Avaliação in vitro de duas resinas macias para reembasamento de próteses modificadas pela incorporação de clorexidina

Resinas macias para reembasamento de próteses são largamente utilizadas após cirurgias para estabilizarem a prótese e condicionarem o tecido, aguardando a completa cicatrização. É importante que o material não seja facilmente colonizado por biofilme oral e se possível, evite a contaminação do sítio cirúrgico. Objetivou-se avaliar o efeito da incorporação de clorexidina às resinas acrílicas macias para o reembasamento de próteses totais, através de análises de liberação, citotoxicidade e efeito inibitório de um biofilme de C. albicans. Foram confeccionados corpos de provas (CDPs) com as resinas Trusoft e Coe-soft, com incorporação de 0%, 0,5%, 1,0% e 2,0% de clorexidina, totalizando 8 grupos. A liberação de clorexidina foi avaliada através da mensuração da mudança na densidade óptica da solução de armazenamento, na qual ficaram imersos os CDPs, por espectrometria UV, a cada 48 horas, durante 40 dias. A citotoxicidade celular foi avaliada em fibroblastos (linhagem L929), que ficaram 24 horas em contato com meio de cultura no qual os CDPs ficaram previamente imersos, pela técnica de absorção de corante vermelho neutro após 24, 48 e 72 horas e semanalmente até o 28 dia. E, por fim, a atividade antifúngica contra a C. albicans (ATCC 10231) foi avaliada de duas maneiras: (1) teste de difusão em ágar, no qual os CDPs foram colocados em placas de BHI previamente inoculadas com C. albicans, com medição do halo de inibição após 48 horas de incubação a 37C; (2) a avaliação da inibição da formação de um biofilme de C. albicans sobre a superfície dos CDPs pela quantificação por metil tetrazólio (MTT) a cada 48 horas, durante 22 dias, com leitura feita em espectrofotômetro de UV. Os dados obtidos foram inseridos no programa SigmaStat (versão 3.1, USA) para realizar as análises estatísticas. As diferenças estatísticas foram determinadas por análises de variâncias do tipo ANOVA e todos os procedimentos para comparações múltiplas pareadas foram feitos utilizando-se o método Holm-Sidak, com nível de significância global igual a 0,05. A clorexidina adicionada às resinas testadas foi capaz de ser liberada para o meio de armazenagem, proporcionalmente à quantidade de clorexidina incorporada, porém com diferentes cinéticas de liberação entre as resinas, visto que a Trusoft libera até 71% do total de clorexidina liberada nas primeiras 48 horas e a Coe-soft, até 44%. Ambas as resinas com incorporação de clorexidina apresentaram efeito citotóxico adicional, se comparadas às resinas sem clorexidina, porém para a Coe-soft não houve diferença estatística dos valores, apenas para a Trusoft (p<0,001). Ocorreu formação de halo de inibição proporcionalmente às concentrações de resinas adicionadas, com maiores halos para a resina Trusoft (p<0,001), e sem formação de halo para as resinas sem clorexidina; a inibição da formação de biofilme, realizada somente com a resina Coe-soft, mostrou total inibição durante 8, 12 e 16 dias, para a incorporação de 0,5%, 1,0% e 2,0% respectivamente, sendo uma diminuição estatisticamente significativa (p<0,001) em relação à resina sem incorporação de clorexidina, que não apresentou inibição do biofilme.

Global analysis of mRNA half-lives and de novo transcription in a dinoflagellate, Karenia brevis

Dinoflagellates possess many physiological processes that appear to be under post-transcriptional control. However, the extent to which their genes are regulated post-transcriptionally remains unresolved. To gain insight into the roles of differential mRNA stability and de novo transcription in dinoflagellates, we biosynthetically labeled RNA with 4-thiouracil to isolate newly transcribed and pre-existing RNA pools in Karenia brevis. These isolated fractions were then used for analysis of global mRNA stability and de novo transcription by hybridization to a K. brevis microarray. Global K. brevis mRNA half-lives were calculated from the ratio of newly transcribed to pre-existing RNA for 7086 array features using the online software HALO (Half-life Organizer). Overall, mRNA half-lives were substantially longer than reported in other organisms studied at the global level, ranging from 42 minutes to greater than 144 h, with a median of 33 hours. Consistent with well-documented trends observed in other organisms, housekeeping processes, including energy metabolism and transport, were significantly enriched in the most highly stable messages. Shorter-lived transcripts included a higher proportion of transcriptional regulation, stress response, and other response/regulatory processes. One such family of proteins involved in post-transcriptional regulation in chloroplasts and mitochondria, the pentatricopeptide repeat (PPR) proteins, had dramatically shorter half-lives when compared to the arrayed transcriptome. As transcript abundances for PPR proteins were previously observed to rapidly increase in response to nutrient addition, we queried the newly synthesized RNA pools at 1 and 4 h following nitrate addition to N-depleted cultures. Transcriptome-wide there was little evidence of increases in the rate of de novo transcription during the first 4 h, relative to that in N-depleted cells, and no evidence for increased PPR protein transcription. These results lend support to the growing consensus of post-transcriptional control of gene expression in dinoflagellates.

小波分析和人工神经网络在生态学研究中的应用

墨西哥帽子小波和Morlet小波在生态格局分析中的应用 本研究采用Monte Carlo方法，探讨了对小波分析的格局进行统计显著性检验的普遍方法。为了更好利用小波分析和了解两个常用小波--墨西哥帽子小波和Morlet小波在格局分析中的优缺点，用生态学研究中常见的4个模拟格局和东灵山辽东栎林的样带数据对这两个常用小波的特性进行了分析和比较。研究结果表明：墨西哥帽子小波能较好地分析样带中的斑块和间隙以及它们的位置信息，Morlet小波能较好地分析样带中尺度及其位置信息。不同的小波通常在尺度分析和斑块和间隙分析之间有平衡，所以最好的方法是结合两种小波的优点。小波分析在处理生态数据时，受所使用小波本身特性的制约。用墨西哥帽子小波进行格局分析时，小波能量谱的等值图上不同格局所对应的峰有可能相互重叠，当所分析的多尺度格局的规模差别不大时，所分析格局规模所对应的峰可能相互融合。这些小波能量谱的等值图上不同格局所对应峰的重叠和融合可能会导致格局分析量图上多个峰的相互融合和屏蔽。所以在使用小波分析做格局研究时，也应尽可能地结合小波能量谱和量图上的信息，以得到较全面和精确的格局分析信息。本研究的结论能为小波分析的应用提供指导。 应用二维小波分析对暖温带阔叶林辽东栎更新格局的研究 本研究介绍了一种二维网格空间数据分析方法一二维小波分析。该方法不仅能分析格局的等级结构，而且也能得到所分析结构的位置信息。小波系数等值图上不同格局规模的斑块和间隙可直接和不同尺度上的生态过程和生境条件相联系。小波方差从二维小波分析导出，小波方差可将四维的小波系数降至二维的小波方差函数，并量化所分析格局规模对整个格局的贡献。本研究用三个模拟格局分析了二维小波的特性及二维墨西哥帽子小波和Halo小波的特性。因为自身的特性，Halo小波比墨西哥帽子小波能提供更高的分辨率。本研究也将二维小波分析应用于暖温带阔叶林的辽东栎更新格局研究中，分析的结果表明：辽东栎的更新发生在辽东栎成树斑块和林窗斑块重叠区域。 用交互验证和独立验证来测试神人工经网络模拟水稻分檗动态的泛化能力 人工神经网络不是基于对所模拟过程的理解，而是依赖于对所分析数据的内部结构。所以人工神经网络通常被认为是经验模型而不能外推，而且在训练数据和验证数据的范围之外肯定不能精确地预测所模拟的过程。本研究通过对交互验证和独立验证神经网络模型性能的比较，测试了神经网络模型在预测水稻分檗动态方面的泛化能力。同时，也对几种提高神经网络泛化能力的技术进行了比较。研究结果表明：在训练数据的变量范围内，神经网络在预测水稻分檗动态方面具有泛化能力。较少的训练数据样本导致了对训练数据过度吻合的和不具泛化能力的神经网络。要能使神经网络在预测水稻分檗动态方面具有泛化能力，训练数据的样本量至少9倍于神经网络的权值数目。当神经网络有多个输入变量且训练数据不足以保证神经网络的泛化能力时，建议在训练之前，采用主成分分析、对应分析及类似技术压缩输入变量的个数。在压缩输入变量的个数之后，如果训练数据的样本量还不足以保证神经网络的泛化能力，就应采用提高神经网络泛化能力的技木，如：jittering和强制训练停止等，特别是神经网络与机理模型的复合模型。因为神经网络的泛化能力问题具有普遍性，所以我们的研究结论不只是适用于水稻分檗动态的预测，也适用于其它的农业和生态神经网络模型。

Spoilage bacteria of Penaeus indicus

Bacteria isolated from raw (untreated and unprocessed) prawn (Penaeus indicus) stored at 28±2°C, 4°C and-18°C were tested for spoilage potential, namely, production of protease, lipase, amylase, reduction of trimethylamineoxide (TMAO) to trimethylamine (TMA), production of off odours from flesh broth and halo zone around the colony grown on flesh agar. About 63 % of the total isolates tested were potential spoilers. Members of Vibrio, Pseudomonas and Acinetobacter were found to be dominant potential spoilers at all temperatures.

Experimental study of two-proton correlated emission from S-29 excited states

An experiment of a S-29 beam bombarding a Au-197 target at an energy of 49.2 MeV/u has been performed to study the two-proton correlated emission from S-29 excited states. Complete-kinematics measurements were carried out in the experiment. The relative momentum, opening angle, and relative energy of two protons, as well as the invariant mass of the final system, were deduced by relativistic-kinematics reconstruction. The Si-27-p-p coincident events were picked out under strict conditions and the phenomenon of p-p correlations was observed among these events. The mechanisms of two-proton emission were analyzed in a simple schematic model, in which the extreme decay modes like He-2 cluster emission, three-body phase-space decay, and two-body sequential emission were taken into account. Associated with the Monte Carlo simulations, the present results show that two protons emitted from the excited states between 9.6 MeV and 10.4 MeV exhibit the features of He-2 cluster decay with a branching ratio of 29(-11)(+10)%.

Angular dispersion and deflection function for heavy ion elastic scattering

The differential cross sections for elastic scattering products of F-17 on Pb-208 have been measured. The angular dispersion plots of ln(d sigma/d theta) versus theta(2) are obtained from the angular distribution of the elastic scattering differential cross sections. Systematical analysis on the angular dispersion for the available experimental data indicates that there is an angular dispersion turning angle at forward angular range within the grazing angle. This turning angle can be clarified as nuclear rainbow in classical deflection function. The exotic behaviour of the nuclear rainbow angle offers a new probe to investigate the halo and skin phenomena.

Probing the medium effect and isospin dependence of the in-medium nucleon-nucleon cross section in heavy ion collisions

Probing in-medium nucleon-nucleon (NN) cross section sigma(1)(NN)(alpha) in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum- dependent interaction (IMDI(tau)). It is found that there are the very obvious medium effect and the sensitive isospin- dependence of nuclear stopping R on the in-medium NN cross section sigma(1)(NN)(alpha) in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, R induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of R on the medium effect of sigma(1)(NN)(alpha) in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of R's in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of sigma(1)(NN)(alpha) because of adding a new judgement.

Elastic scattering angular dispersion of weakly bound nucleus F-17

The differential cross-sections for elastic scattering of F-17 and O-17 on Pb-208 have been measured at Radioactive Ion Beam Line at Lanzhou (RIBLL). The variation of the logarithms of differential cross-sections with the square of scattering angles, viz. angulax dispersion plot, shows clearly that there exists a turning point in the range of small scattering angles (6 degrees-20 degrees) for F-17 due to its exotic structure, while no turning point was observed for O-17. The experimental results have been compared with previous data of other groups. Systematical analysis on the available data seems to conclude that there is an exotic behavior of elastic scattering angular dispersion of weakly bound nuclei with halo or skin structure as compared with that of the stable nuclei. Therefore the fact that the turning point of the elastic scattering angular dispersion plot appears at small angle for weakly bound nuclei can be used as a new probe to investigate the halo and skin phenomenon.

Exotic behavior of elastic scattering differential cross-sections of weakly bound nucleus F-17 at small angles

The differential cross-sections for elastic scattering of F-17 and O-17 on Pb-208 have been measured at Radioactive Ion Beam Line at Lanzhou (RIBLL). The variation of the logarithms of differential cross-sections with the square of scattering angles shows clearly that there exists a turning point in the range of small scattering angles (6 degrees-20 degrees) for F-17 having exotic structure, while no turning point was observed in the O-17 elastic scattering. The experimental results have been compared with previous data. Systematical analysis on the available data seems to conclude that there is an exotic behavior of elastic scattering differential cross-sections of weakly bound nuclei with halo or skin structure as compared with that of the ordinary nuclei near stable line. Therefore the fact that the turning point of the logarithms of differential cross-sections appears at small angle for weakly bound nuclei could be used as a new probe to investigate the halo and skin phenomenon.

Exotic behaviour of angular dispersion of weakly bound nucleus F-17 at small angles

The differential cross sections of F-17 and O-17 elastic scattering products on Pb-208 have been measured at the Radioactive Ion Beam Line at Lanzhou (RIBLL). Two angular dispersion plots of ln(d sigma/d theta) versus theta 2 are obtained from the angular distribution of the elastic scattering differential cross sections. The angular dispersion plot exhibits a clear turning point for F-17 in the range of small scattering angles 6 degrees-20 degrees due to its exotic structure, but for O-17, the turning point is not observed in the same angular range. The experimental results have been compared with previous data of other groups. Systematical analysis on the available data supports the above conclusion that there is an exotic behaviour of the angular dispersion plot of weakly bound nuclei with halo or skin structure as compared with that of the ordinary nuclei near stable line. Therefore the turning point of the angular dispersion plot appears at small angle for weakly bound nuclei with halo or skin structure, and can be used as a new probe to investigate the halo and skin phenomena of weakly bound nuclei.

Production cross section of neutron cluster from the reaction of light neutron rich nuclei

Within the Boltzmann-Langevin equation, the neutron cluster production cross sections in the reactions induced by Be-14, He-8, He-6, Li-11, B-17, Be-11, C-19 on C-12 at 35MeV/u were studied. The experimental data for (4)n production cross section from Be-14+C-12 at 35MeV/u can be reproduced. It is found that the production cross section of neutron cluster is large in the reaction that the projectile has more halo nucleons. And the projectiles with big mass number are easy to produce the neutron cluster, when they have the same number of halo nucleons. The neutron cluster is probably mainly from the halo nucleons of projectile.