Ti~(3+)自掺杂TiO_2纳米管/g-C_3N_4复合材料的制备及可见光催化性能

以低温退火制得的TiO_2纳米管和三聚氰胺为原料,经过一步煅烧制备Ti~(3+)自掺杂TiO_2纳米管/g-C_3N_4复合材料.采用热重分析(TGA)、X-射线衍射(XRD)、透射电子显微镜(TEM)、X-射线光电子能谱(XPS)和紫外-可见漫反射光谱(UV-Vis DRS)对Ti~(3+)自掺杂TiO_2纳米管/g-C_3N_4复合材料的热稳定性、组成、结晶性、形貌、化学价态和光学性能等进行了表征.结果表明,将H_2Ti_3O_7预处理后再与三聚氰胺混合热处理,产物是Ti~(3+)自掺杂TiO_2纳米管/g-C_3N_4复合材料,而未经预处理的H_2Ti_3O_7与三聚氰胺混合后热处理得到的是Ti~(3+)自掺杂TiO_2纳米颗粒/g-C_3N_4复合材料.罗丹明B((RhB)水溶液为模拟废水,以300 W氙灯(λ420 nm)为光源,研究了所得产物的可见光催化降解性能.结果表明,与纯的TiO_2和g-C_3N_4相比,Ti~(3+)自掺杂TiO_2纳米管/g-C_3N_4复合材料具有最佳的光催化降解性能,光催化降解80 min时,对RhB的降解率达98.4%.这得益于Ti~(3+)及TiO_(2-x)纳米管与g-C_3N_4构筑的异质结提高了材料对可见光的响应性能,加快了光生电子的传输和分离,降低了电子和空穴的复合几率.     

太阳光照射土壤中多环芳烃化合物(PAHs)光催化降解动力学

以多环芳烃菲(Phe)、芘(Pyr)和苯并[a]芘(BaP)为目标污染物,研究了土壤pH和腐殖酸对太阳光降解PAHs动力学的影响,以及土壤pH对纳米TiO2和半导体Fe2O3催化太阳光降解PAHs动力学的影响.结果表明,太阳光照射下酸性和碱性土壤中PAHs的降解快于中性,在pH相同的条件下,三种PAHs的降解快慢的顺序为BaP>Pyr>Phe.在PAHs污染土壤中加入腐殖酸后光降解速率加快,5mg·kg-1腐殖酸可有效地促进土壤中PAHs的降解,腐殖酸起到敏化作用.在酸性条件下纳米TiO2和半导体Fe2O3催化降解最快,在碱性和中性条件下相差不大.     

Z型MoO3/g-C3N4复合催化剂用于可见光降解萘普生的机制研究

使用一种简单的搅拌焙烧方法成功制备了MoO_3/g-C_3N_4复合材料,通过SEM、TEM、XRD、FTIR、UV-vis和PL等技术对材料进行形貌结构和光学性能的表征.结果表明,MoO_3与g-C_3N_4成功复合,使g-C_3N_4吸收发生红移,扩大了g-C_3N_4的可见光吸收范围,有效地抑制了光生载流子的复合.以非甾体抗炎药萘普生(NPX)为目标污染物,对MoO_3/g-C_3N_4复合材料的光催化性能进行研究,实验表明光催化剂MoO_3/g-C_3N_4对萘普生的去除率是相同条件下纯g-C_3N_4的1.75倍.MoO_3负载量、pH值、催化剂MoO_3/g-C_3N_4的使用量和NPX的初始浓度等因素的研究表明,3%的MoO_3复合量和酸性条件更有利于NPX降解,加大MoO_3/g-C_3N_4的使用量和减少NPX的初始浓度也能加快NPX的降解速率.通过猝灭实验确定了单线态氧和超氧自由基是反应的主要活性物种,ESR测定单线态氧的存在验证了Z型MoO_3/g-C_3N_4降解NPX的机制.     

ZnFe_2O_4/TiO_2复合材料的制备及其在模拟太阳光下光催化降解吲哚美辛的动力学和机理研究

本文制备了ZnFe_2O_4/TiO_2光催化剂,利用紫外可见吸收光谱(UV-Vis)、电子透射显微镜(TEM)和X射线衍射(XRD)对ZnFe_2O_4/TiO_2的形貌、结构和光谱特征进行表征.同时,研究了不同条件下复合材料对吲哚美辛(IDM)的光催化降解规律.结果表明,二氧化钛与铁酸锌能够很好地粘附在一起,使得吸收波长发生了红移,扩大了吸收光谱的范围.当ZnFe_2O_4和TiO_2的质量比为3%时,在模拟太阳光的条件下该光催化剂对IDM的降解效果最好,降解率达到95%.此外,IDM的光催化降解反应符合准一级动力学规律,在p H=5、催化剂投加量为0.2 g·L-1时,光催化剂的降解速率常数是纯TiO_2时的2.15倍.随着光催化剂投加量的增大,IDM的降解速率随之增加.p H=5时最有利于光催化剂对IDM的降解.经过5次循环实验后,催化剂对IDM的光催化降解率仍在92%以上,展现了该光催化剂的稳定性.猝灭实验揭示了光生空穴(h+)和超氧自由基在ZnFe_2O_4/TiO_2光催化体系中对IDM的降解贡献率最大,其中光生空穴(h+)的贡献率为78.2%.     

TiO_2纳米管的制备和光催化降解有毒有机污染物

采用水热法制备TiO2纳米管,利用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)对TiO2纳米管进行表征.并以有机染料罗丹明B(RhB)和2,4-二氯苯酚(2,4-DCP)进行光催化反应,结果表明,TiO2纳米管催化剂对RhB和2,4-DCP有很好的降解效果.通过紫外-可见光谱(UV-Vis)、红外光谱(FTIR)分析和总有机碳(TOC)测定,发现TiO2纳米管/UV体系能使RhB和2,4-DCP发生有效的降解,反应12h后,RhB和2,4-DCP的矿化率分别达到100%和97.12%.同时,采用辣根过氧化物酶(POD)、N,N-二乙基对苯二胺(DPD)分光光度法和苯甲酸荧光光度法分别测定了降解过程中H202和羟基自由基(·OH)的变化,表明TiO2纳米管光催化机理涉及到·OH历程.     

多孔TiO2空心球降解挥发性有机物的性能

为实现挥发性有机物(volatile organic compounds,VOCs)的高效吸附-矿化,本研究以SiO_2为模板、十二胺为成孔剂制备了不同壁厚的多孔TiO_2空心球,并以相同壁厚的SiO_2@TiO_2实心核壳材料做对比研究空心结构的光学和反应特性.采用透射电镜、氮气等温吸附-脱附、X射线衍射、紫外-可见吸收光谱、表面光电压谱等手段表征材料物化结构,以甲苯为VOCs的代表进行光催化降解实验.结果表明,多孔空心TiO_2的比表面积和吸附性能均优于实心TiO_2.同时,空心腔体显著提高了光吸收率和载流子分离效率.当壁厚为27 nm时空心材料对甲苯的降解速率和矿化效率分别达到了1.14 mg·m~(-3)·min~(-1)和81.3%,是相同壁厚条件下实心材料的2.15倍和2.31倍.     

TiO_2纳米管电极光电催化降解四环素

采用电化学阳极氧化的方法,分别以HF酸水溶液和含NH_4F的丙三醇溶液为电解液,制备出高度有序的TiO_2纳米管电极.扫描电镜结果表明,TiO_2纳米管生长形貌良好,其中有机电解质溶液中制备的TiO_2纳米管管长为3μm,而水溶液中制备的TiO_2纳米管长度仅为300 nm.TiO_2纳米管电极经450℃热处理后,表现出明显的锐钛型结构.两种TiO_2纳米管电极均具有较好的光电催化活性,在偏压为4 V时,光电流分别为1.37 m A·cm~(-2)和0.83 m A·cm-2,其中管长3μm电极在180 min内对50 mg·L~(-1)四环素TOC的去除效果约为93%.该电极具有较高的稳定性,重复使用5次,光电催化过程对四环素废水均具有较高的降解效果.在180 min内,四环素的降解率均保持在92%±1%,可重复使用.     

Zn-TiO2纳米管的光催化活性

采用水热合成-浸渍法制备锌掺杂TiO2纳米管(Zn-TiO2纳米管),透射电镜照片显示Zn-TiO2纳米管为两端开口形貌均一的中空管状结构,管径约6～8 nm,壁厚约1 nm,长度约50～200 nm。研究了Zn-TiO2纳米管对甲基橙的光催化性能,结果表明:掺杂适量锌提高了TiO2纳米管对甲基橙的光催化降解性能,0.4%Zn-TiO2纳米管的光催化性能最佳。同时还探讨了Zn-TiO2纳米管用量和初始pH值等因素对光催化降解甲基橙的影响,结果显示Zn-TiO2纳米管能有效地降解甲基橙。随着光催化反应进行,CODCr去除率和脱色率变化规律不完全相同,可能是由于芳基和烷基降解速率不同所致。     

核-壳结构N(x)-TiO_2@C的制备和表面TiO_2晶相调控及可见光催化降解孔雀石绿研究

以C球为核,钛酸四丁酯和四氯化钛为钛源,不同含量尿素为氮源,通过水热法将不同N掺杂量的TiO_2包裹在C球表面.通过控制焙烧条件,调控包在C球表面的TiO_2的晶型.X射线衍射(XRD)表明,随着焙烧温度的提高,可调控TiO_2的晶型由板钛矿/锐钛矿混晶到锐钛矿/金红石混晶最后得到单一金红石相TiO_2;X射线光电子能谱(XPS)表明,N掺杂进入了TiO_2的晶格内.可见光催化降解孔雀石绿研究表明,制备过程加入1 g尿素,煅烧温度为550℃的样品N(1)-TiO_2@C-550℃,其结构为锐钛矿/金红石混晶型,可见光催化效果最好,2 h催化效率达到75%,相比P25提高了11倍.对其可见光催化降解孔雀石绿过程中活性氧物种的捕获可知,·O-2和·OH参与了反应,其中·OH起在光催化过程中占主要作用.     

β-Mo2C纳米管用于葡萄糖催化氧化及燃料电池的构建

采用水热法合成棒状MoO_3纳米材料作为合成β-Mo_2C纳米管的前驱体,然后通过辅助超声搅拌溶剂热法合成Mo-多巴胺复合物,最后通过程序升温处理得到β-Mo_2C纳米管材料.通过X射线衍射(XRD)、透射电子显微镜(TEM)等技术对材料进行表征,并利用循环伏安法(CV)、方波脉冲伏安法(SWV)、线性扫描伏安法(LSV)等电化学方法研究了该材料对葡萄糖的催化氧化性能.实验结果表明,β-Mo_2C纳米管修饰电极阻抗小,传导电子的速率快,对葡萄糖的氧化具有很好的催化效果.利用β-Mo_2C纳米管构建的葡萄糖/O_2燃料电池的开路电位(OCP)为0.47 V,该燃料电池的最大电流密度3.0 mA·cm~(-2)、功率密度0.70 mW·cm~(-2).     

Observations on the function of the glands of the foot of the pediveliger of Ostrea edulis during settlement

The use during settlement of secretions of the 9 different types of gland in the foot of the pediveliger of Ostrea edulis L. was examined experimentally. During settlement, there is a progressive decrease in the crawling speed of the larva and a strengthening of its bond with the substratum. Both changes are related to (a) a change from ciliary to muscular pedal locomotion; (b) the increasing acidity and viscosity of the mucoid secretions used; (c) the secretion of a byssus thread by the glands of the byssus duet; (d) changes in the form and composition of this byssus. At the termination of settlement, the entire contents of 2 types of gland are discharged. Their secretions give rise to the cement which permanently fixes the larva to the substratum. The 9 types of gland are utilised sequentially in a manner closely related to the 6 phases recognised in settlement behaviour.     

On the behaviour of the residence time at the bottom of the mixed layer

To understand why the findings of Deleersnijder et al. [(2006), Environ Fluid Mech 6: 25–42]—the residence time in the mixed layer in not necessarily zero at the pycnocline—are consistent with those of Delhez and Deleersnijder [(2006), Ocean Dyn 56:139–150]—the residence time in a control domain vanishes at the open boundaries of this control domain—, it is necessary to consider a control domain that includes part of the pycnocline, in which the eddy diffusivity is assumed to be zero. Then, depending on the behaviour of the eddy diffusivity near the bottom of the mixed layer, the residence time may be seen to exhibit a discontinuity at the interface between the mixed layer and the pycnocline. If such a discontinuity exists, the residence time is non-zero in the former and zero in the latter. This is illustrated by analytical solutions obtained under the assumption that the eddy diffusivity is constant in the mixed layer.     

刍议医院资产管理的现状及其对策

医院的固定资产和流动资产是医院赖以生存和发展的基础,是一项非经营性国有资产．目前公立医院固定资产、流动资产管理现状不容乐观,针对这种状况,首先分析问题形成的原因,然后提出管理的措施或建议,从而使资产管理工作规范化、制度化、科学化,使有限的卫生资源发挥出最大的社会效益和经济效益．参3．     

豪猪消化系统的解剖研究

为了了解豪猪的消化生理,为豪猪的人工饲养技术研究提供基础依据,以达到高效饲养豪猪的目的,笔者对豪猪的消化器官进行了系统解剖研究.结果表明:豪猪的胃为单室胃.盲肠很发达,这与其能够消化植物纤维有关.豪猪肝脏很发达,其重量为402 g,是其体重的4.59%,肝脏分叶多而明显.     

Mining of the forest and the time path of the price of timber

The paper analyzes the effect of transportation (site specific) costs and the effect of mining (depletion) of the forest on the time path of the price and of the net price of timber in two forestry models. The models differ in that one has zero costs and the other has positive costs. The analyses yield the standard mining theory results for certain cases. They also yield extentions of these results for cases with growth of the harvested trees and/or regeneration on the harvested land. The paper concludes, as one would expect, that the theory of the mine is useful in analyzing the time path of the price of timber.     

Adjusting the economy to the new energy realities of the second half of the age of oil

Our research indicates that, due to the depletion of conventional, and hence cheap, crude oil supplies (i.e. peak oil), increasing the supply of oil in the future would require exploiting lower quality resources (i.e. expensive), and thus will most likely occur only at high prices. This situation creates a system of feedbacks where economic growth, which requires more oil, would require high oil prices that will undermine that economic growth. We conclude that the economic growth of the past 40 years is unlikely to continue unless there is some remarkable change in how we manage our economy.     

Splitting the tail of the displacement kernel shows the unimportance of kurtosis

Animals disperse in space through different movement behaviors, resulting in different displacement distances. This is often described with a displacement kernel where the long-distance dispersers are within the tail of the kernel. A displacement with a large proportion of long-distance dispersers may have impact on different aspects of spatial ecology such as invasion speed, population persistence, and distribution. It is, however, unclear whether the kurtosis of the kernel plays a major role since a fatter tail also influences the variance of the kernel. We modeled displacement in landscapes with different amounts and configurations of habitats and handled kurtosis and variance separately to study how these affected population distribution and transition time. We conclude that kurtosis is not important for any of these aspects of spatial ecology. The variance of the kernel, on the other hand, was of great importance to both population distribution and transition time. We argue that separating variance and kurtosis can cast new light on the way in which long-distance dispersers are important in ecological processes. Consequences for empirical studies are discussed.     

Stimulation of fat-body production in the polyps of the coralPocillopora damicornis by the presence of mutualistic crabs of the genusTrapezia

A mutualism exists between the xanthid crabs of the genusTrapezia and their host corals,Pocillopora damicornis. It has previously been established that these obligate coral residents benefit the coral hosts by defending them against echinoderm predators and by increasing the survival of polyps located deep between the coral branches. In turn, the corals apparently benefit the crabs by producing lipid-filled structures on which the trapezid crabs feed; these fat bodies may contain some of the lipid which in previous studies of coral metabolism has been termed excess. It was determined by experiments conducted at the Hawaii Institute of Marine Biology that the presence of crabs in colonies ofP. damicornis stimulates the polyps to produce the lipid-filled fat bodies; removal of crabs causes corals to cease producing fat bodies. A structure very similar to the fat bodies ofP. damicornis has been reported inAcropora durvillei. Both of these coral genera ordinarily possess xanthid-crab mutualists. This association between branching corals and crustaceans may have evolved because corals of these genera provide shelter among their branches and because these shallow-water corals are evidently capable of releasing lipid which is excess to the corals' metabolic needs, but which can be utilized by the crabs.     

三峡库区消落带土壤中铅污染调查

报道了三峡库区长江干流及小江支流消落带土壤中重金属铅含量背景值的调查结果。结果表明，目前土壤未被重金属铅污染。