-Al中加入其它过渡金属离子使样品中的晶格氧得到活化，因此，催化活性得到提高。用以水滑石为前体，共沉淀法和固相反应法等三种制备方法合成了一系列Co-Cu-Al催化剂，发现以水滑石为前体的样品不论是对NO，CO的吸附性能还是对NO-CO反应的催化活性都远远高于其它方法制备的样品，这可能是由于水滑石可以起到一个模版作用，使Cu, Co离子分散的更均匀，以及使催化剂表面的含氧基团丰富。

The effects of carbonized buffer layer on the growth of SiC on Si

Carbonized buffer layers were formed with C2H4 on Si(100) and Si(111) substrates using different methods and SIC epilayers were grown on each buffer layer at 1050 degrees C with simultaneous supply of C2H4 and Si2H6. The structure of carbonized and epitaxy layers was analyzed with in situ RHEED. The buffer layers formed at 800 degrees C were polycrystalline on both Si(100) and Si(111) substrates whereas they were single crystals, with twins on Si(100) and without tu ins on Si(111)substrates. when formed with a gradual rise in substrate temperature from 300 degrees C to growth temperature. Raising the substrate temperature slowly results in the formation of more twins. Epilayers grown on carbonized polycrystalline lavers are polycrystalline. Single crystal epilayers without twins grow on single crystalline buffer layers without twins or with a few twins. (C) 1999 Elsevier Science B.V. All rights reserved.

古油松年轮记录的沈阳地区300年来的气候变化

本研究通过对沈阳清•昭陵、清•福陵和千山风景区树木年轮气候学考察和取样，共采集了103株古油松样本的树芯和轮盘。依据树木年轮气候学研究的规范做法建立了3地区的STD, RES, ARS三种类型的树轮宽度年表9个。并分析了不同采样点树木年轮所反映的气候信息，在此基础上重建了该区域近300年来的气候变化，开展了区域以及全球气候变化对比研究，以探讨沈阳地区近300年来气候变化的特点、规律和机制： （1）古油松年表与冬季和初春低温的关系较明显，1月的低温最显著，3种年表与冬季、春季和秋季的降水量的相关性均较显著。水汽压、相对湿度在入冬前、生长后期和易发生春旱的5-6月份对年轮宽度的影响表现突出。蒸发是上年全年、当年全年和当年绝大部分月份对油松生长起负效应的因素，其中5月最明显，但1、2月的蒸发量与油松当年的年轮宽度表现出正相关。油松年表的窄轮和窄化突变佐证了1650年以来的35次主要的旱灾年历史记录和59次干旱记录。 （2）本研究成功地检验了沈阳地区古油松年轮宽度年表对太阳活动，地磁活动，太平洋十年震荡和全球气温变化的响应。年轮宽度与这些影响因子均存在共同的周期变化和显著的线性关系。其中，年轮宽度对过去太阳活动和地磁的活动呈明显负相关关系，而且是多种抑、促效应的复合。所有结果表明沈阳城市古油松适于监测极度的诸如El Niño (La Niña)事件的全球环境变化和区域环境异常。 （3）本研究重建了沈阳地区1710-2004年12-1月的极端最低温，并指出其主要低温波动期，高温波动期；重建了沈阳地区1780-2004年1-6月的降水量，并统计了降水量反映的偏湿年份,，偏干年份；同时，分别重建了沈阳地区1780-2004年的年均水汽压、年蒸发量和年均相对湿度，并指出各重建结果所表征的旱涝年份。