Transport properties, structure, and radiation induced defect studies in amorphous carbon films

Amorphous conducting carbon films are prepared by plasma assisted chemical vapour deposition and their d.c. conductivity (similar to 100 Scm(-1)) is studied from 300K down to 4.2K. The films were irradiated by high energy ion beam(I+13, 170 MeV) with a dose of 10(13) ions/cm(2). As a result a marked decrease in conductivity by two to three orders in magnitude was observed. The structural changes and the defects in the films caused by ion irradiation are studied using photoluminescence, persistent photoconductivity, and ESR spectroscopy.

Reactivity of Bispropargyl Sulfones under Basic Conditions: Interplay Between Garratt-Braverman and Schmittel/Myers-Saito Cyclization Pathway

The preference for GarrattBraverman (GB) over MyersSaito (MS) and Schmittel (SCM) cyclizations has recently been demonstrated in sulfones capable of undergoing all three of the processes. As the GB cyclization is a self-quenching process, there is a need to change the selectivity to the non-self-quenching MS or SCM pathway so as to enhance the DNA-cleaving efficiency that operates through the radical-mediated process. Herein we report a conformational constraint-based strategy developed by using computations (M06-2X/6-31+G*) to switch the selectivity from GB to MS/SCM pathway which also results in greater DNA-cleavage activity. The preference for GB could be brought back by easing the constraint with the help of spacers.

Structural Diversity in Multinuclear PdII Assemblies that Show Low- Humidity Proton Conduction

Systematic investigation on synergetic effects of geometry, length, denticity, and asymmetry of donors was performed through the formation of a series of uncommon Pd-II aggregates by employing the donor in a multicomponent self-assembly of a cis-blocked 90 degrees Pd-II acceptor and a tetratopic donor. Some of these assemblies represent the first examples of these types of structures, and their formation is not anticipated by only taking the geometry of the donor and the acceptor building units into account. Analysis of the crystal packing of the X-ray structure revealed several H bonds between the counteranions (NO3-) and water molecules (OHON). Moreover, H-bonded 3D-networks of water are present in the molecular pockets, which show water-adsorption properties with some variation in water affinity. Interestingly, these complexes exhibit proton conductivity (1.87x10(-5)-6.52x10(-4)Scm(-1)) at 296K and low relative humidity (ca. 46%) with activation energies of 0.29-0.46eV. Moreover, the conductivities further increase with the enhancement of humidity. The ability of these assemblies to exhibit proton-conducting properties under low-humidity conditions makes these materials highly appealing as electrolytes in batteries and in fuel-cell applications.

Component Selection in the Self-Assembly of Palladium(II) Nanocages and Cage-to-Cage Transformations

Dynamic supramolecular systems involving a tetratopic palladium(II) acceptor and three different pyridine-and imidazole-based donors have been used for self-selection by a synergistic effect of morphological information and coordination ability of ligands through specific coordination interactions. Three different cages were first synthesized by two-component self-assembly of individual donor and acceptor. When all four components were allowed to interact in a reaction mixture, only one out of three cages was isolated. The preferential binding affinity towards a particular partner was also established by transforming a non-preferred cage into a preferred cage by interaction with the appropriate ligand. Computational studies further supported the fact that coordination interaction of imidazole moiety to Pd-II is enthalpically more preferred compared to pyridine, which drives the selection process. Analysis of crystal packing of both complexes indicated the presence of strong hydrogen bonds between nitrate and water molecules and also H-bonded 3D networks of water. Both complexes exhibit promising proton conductivity (10(-5) to ca. 10(-3) Scm(-1)) at ambient temperature under a relative humidity of circa 98% with low activation energy.

Analysis of dispersion compensation by chirped fiber grating in directly and externally modulated CATV systems

The dispersion compensation effect of the chirped fiber grating (CFG) is analyzed theoretically, and analytic expressions are derived for composite second-order (CSO) distortion in analog modulated sub-carrier multiplexed (AM-SCM) cable television (CATV) systems with externally and directly modulated transmitters. Simulations are given for the two kinds of modulations and for standard single mode fiber and non-zero dispersion shift fiber (NZDSF) systems. The results show that CFG could be used as a dispersion compensator in directly modulated systems, but its dispersion coefficient should be adjusted much more precisely than the externally modulated system. The requirements for the NZDSF system could be loosened much. It is proposed that directly modulated source may be used as a transmitter in CATV systems combined with tunable CFG dispersion compensator being adjusted precisely, which may be more cost-effective than externally modulation technology. (c) 2006 Elsevier GmbH. All rights reserved.

Caracterização do maciço Santa Clara no município de Cujubim (RO) com base em litogeoquímica, geocronologia e estudos isotópicos

A Suíte Intrusiva Santa Clara está inserida na Província Estanífera de Rondônia, na porção SW do Cráton Amazônico. Essa suíte intrusiva é composta pelos maciços Santa Clara, Oriente Velho, Oriente Novo, Manteiga-Sul, Manteiga-Norte, Jararaca, Carmelo, Primavera e das Antas. Os litotipos que perfazem a Suíte Santa Clara ocorrem hospedados nas rochas do Complexo Jamari, uma associação polideformada composta por gnaisses ortoderivados e paraderivados. Características observadas em campo e em análises petrográficas permitiram subdividir o Maciço Santa Clara em cinco fácies distintas: fácies porfirítica, fácies isotrópica, fácies fina, fácies piterlítica e fácies viborgítica. Os litotipos observados correspondem a hornblenda-biotita granitos e biotita granitos intermediários a ácidos, com composições médias semelhantes àquelas verificadas para sienogranitos e monzogranitos. Geoquimicamente, três magmas podem ser identificados. O magma menos evoluído corresponde às rochas das fácies porfirítica e equigranular, e o mais evoluído compreende as fácies de granulometria fina e piterlítica. A fácies viborgítica representa o terceiro líquido magmático, e aparentemente é diferente de todas as outras fácies em termos de aspectos de campo e geoquímica. A análise litogeoquímica indica que estes granitoides são subalcalinos, bastante empobrecidos em MgO e exibem caráter metaluminoso a fracamente peraluminoso. Os padrões de elementos-traços evidenciam que tais granitóides possuem alto conteúdo em elementos incompatíveis (Rb, Zr, Y, Ta, Ce) e ETR, com exceção do Eu. Além disso, também exibem leve enriquecimento em LILE, forte depleção em elementos como Sr e Ti, e leve empobrecimento de Ba, indicando que o fracionamento de minerais como plagioclásio e titanita foi importante na evolução do líquido magmático analisado. A anomalia negativa de Nb indica envolvimento de material crustal nos processos magmáticos que geraram estes granitoides. Os litotipos analisados possuem características típicas de granitos tipo-A ferroan, e as razões FeOt/MgO entre 4,27 e 26,22 sugerem tratar-se de uma série de granitos félsicos fracionados. Os padrões de ETR observados para os litotipos analisados exibem um considerável enriquecimento em ETRL, e anomalia negativa de Eu, sugerindo fracionamento de feldspato durante o processo de diferenciação do líquido magmático. Diagramas discriminantes de ambientes tectônicos sugerem que os litotipos do Maciço Intrusivo Santa Clara são típicos de ambiente intraplaca, do tipo-A2, isto é, associados a ambientes pós-colisionais/pós-orogênicos. As características isotópicas observadas para os granitoides do Maciço Santa Clara sugerem que os mesmos foram gerados a partir da fusão parcial de uma crosta inferior pré-existente. As idades U-Pb entre 1,07 e 1,06 Ga são compatíveis com um magmatismo ocorrido nos estágios finais da colagem do supercontinente Rodínia (1,2-1,0 Ga) e estágios finais do Ciclo Orogênico Sunsás-Aguapeí (1320-1100 Ma). Sugere-se ainda que na verdade o Maciço Santa Clara seja formado por uma coalescência das três intrusões graníticas que são representadas pelos três magmas anteriormente descritos.

Mães obesas, filhotes obesos: estudo experimental

O aumento da obesidade materna pode refletir em efeitos deletérios na prole adulta, manifestos diferentemente de acordo com o gênero do indivíduo. Este trabalho teve como objetivo verificar a hipótese de que a obesidade materna provoca alterações metabólicas, na estrutura do tecido adiposo e hepático e mudanças de perfil inflamatório nas proles adultas de machos e fêmeas. Fêmeas C57BL/ 6 receberam dieta padrão (SC, 17% da energia proveniente do lipídeo) ou dieta hiperlipídica (HF; 49% da energia proveniente do lipídeo) durante oito semanas pré-gestacionais até a lactação. Após o desmame, os filhotes foram divididos nos grupos: SCM (machos), SCF (fêmeas), HFM (machos) e HFF (fêmeas). As características metabólicas foram avaliadas pela massa corporal (MC), glicemia de jejum, área sob a curva no teste oral de tolerância a glicose; concentrações de triglicerídes (TG) hepáticos e estimativa da esteatose hepática; análise plasmática de insulina, colesterol total (CT), triglicerídes (TG) e adipocinas; distribuição e análise morfológica do tecido adiposo e estado pró-inflamatório dos filhotes. Diferenças entre os grupos foram analisadas pelo Teste T não pareado (dados entre progenitoras e pares de grupos nas proles); one-way ANOVA com pós-teste de Tukey (para proles) e two-way ANOVA (efeito da dieta materna e gênero). O nível de significância adotado foi de P≤0,05. Progenitoras HF tiveram maior MC (+20%), glicemia elevada (+22%) e intolerância à glicose em comparação ao grupo SC. A partir da quarta semana, a MC mostrou-se maior nas proles HF, em ambos os gêneros, quando comparados às proles SC. Na 12 semana, a MC foi 20% maior no grupo HF macho e 30% maior no grupo HF fêmea do que seus controles (p<0,0001, ambos os gêneros). Intolerância à glicose foi observada em machos e fêmeas HF em relação aos seus contrapares SC (+20%, p<0,05). Proles HF demonstraram hepatomegalia com maior acúmulo de TG hepático, resultando em maior percentual de esteatose em machos (27%) e fêmeas HF (25%). Proles HF apresentaram incremento na adiposidade (+20%) e nos níveis de CT e TG do que seus congêneres SC. Níveis plasmáticos de leptina e insulina foram maiores, enquanto houve diminuição da adiponectina no grupo HF macho em relação ao grupo SC macho. Hipertrofia de adipócitos foi observada nas proles HF. TNF-alfa, IL-6 e leptina foram mais expressos em proles HF, porém diminuição na expressão de adiponectina foi evidenciada nas proles geradas por mães obesas. A luz do exposto, a dieta HF administrada em mães antes e durante períodos de gestação e lactação leva à obesidade materna que tem consequências na prole, tais como remodelamento do tecido adiposo, juntamente com alterações bioquímicas e metabólicas dos adipócitos, intensificando o estado pró-inflamatório da prole, em ambos os gêneros, na idade adulta.

High bandwidth multimode fiber links using subcarrier multiplexing in vertical-cavity surface-emitting lasers

The usage of subcarrier multiplexing (SCM) techniques to allow link transmission in excess of the specified fiber bandwidth is described. A series of 200-Mbit/s channels with carrier frequencies of up to more than twenty times the 3-dB fiber bandwidth have been successfully used, the maximum being limited by the available electronics. To assess the transmission of the fiber, digitally modulated channels are placed on high frequency carrier signals and then used to modulate a vertical-cavity surface-emitting lasers (VCSEL).

Transmission performance of adaptively modulated optical OFDM modems using subcarrier modulation over SMF IMDD links for access and metropolitan area networks.

Detailed investigations are undertaken, for the first time, of the transmission performance of recently proposed novel Adaptively Modulated Optical OFDM (AMOOFDM) modems using Subcarrier Modulation (AMOOFDM-SCM) in single-channel, SMF-based IMDD links without optical amplification and chromatic dispersion compensation. The cross-talk effect induced by beatings among subcarriers of various types is a crucial factor limiting the maximum achievable AMOOFDM-SCM performance. By applying single sideband modulation and/or spectral gapping to AMOOFDM-SCM, three AMOOFDM-SCM designs of varying complexity are proposed, which achieve >60Gb/s signal transmission over 20 km, 40 km and 60 km. Such performances are >1.5 times higher than those supported by conventional AMOOFDM modems.

Simple adaptively modulated optical OFDM modems using subcarrier modulation with input/output reconfigurability

Three novel designs of adaptively modulated optical orthogonal frequency division multiplexing modems using subcarrier modulation (AMOOFDM-SCM) are proposed, for the first time, each of which requires a single IFFT/FFT operation. These designs has a number of salient advantages including a significantly simplified modem configuration due to the involvement of a single IFFT/FFT operation, input/output reconfigurability, dynamic bandwidth allocation capability, cost reduction and system flexibility and performance robustness to variations in transmission link conditions. Investigations show that these three modems are capable of supporting >60Gb/s AMOOFDM-SCM signal transmission over 20km, 40km and 60km single-mode fibre-based intensity modulation and direct detection transmission links without optical amplification and chromatic dispersion compensation. Copyright © 2010 The authors.

Performance assessment of XACML authorizations for supply chain traceability web services

Service-Oriented Architecture (SOA) and Web Services (WS) offer advanced flexibility and interoperability capabilities. However they imply significant performance overheads that need to be carefully considered. Supply Chain Management (SCM) and Traceability systems are an interesting domain for the use of WS technologies that are usually deemed to be too complex and unnecessary in practical applications, especially regarding security. This paper presents an externalized security architecture that uses the eXtensible Access Control Markup Language (XACML) authorization standard to enforce visibility restrictions on trace-ability data in a supply chain where multiple companies collaborate; the performance overheads are assessed by comparing 'raw' authorization implementations - Access Control Lists, Tokens, and RDF Assertions - with their XACML-equivalents. © 2012 IEEE.

gcs-ma: a group communication system for mobile agents

Reliable messaging is a key component necessary for mobile agent systems. Current researches focus on reliable one-to-one message delivery to mobile agents. But how to implement a group communication system for mobile agents remains an open issue, which is a powerful block that facilitates the development of fault-tolerant mobile agent systems. In this paper, we propose a group communication system for mobile agents (GCS-MA), which includes totally ordered multicast and membership management functions. We divide a group of mobile agents into several agent clusters,and each agent cluster consists of all mobile agents residing in the same sub-network and is managed by a special module, named coordinator. Then, all coordinators form a ring-based overlay for interchanging messages between clusters. We present a token-based algorithm, an intra-cluster messaging algorithm and an inter-cluster migration algorithm to achieve atomicity and total ordering properties of multicast messages, by building a membership protocol on top of the clustering and failure detection mechanisms. Performance issues of the proposed system have been analysed through simulations. We also describe the application of the proposed system in the context of the service cooperation middleware (SCM) project.

含氰基有机化合物的等离子体聚合及电学性能研究

I、等离子体聚合TCNQ、TCNE薄膜采用内部电极、电容耦合式、钟罩型RF等离子体聚合装置，在不同的放电功率下，首次进行了TCNQ（四氰基二甲苯醌）、TCNE（四氰基乙烯）的等离子体聚合，并利用红外光谱（IR）、紫外光谱（UV）、元素分析、X线光电子能谱（XPS）对所得聚合物的化学结构进行了表征。结果表明，在TCNQ、TCNE的等离子体聚合物中存在着较大范围的π电子共轭结构体系。通过对其聚合物薄膜的电学性能研究结果发现，随聚合反应条件不同，所制得的聚合物膜电导率在10~（-10）～ 10~（-6）scm~(-1)范围内变化，并且发现这种等离子体聚合膜具有典型的p-型半导体特征，由这些等离子体聚合物薄膜制备的Al电极/聚合物膜/ITO电极夹层元件，在无光照射的暗状态时，都具有较优良的单向导电的整流特性，并且在白色光的照射下，能够产生光生电动势而显示出较好的光电转换特性。另外，这种聚合物薄膜还具有一定的光电导性。本实验通过研究放电功率对等离子体聚合物化学结构的影响时发现，在较低放电功率时，有利于聚合物中较大范围的π电子共轭结构体系的形成。相应的聚合物膜电学性能研究表明，在较低放电功率下制得的聚合物膜具有更优良的电学性能，如在5W低放电功率下制得的TCNQ聚合物薄膜的电导率可达10~（-6）scm~(-1)，并且由其制备的夹层元件显示出优良的整流特性，当在白色光照射下，光电转换效率可高达10~（-3）%， 这在目前有机太阳能电池研究中，也属相当优良的有机光电转换材料之列。II、起始单体的化学结构对聚合物膜的结构及电学性质影响利用与I同样的实验方法，选用了一些具有不同化学结构的含氰基有机化合物为起始单体[TCNQ、TCNB（四氰基苯）、邻苯二甲腈、TCNE、二氨基马来腈、乙腈]，进行了等离子体聚合，并研究了起始单体结构对聚合物化学结构及电学性质的影响。结果表明，含苯环的氰基化合物在等离子体聚合过程中，具有大π电子共轭结构的苯环保持较好，并能够通过打开C≡N三键向更大范围延续，结果导致相应的等离子体聚合物膜具有较高的电导率，并且由这些聚合物膜制备的Al/聚合物膜/ITO夹层元件显示出优良的整流特性和光电转换性能。相反，当起始单体中的H原子含量较高时，就会导致相应聚合物中π电子共轭链段较短，相应的聚合物也就显示出较差的电学性质。另外，为提高等离子体聚合膜的电学性能，还进行了TCNQ与铜的乙酰丙酮络合物（CuAA）的等离子体共聚合，结果发现聚合膜电学性能明显改善。III、在辉光放电中乙腈等离子体聚合反应历程的研究采用外部电极、电容耦合式、管状RF等离子体聚合装置，在不同放电功率下，不同等离子气体以及不同等离子气体/单体比的反应条件下进行了等离子体聚合。通过考察聚合物膜的淀积规律和红外光谱测试与元素分析提供的聚合物化学结构数据，研究了乙腈在辉光放电中的聚合反应历程。实验结果表明，在低能量下，乙腈的等离子体聚合主要是通过脱氢引发进行的，而在高能量下，通过打开C≡N三键而进行聚合的几率将增大。

高分子固体电解质

固体电解质是全塑固态电池不可缺少的一个组成部分，近年来得到了迅速的发展。高分子固体电解质由于质量轻，可塑性强，并具且良好的力学性能和机械加工性能，在固体电解质领域内越来越受到人们的重视和关注。高分子固体电解质一般是由聚醚类的高分子主体物和无机盐形成的复合物。聚氧化乙烯（PEO）是高分子主体物中比较优秀的代表，其盐复合物在高温（100 ℃）时电导率可达2 * 10~(-3)Scm~(-1)，但由于结晶，其室温电导率很低(10~(-8) ～ 10~(-7)Scm~(-1))，远远满足不了室温电池的要求。本工作的目的是利用接技和共聚对PEO进行改性，提高复合物室温电导率。主要工作和结论有下列几点：（1）采用二步法合成了列三种单体：CH_2-CH CH_2O(CH_2CH_2O)_nCH_3 (n = 0,1,2)，通过改进反应条件，提高了产物收率。（2）考察了不同烷基铝多元催化剂对上述单体聚合的催化性能，发现只有Al(i-Bu)_3-Zn(acac)_2-H_2O和AlEt_3-Hacac-H_2O对单体聚合的催化效果较好。（3）DSC分析的结果表明，上述单体的均聚物不易结晶；聚合物玻璃化温度分别为-64 ℃(n = 0)，-75 ℃ (n = 1)和-86 ℃(n = 2)，都比PEO(Tg = -57 ℃)低，这对提高复合物电导率应该是有利的。（4）利用环氧丙烷（Po）与环氧烷（Eo）共聚，大幅度降低了聚合物的结晶性，当共聚物中Po含量达到40％时，聚合物几乎是完全非晶的。（5）利用DSC、X－射线衍射、偏光显微镜等手段对均聚物和共聚物的 NaScN和LiClO_4复合物的聚集态结构进行了研究，发现复合物中没有结晶络合物相存在，这与PEO体系是不同的。复合物结晶度随聚合物结构和盐含量的不同而变化。（6）共聚改性是提高复合物室温电导率的有效手段。共聚物与NaScN和LiClO_4复合物在25 ℃时的电导率分别达到了5 * 10~(-5)Scm~(-1)和1.1 * 10~(-4)Scm~(-1)，与PEO体系相比提高了2 ～ 3个数量级。（7）梳状均聚物虽然结晶度和玻璃化温度都很低，但其盐复合物的室温电导率不高，只有10~(-6)Scm~(-1)数量级，这与我们预期的结果不一致。（8）聚合物一盐复合物的电导率随聚合结构以及盐的种类和含量的变化而不同。对于无机盐来说，阴离子相同时，复合物电导率随阳离子半径的增大而增大，随着盐浓度的变化，复合物电导率出现一个极大值。另外，成膜溶剂、水份等都对复合物电尼率有很大的影响。（9）考察了复合物电导率随温度的变化情况。高温(～100 ℃)时，复合物电导率都比PEO体系低，说明为提高复合物室温电导率而对PEO进行的改性是以牺牲其高温电导率为代价的。

新型含聚氧化乙烯结构侧链的硅氧烷梳状聚合和光解质的合成与表征

目前对高分子固体电解质的研究大多着眼于以聚氧化乙烯（PEO）为主体聚合物的各种碱金属盐络合物，大量研究表明，PEO是迄今为止络合效果最佳的高分子主体物，其盐络合物的高温电导率可达2 * 10~(-3) scm~(-1)。但在室温下由于PEO的结晶阻碍了离子的迁移，从而使其应用范围受到局限。本工作选用高柔顺性的聚硅氧烷作为骨架与低分子量聚醚接技合成出了一种新型的高分子固体电解质主体材料，并对其碱金属盐络合物的电性能进行了研究。