植物N;P计量化学：中国高等之外的分异规律与野外试验初步验证

元素化学计量学指从化学计量学的角度出发，通过分析比较生命物质不同结构层次（分子、细胞、器官、机体、种群、群落等）或生态系统中元素的相对比值，来研究各层次相互之间以及生态学过程中元素之间的关系。生态化学计量学研究可以把生态实体的各个层次存元素水平上统一起来，足近年来新兴的一个生态学研究领域，广泛应用于生态学研究中。C，N，P是生物地球化学循环中的重要元素，在生态系统中占有重要地位，许多环境问题都与它们有关，由此这三种元素的化学计量学受到生态学家们的普遍关注。C:N:P化学计量学在水生生态系统中研究较为深入，目前已发展到染色体水平，而在陆地生态系统中的研究较为匮乏近年来由于人类活动的强烈影响，这三种元素的循环在速度和规模上都发生了前所未有的改变，导致一系列环境问题的出现，因此C：N:P化学计量学在陆地生态系统中的研究就显得尤为重要。作为地球生命存在基础的绿色植物，在地球上已有数亿年的演化历史，研究陆地植物的元素化学计量学不仅有助于深入了解植物存在于地球上的内在机制，而且可以为许多环境问题的解决提供理论依据。本文首先建立中国不同地区植物氮磷含量数据库，通过数据分析找出一般规律，并进一步揭示植物不同进化阶段N:P化学计量比的变化规律。在此基础上，通过在内蒙古羊草草原设立不同施肥样地来模拟自然界不同氮磷环境，从试验水平上研究不同施肥处理及施肥梯度下生态系统中氮、磷、有机质的变化规律，并从化学计量学角度研究其内在机制。 利州新建成的中国维管植物数据库（包含1603种植物）研究了不同进化水平以及不同功能群（生活型）间植物N:P比的变化规律，并沿胡焕庸线（胡线）把中团分为为东西两部分，从总体水平上对比了东、西部间叫植物氮磷含量以及N：P的异同。结果表明：l）从演化水平来看，尽管氮磷含量表现出极大的差异，除豆科植物外，植物N：P基本保持稳定水平;2）木本植物与草本植物的N：P比差异．显著，木本植物之间（常绿乔木，常绿灌木，落叶乔木，落叶灌木）N：P不具有显著差异;3）中国东西部植物养分含量和N：P比表现出极显著差异，东部的养分含量低于西部，而N:P显著高于西部。 在内蒙古羊草草原两块永久实验样地（样地A：1980年围封样地和样地B：1999年田封样地）进行了为期两年的N素和P素添加试验。氮素添加梯度为0，5，15，30，50，80 g NHN03.m.2.yr-1。P素添加梯度为0，2，4，8，16，and 32 g P2Osm-2 yr-1（仪分析了羊草器官的结果）。分别从植物器官、物种、功能群水平研究了N素添加对N:P化学计量学的影响，此外还研究了土壤和凋落物C：N:P化学计量学对N素添加的响应。结合生物量的变化趋势，探讨了元素化学计量学对养分状况的指示作用。 1．羊草器官对施肥的响应结果表明，添加N素可以显著提高羊草器官中的含N量，p素可以显著提高器官中的含P量：除2001年样地A中的根茎外，根茎中的含P量基本不受N素添加的影响;茎中的含P量同样表现出不受N素添加影响的趋势（2000年B区茎除外）：N素添加可以显著增大羊草叶片中的含P量(B区2000年叶片除外)。P素添加对羊草器官的含N量没有影响;羊草器官中的氮磷含量施肥处理下表现出显著的正相关关系（N素添加下B区叶片除外）。N素添加对羊草器官的N:P比没有显著影响（A区茎2000年和B区叶片2000年除外）：P素添加显著降低了羊草器官中的N:P比。 2．四种优势植物（羊草、羽茅、针茅和苔草）地上生物量和N:P化学计量学对氮肥的响应研究发现，四个物种的氮磷含量均具有极显著相关关系;氮肥可以显著提高样地A中的羽茅生物量，降低苔草的生物量，而使样地B中的羊草生物量增大;两块样地中，四个物种的氮磷含量及N：P比均随N素水平的增高而增大（样地A中的羽茅N:P比除外）。 3．基于生活型划分的功能群（多年生根茎禾草，多年生丛生禾草，豆科植物，多年生杂类草，一二年生植物，灌木和半灌木）对N素添加的响应研究表明：施N可以提高样地A中的多年生丛生禾草的生物量，而使样地B中的多年生根苇禾草增加;多年生杂类草的相对多度在两个样地中均随施氨水平的增加而显著 降低：在样地B中，施氮可以显著提高不同功能群的氮磷含量;在样地A中，功能群N、P含量对施肥的响应并没有一致的变化规律，添加N素可以显著提高不同功能群的含N量（豆科植物除外），多年生根茎禾草和多年生杂类草的P含量有显著增大的趋势（P < 0.005），而其它功能群（豆科植物、灌木和小半灌木、多年生杂类草和～二年生杂类草）的P含量基本恒定（P>0.05）;在样地A中，多年生丛生禾草，多年生杂类草，一二年生植物，灌木和半灌木的N：P比随施氨水平的增加而显著增大，多年生根茎禾草和豆科植物的N:P比基本不变;在样地B中，多年生丛生禾草的N:P比随施氨水平的增加而显著增大，多年生根茎禾草、多年生杂类草和…二年生杂类草不受施氨水平的影响。 4．添加N素对根实验结果表明：两块样地中，上层根(0-10 cm)的生物量仅在施N后第一年显著增加，而下层根(10-20 cm)的地下生物量在两年的施N处理下均不受施肥梯度的影响i在样地A中，施肥后第一年对根的N、P含量影响不显著，施肥后第二年可以显著增大上层根的N、P含量;在样地B中，添加N素后第一年可以显著增大根的含P量; 在两个样地中，两年的N肥处理对根的N：P比没有显著影响：在施氨处理中，根的N、P含量及N:P比在施肥第一年的响应要高于第二年。 5．所有处理中，上层土壤(O-lO cm)养分含量（有机碳，全氮，全磷）均高于下层土壤（10-20 cm）;在样地A中，氮素添加对r十壤有机碳没有显著性作用，在施肥第一年可以显著增加上层土壤的N、P含量，而在施肥后第二年对土壤N、P含量没有显著影响;在样地B中，添加N素对两年的土壤养分均没有显著影响：养分添加两个样地土壤中的元素比值（C:N比，C:P比，N:P比）没有显著影响;土壤养分对施N一年后的响应要高于第二年。 6．养分添加对凋落物化学特征及化学计量学特征的影响研究结果表明：凋落物现存量不受施肥的影响;2001年凋落物现存量与2000年和2001年的地上生物量相关关系不显著;添加N素可以显著提高凋落物的N含量，而对有机碳含量和P含量没有显著影响;凋落物C：N比随施肥梯度的增大而显著降低，N:P比显著增高，而C:P比没有明显变化。 以上研究结果表明，不同植物功能群的N:P比存在差异，人类活动强烈影响自然植被中的植物N：P比;但植物的N：P比不受植物进化的影响（豆科植物除外）;由于植物已有数亿年的演化历史，同时N与P在植物的结构和功能上具有密切的联系，在生物地球化学循环中办存在耦合作用。因此植物N：P比值恒定可能是一普适性规律。 N素添加试验表明，在植物根、地上器官、物种和功能群水平上N与P均呈显著正相关关系，反映了植物体内的氮磷含量具有协同作用。共存种对N肥的响应不同，表明物种受不同元素的制约。因此除非把生态系统中所有物种对施肥的响应刻画清楚，笼统的认定生态系统缺乏某种元素是不适当的。 施肥试验表明，两种围封时间样地的主要限制性元素不同。极度退化(样地B)植物生长主要缺N，而在保护较好样地(样地A)，P也逐步成为一种限制因素。反映了随着保护时间的增加，植物生长逐渐由N限制型向N、P共同限制型过渡。添加的养分要么被植物吸收，挥发到大气中，或以凋落物的形式返还到土壤表层。但是对养分的预算有待于进一步研究。土壤中的养分含量对N素添加有…个滞后效应，而植物响应较为迅速。功能群N:P比在施肥实验中不能保持恒定，可能是由于实验时间较短的缘故;化学计量学的研究表明羊草草原分解凋落物的微生物受P素的制约，可能是由于植物体内具有高的P素再转运机制。这一结论有待于进一步的验证。氮肥降低了凋落物的C:N比，因此凋落物的分解速率可能将要发生改变。这需要进一步开展C循环的研究。

In vivo studies on toxin accumulation in liver and ultrastructural changes of hepatocytes of the phytoplanktivorous bighead carp i.p.-injected with extracted microcystins

Phytoplanktivorous bighead carp were injected i.p. with extracted microcystins (mainly MC-RR and -LR) at two doses, 200 and 500 MC-LReq. mu g kg(-1) bw, and the changes in extractable MCs in liver and in the ultrastructure of hepatocytes were studied at 1, 3, 12, 24 and 48 h after injection. Quantitative and qualitative determinations of MCs in the liver were conducted by HPLC and LC-MS, respectively. MC concentration in the liver reached the maxima at 12 It (2.89 mu g MCs g(-1) dry weight at the lower dose) or at 3 h (5.43 mu g MCs g(-1) dry weight at the higher dose) post-injection, followed by sharp declines afterwards, whereas the ultrastructural changes of hepatocytes in both dose groups suggest progressive increases in severity toward the directions of apoptosis and necrosis from I to 24 h, respectively. There were two new findings in fish: widening of intercellular spaces was among the early ultrastructural changes induced by MCs and ultrastructural recovery of hepatocytes was evident at 48 h post-injection in both dose groups. Both the present and previous studies suggest that with in vivo or in vitro exposure to microcystins, hepatocyte damage in fish tends to proceed toward the direction of apoptosis at lower MC concentrations but toward the direction of necrosis at high MC concentrations. The temporal dynamics of MCs in the liver suggest that bighead carp may have a mechanism to degrade or bind MC-LR actively after it enters the blood system. (c) 2005 Elsevier Ltd. All rights reserved.

Long-term toxic impact of 2,3,7,8-tetrachlorodibenzo-p-dioxin on the reproduction, sexual differentiation, and development of different life stages of Gobiocypris rarus and Daphnia magna

The sexual ratio of Gobiocypris rarus exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 17 beta -estradiol from embryo to sexually mature revealed feminization and overdevelopment of connective tissue in male fish gonad in 2-30 pg/L TCDD concentration range. Daphnia magna was not sensitive to the high dose of TCDD (0.1-1000 ng/ml), but the reproduction of D. magna treated with TCDD decreased after the 8th day. 7-Ethoxyresorufin-O-deethylase (EROD) activities in newly fertilized eggs of G. rarus exposed to TCDD dosage groups (1000-100,000 pg/L) were significantly induced and increased with TCDD concentrations at the early life stage, while no difference was found between low TCDD dosage groups (<100 pg/L), but a good relationship between the EROD activity and the TCDD concentration was observed during a long-term developmental stage. There was a pericardial edema formed in a 2-week yolk-sac at the concentration of 1000 pg/L TCDD. But in the exposure group (2 pg/L TCDD for 120 days), the cell nuclei of hepatocytes was far from the center and packed toward the cell membrane; the cristae of most mitochondria in the cell dropped and collapsed; the rough endoplasmic reticulum broke into fragments; and numerous lipid droplets formed in the cell. (C) 2001 Academic Press.

Ultrafast carrier dynamics in undoped and p-doped InAs/GaAs quantum dots characterized by pump-probe reflection measurements

We investigate the dependence of the differential reflection on the structure parameters of quantum dot (QD) heterostructures in pump-probe reflection measurements by both numerical simulations based on the finite-difference time-domain technique and theoretical calculations based on the theory of dielectric films. It is revealed that the value and sign of the differential reflection strongly depend on the thickness of the cap layer and the QD layer. In addition, a comparison between the carrier dynamics in undoped and p-doped InAs/GaAs QDs is carried out by pump-probe reflection measurements. The carrier capture time from the GaAs barrier into the InAs wetting layer and that from the InAs wetting layer into the InAs QDs are extracted by appropriately fitting differential reflection spectra. Moreover, the dependence of the carrier dynamics on the injected carrier density is identified. A detailed analysis of the carrier dynamics in the undoped and p-doped QDs based on the differential reflection spectra is presented, and its difference with that derived from the time-resolved photoluminescence is discussed. (C) 2008 American Institute of Physics.

When Does a Polynomial Over a Finite Field Permute the Elements of the Field?

We present a class of indecomposable polynomials of non prime-power degree over the finite field of two elements which are permutation polynomials on infinitely many finite extensions of the field. The associated geometric monodromy groups are the simple ...

on string languages generated by spiking neural p systems

We continue the study of spiking neural P systems by considering these computing devices as binary string generators: the set of spike trains of halting computations of a given system constitutes the language generated by that system. Although the "direct" generative capacity of spiking neural P systems is rather restricted (some very simple languages cannot be generated in this framework), regular languages are inverse-morphic images of languages of finite spiking neural P systems, and recursively enumerable languages are projections of inverse-morphic images of languages generated by spiking neural P systems.

U-transformation-finite element method in 3-dimensional analysis of orthotropic laminates

For an orthotropic laminate, an equivalent system with doubly cyclic periodicity is introduced. Then a 3-dimensional finite element model for the equivalent system is transformed into the unitary space, where the large finite element matrix equation is decoupled into some small matrix equations. Such a decoupling very efficiently reduces the computational effort. For an orthotropic laminate with four clamped edges, no exact elasticity solution is available, and the deflection values predicted by different methods have a considerable difference each other for a small length-to-thickness ratio. The present predictions are the largest because the present method is a full 3-dimensional finite element analysis without superfluous constraints. Illustrative numerical examples are presented to observe the distributions of stresses through the thickness of the laminates. (C) 2010 Elsevier Ltd. All rights reserved.

Symmetry energy and isovector giant dipole resonance in finite nuclei

We study the relationship between the properties of the isovector giant dipole resonance of finite nuclei and the symmetry energy in the framework of the relativistic mean field theory with six different parameter sets of nonlinear effective Lagrangian. A strong linear correlation of excited energies of the dipole resonance in finite nuclei and symmetry energy at and below the saturation density is found. This linear correlation leads to the symmetry energy at the saturation density at the interval 33.0MeV <= S(po) <= 37.0 MeV. The comparison to the present experimental data in the soft dipole mode of (132) Sn constrains approximately the symmetry energy at p = 0.1 fm(-3) at the interval 21.2MeV similar to 22.5 MeV. It is proposed that a precise measurement of the soft dipole mode in neutron rich nuclei could set up an important constraint on the equation of state for asymmetric nuclear matter.

Critical behavior of multifragmentation in finite nuclei and extraction of critical exponents

Using a phenomenological asymmetric nuclear equation of state, we obtained pressure-density isotherms of the finite nucleus Sn-112 simulated in r-space and in p-space and constructed the nuclear fragments by using the coalescence model. After correlatively analysing the fragments, the signal of critical behavior has been found and critical exponents were also extracted.

Thermoplastic Elastomers Based on Compatibilized Poly(butylene terephthalate) Blends: Effect of Functional Groups and Dynamic Curing

Two sets of graft copolymers were prepared by grafting glycidyl methacrylate (GMA) or ally] (3-isocyanate-4-tolyl) carbamate (TAI) onto ethylene/propylene/diene terpolymer (EPDM) in an internal mixer. These graft copolymers were used as the compatibilizer to prepare the thermoplastic elastomers (TPEs) containing 50 wt%, of poly(butylene terephthalate), PBT, 30 wt% of compatibilizer, and 20 wt% of nitrile-butadiene rubber, NBR. The indirect, two-step mixer process was chosen for dynamic curing.

Biodegradable amphiphilic block copolymers bearing protected hydroxyl groups: Synthesis and characterization

A new biodegradable amphiphilic block copolymer, poly(ethylene glycol)-b-poly(L-factide-co-9-phenyl-2,4,8, 10-tetraoxaspiro[5,5]undecan-3-one) [PEG-b-P(LA-co-PTO)], was successfully prepared by ring-opening polymerization (ROP) Of L-lactide (LA) and functionalized carbonate monomer 9-phenyl-2,4,8,10-tetraozaspiro[5,5]undecan-3-one (PTO) in the presence of monohydroxyl poly(ethylene glycol) as macroinitiator using Sn(Oct)(2) as catalyst. NMR, FT-IR, and GPC studies confirmed the copolymer structure.

Synthesis and characterization of novel biodegradable poly(carbonate ester)s with photolabile protecting groups

Novel biodegradable poly(carbonate ester)s with photolabile protecting groups were synthesized by ring-opening copolymerization Of L-lactide (LA) with 5-methyl-5-(2-nitro-benzoxycarbonyl)-1,3-dioxan-2-one (MNC) with diethyl zinc (Et2Zn) as catalyst. The poly(L-lactide-co-5-methyl-5-carboxyl-1,3-dioxan-2-one) (P(LA-co-MCC)) was obtained by UV irradiation Of poly(L-lactide acid-co-5-methyl-5-(2-nitro-benzoxycarbonyl)-1,3-dioxan-2-one) (P(LA-co-MNC)) to remove the protective 2-nitrobenzyl group.

Novel aliphatic poly(ester-carhonate) with pendant allyl ester groups and its folic acid functionalization

A series of novel poly(ester-carbonate)s bearing pendant allyl ester groups P(LA-co-MAC)s were prepared by ring-opening copolymerization Of L-lactide (LA) and 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) with diethyl zinc (ZnEt2) as initiator. NMR analysis investigated the microstructure of the copolymer. DSC results indicated that the copolymers displayed a single glass-transition temperature (T-g), which was indicative of a random copolymer, and the Tg decreased with increasing carbonate content in the copolymer.

Synthesis and characterisation of novel functional polyolefin containing sulfonic acid groups

The strong polar group, sulfonic acid, has successfully been introduced into ethylene/allylbenzene copolymers without degradation or crosslinking via chlorosulfonation reaction with chlorosulfonic acid as a chlorosulforiating agent in 1, 1,2,2-tetrachloroethane followed by hydrolysis. The degree of sulforiation (DS) can be easily controlled by changing the ratio of chlorosulfonic acid to the pendant phenyls of the copolymer. The microstructure of sulfonated copolymers were unambiguously revealed by H-1 NMR and H-1-H-1 COSY spectral analyses, which indicates that all the sulforiation reactions exclusively took place at the para-position of the aromatic rings.

Synthesis and characterization of titanium complexes bearing two beta-enaminoketonato ligands with electron-withdrawing groups and their behavior in ethylene polymerization

A series of new titanium complexes with two asymmetric bidentate beta-enaminoketonato (N,O) ligands (4b-t), [RN=CCF3)CHC(t-BU)O](2)TiCl2 (4b, R = -C6H4F(o); 4c, R = -C6H4F(m);4d, R = -C6H4F(p); 4e, R = - C6H3F2(2,3); 4f, R = -C6H3F2(2,4); 4g, R = -C6H3F2(2,5); 4h, R = -C6H3F2(2,6); 4i, R = -C6H3F2(3,4); 4j, R = -C6H3F2(3,5); 4k, R = -C6H2F3(2,3,4); 4l, R = -C6H2F3(3,4,5); 4m, R = -C6H4CF3(o); 4n, R =-C6H4CF3(m); 4o, R = -C6H4CF3(p); 4p, R = -C6H4Cl(p); 4q, R = -C6H4I(p); 4r, R = -C6H4NO2(P); 4s, R = -CH2C6H5; 4t, R = -C6H11), have been synthesized and characterized.