Lee Park Keong. / 據手稿本影印. / Thesis (M.A.)--香港中文大學硏究院教育學部. / Ju shou gao ben ying yin. / Includes bibliographical references: leaves 183-188. / Lee Park Keong. / Thesis (M.A.)--Xianggang Zhong wen da xue yan jiu yuan jiao yu xue bu. / Chapter 第一章 --- 導言 / Chapter 一、 --- 問題說明 --- p.1 / Chapter 二、 --- 有關文獻 --- p.3 / Chapter 三、 --- 研究問題 --- p.9 / Chapter 四、 --- 假設 --- p.14 / Chapter 第二章 --- 研究方法 / Chapter 一、 --- 研究對象與取樣 --- p.17 / Chapter 二、 --- 研究工具 --- p.18 / Chapter 三、 --- 研究設計 --- p.26 / Chapter 四、 --- 資料整理與分析 --- p.30 / Chapter 五、 --- 實驗程序的控制 --- p.31 / Chapter 第三章 --- 結果與討論 / Chapter 一、 --- 實驗一的結果與討論 --- p.35 / Chapter 二、 --- 實驗二的結果與討論 --- p.61 / Chapter 三、 --- 實驗三的結果與討論 --- p.78 / Chapter 四、 --- 其他結果與討論 --- p.83 / Chapter 第四章 --- 摘要檢討與建議 / Chapter 一、 --- 摘要 --- p.99 / Chapter 二、 --- 檢討 --- p.101 / Chapter 三、 --- 建議 --- p.104 / Chapter 第五章 --- 附錄 / Chapter 一、 --- 註釋 --- p.108 / Chapter 二、 --- 表目 --- p.109 / Chapter 三、 --- 實驗所用材料 --- p.111 / Chapter 四、 --- 實驗所得數據 --- p.145 / Chapter 五、 --- 數據圖 --- p.175 / Chapter 六、 --- 參考書目 --- p.183

A Multivalent entity, which could represent a protein, nanoparticle, polymer, virus or a lipid bilayer, has the ability to form multiple bonds to a substrate. Hence, a multivalent interaction can be strong, even if the individual bonds are weak. However, much more interestingly, multivalency enables the design of highly specific interactions using non-specific individual bonds. We attempt to rationalise multivalent effects using simple physical models complemented with numerical simulations. Based on physiochemical characteristics of multivalent binders, we aim to predict the overall strength of interaction and its sensitivity to variation in parameters. We start with a simple model of homo-multivalency, where all bonds are equivalent. Such systems can exhibit a super-selective response, which denotes the high sensitivity of the strength of multivalent binding to the number of accessible binding sites on the target surface. We present a theoretical analysis of systems of multivalent particles and show that a certain degree of disorder is necessary for super-selective behaviour. Moreover, we formulate a set of simple design rules for multivalent interactions that yield optimal selectivity. In the second stage, we expand the model to hetero-multivalency, accounting for multiple distinct types of binding partners. We consider targeting of cells based on a density profile of different membrane receptors types and demonstrate, that speci city towards a desired receptor density profile can be obtained. Hence, cells can be reliably targeted in the absence of specific markers. Crucially, we show that for optimal selectivity, individual bonds must be weak. Finally, we add information about specific geometry and positions of binding sites on the multivalent entity. We focus on molecular imprinting; the process whereby a polymer matrix is cross-linked in the presence of template molecules. The cross-linking process endows the polymer matrix with a chemical ‘memory’, such that the target molecules can subsequently be recognised by the matrix. We show how the binding multivalency and the polymer material properties affect the efficiency and selectivity of molecular imprinting.

Made available in DSpace on 2014-06-11T19:22:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-18Bitstream added on 2014-06-13T19:07:31Z : No. of bitstreams: 1 costa_sia_me_botfca.pdf: 984792 bytes, checksum: cb67fdcc6792f93f5896eec931c1f44a (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este trabalho teve como objetivo avaliar a seletividade do herbicida saflufenacil de forma isolado e em mistura, aplicado em pós-emergência inicial sobre 10 variedades de cana-de-açúcar em condição de cana-soca. O experimento foi instalado no município de Botucatu/SP. O delineamento experimental utilizado foi o de blocos casualizados em parcelas subdivididas com quatro repetições, sendo as variedades dispostas nas parcelas e os herbicidas nas subparcelas. Os tratamentos utilizados foram: saflufenacil + Assist (0,07 kg ha-1 + 0,5% v/v); saflufenacil + Break Thru (0,140 kg ha-1 + 0,05% v/v); saflufenacil (0,280 kg ha-1) e ametryne + clomazone (3,0 + 2,0 L i. a. ha-1), aplicados aos 49 DAC (dias após o corte), além de uma testemunha sem aplicação. As plantas encontravam-se por ocasião da aplicação com 2 a 4 folhas. As dez variedades utilizadas foram: SP83-2847, SP80-3280, RB855453, SP80-1842, SP89-1115, RB867515, PO8862, RB855156, SP80-1816 e SP81-3250. Para a aplicação das caldas herbicidas utilizou-se um pulverizador costal pressurizado a CO2 equipado com barra de aplicação com seis pontas Teejet XR 110 02 VS, à 200 kPa no volume de aplicação de 200 L ha-1. As avaliações visuais de controle foram realizadas aos 3, 7, 15, 21, 30, 45 e 60 dias após a aplicação. As injúrias visuais observadas nas plantas de cana-de-açúcar foram dependentes da variedade analisada e dos herbicidas e doses em teste. Todos os tratamentos químicos foram seletivos as diferentes variedades estudadas, não afetando o rendimento de colmos / This study aims to evaluate the selectivity of the herbicide saflufenacil applied alone and mixed, in post-emergence over ten sugarcane varieties in the second year after planting. The experiment was carried out in Botucatu/SP. The experimental design was a randomized split plot with for replications, and the varieties in the plot and subplot herbicides. The treatments were: saflufenacil + Assist (0.07 kg ha-1 + 0,5 v/v); saflufenacil + Break Thru (0.140 kg ha-1 + 0.05% v/v); saflufenacil (0.280 kg ha-1) and ametryne + clomazone (2.0 + 3.0 L ha-1) applied to the 49 DAH (days after first harvest), and a control without application. The plants were at 2 to 4 leaves in the application time. The varieties were: SP83-2847, SP80- 3280, RB855453, SP80-1842, SP89-1115, RB867515, PO-8862, RB855156, SP80-1816 and SP81-3250. For herbicide application was used the Teejet XR 11002 VS spray equipment with six spray nozzles type, at 200 kPa and, 200 L ha-1 spray volume. The visual injuries observed in plants of sugarcane were dependent of varieties and the herbicides and, doses tested. All chemical treatments tested were selective to different varieties studied, without affecting the crop production

Made available in DSpace on 2017-07-10T17:37:10Z (GMT). No. of bitstreams: 1 Everton Ricardi Lozano da Silva.pdf: 1285547 bytes, checksum: 985ef107fc92d11abb8864885e596668 (MD5) Previous issue date: 2006-03-17 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The objective of this research was evaluation "in vitro" the effect of fungicides and herbicides on Bacillus thuringiensis var. kurstaki (Btk). The five fungicides: epoxiconazole, fentin hydroxide, azoxystrobin, tebuconazole and carbendazim, and five herbicides: sulfentrazone, lactofen, imazethapyr, fenoxaprop and metribuzin were tested at two concentrations, on cells and spores, in nutrient agar (NA) - solid medium (SM), and in nutrient broth (NB) - liquid medium (LM), in addition to their metabolization (MT) by Btk. For cells, the phytosanitary products in NA were tested incorporated into the medium and on filter paper disks impregnated with the products. The evaluation consisted, respectively, of the number of CFU/mL and of the formation of an inhibition halo. For cells, the Bt+products+NB mixture was incubated in Erlenmeyer flasks (30± 2°C, 150rpm, 24h)an then the NB was diluted and inoculated onto NA; the number of CFU/mL was evaluated. The MT and spore tests were performed in liquid medium (water for MT and NB for spores). The effects of the products varied with the category (fungicide and herbicide), their concentrations, technique used, contact time, and developmental stage of the pathogen. The LM test is the most indicated to evaluate the effect of the products on cells. It was observed that most fungicides were compatible with cells, and only epoxiconazole and azoxystrobin were metabolized. The herbicides, independents of the concentrations, were incompatible with cells, and only sulfentrazone and imazethapyr were metabolized. Fentin hydroxide was the only product incompatible with spore / Objetivou-se comparar técnicas para a avaliação in vitro do efeito de fungicidas e herbicidas sobre Bacillus thuringiensis var. kurstaki (Btk). Foram testados cinco fungicidas: epoxiconazole, fentin hidróxido, azoxystrobin, tebuconazole e carbendazin, e cinco herbicidas: sulfentrazone, lactofen, imazethapyr, fenoxaprop e metribuzin, em duas concentrações, sobre células e esporos, em ágar nutriente (AN) - sólido (MS) e caldo nutriente (CN) - líquido (ML), além da metabolização (MT) destes por Btk. Para células, em AN os fungicidas foram testados incorporados ao meio e em discos de papel-filtro impregnados nos produtos. Avaliou-se, respectivamente, as UFC/mL e a formação de halo de inibição. Para células, a mistura Bt+produtos+CN foi incubada em erlemmeyers (30± 2°C, 150rpm, 24h), e em seguida, o meio CN foi diluído e inoculado em AN, avaliando-se o número de UFC/mL. Os testes de MT e esporos foram realizados em líquido (água para MT e CN para esporos). O efeito dos produtos variou conforme a categoria destes (fungicida e herbicida), concentrações, técnica, tempo de contato e fase/estágio do desenvolvimento do patógeno. O teste ML é o mais indicado para a avaliação do efeito em células, sendo observado que a maioria dos fungicidas mostrou-se compatível às mesmas, e apenas epoxiconazole e azoxystrobin foram metabolizados. Os herbicidas, independentes das concentrações, foram incompatíveis com as células, e somente sulfentrazone e imazethapyr foram metabolizados. Fentin hidróxido foi o único produto incompatível com esporos

Helicoverpa armigera é uma espécie que até 2013 era considerada praga quarentenária A1 no Brasil. Tratamentos com inseticidas são indispensáveis para o manejo de H. armigera em quase todas as culturas do mundo. Uma alternativa à utilização de inseticidas sintéticos para o controle de pragas é o uso de parasitoides do gênero Trichogramma. Em consideração a grande quantidade de aplicações de agroquímicos no sistema de produção de grãos, torna-se essencial avaliar a seletividade dos inseticidas utilizados, garantindo informações que auxilie na manutenção do T. pretiosum na área, podendo potencializar o controle biológico de H. armigera, sendo isto, importante para o estabelecimento do manejo integrado de pragas nas grandes culturas. Portanto, objetivou-se com esse trabalho: estudar a toxicidade aguda e a persistência de inseticidas sobre o parasitoide; estudar o efeito de inseticidas sobre a fase pupal do parasitoide; determinar a interferência dos inseticidas na capacidade de parasitismo. Dos inseticidas testados em condições laboratoriais, Nomolt®, Avatar®, Belt®, Premio® e Intrepid® foram considerados inócuos para adultos. Lorsban® e Engeo Pleno® são nocivos à fase de pupa, enquanto Acefato®, Pirate® e Belt® apesar de inócuos afetam as gerações seguintes. Pirate®, Lorsban® e Engeo Pleno interferem na capacidade de parasitismo, e Acefato® tem efeito deletério na geração que tem contato com o resíduo. Os inseticidas Nomolt®, Avatar®, Belt®, Acefato®, Premio® e Intrepid® foram classificados como inseticidas de vida curta (classe 1). Lorsban® tem efeito moderadamente persistente (classe 3) e Engeo Pleno® e Pirate® classificados como persistentes (classe 4). Portanto, visando um bom programa de MIP, deve-se optar pelo uso de inseticidas seletivos, ou inseticidas nocivos para adultos do parasitoide podem ser utilizados no campo desde que estes não estejam ocorrendo naturalmente ou que não coincida com épocas de liberação do mesmo. / Helicoverpa armigera is a specie that until 2013 was considered A1 quarantine pest in Brazil. Treatments with insecticides are indispensable for the management of H. armigera in almost every crops in the world. An alternative to the use of synthetic insecticides for pest control is the use of parasitoids of the genus Trichogramma. Considered the large number of agrochemical applications in grain yield, it is essential assess the selectivity of insecticides used, providing informations to assist in the maintenance of T. pretiosum in the area and can enhance the biological control of H. armigera, this being important for the establishment of integrated pest management in field crops. Therefore, the aim of this work was study the acute toxicity and the duration of the harm effects of insecticides on the parasitoid, study the effect of insecticides on the pupal stage of the parasitoid and determine the interference of insecticides on the parasitism capacity. Insecticides tested in laboratory conditions, Nomolt®, Avatar®, Belt®, Premio® and Intrepid® were considered innocuous to the adults. Lorsban® and Engeo Pleno® were harmful to the pupal stage, while Acefato®, Pirate® and Belt® although were considered innocuous they affect the next generations. Pirate®, Lorsban® and Engeo Pleno® interfered on the parasitism capacity, and Acefato® have a deleterious effect on the generation that has contact with the insecticide residue. The insecticides Nomolt®, Avatar®, Belt®, Acefato®, Premio® and Intrepid® were classified as short live (class 1). Lorsban® was moderately persistent (class 3) and Engeo Pleno® and Pirate® were classified as persistent (Class 4). Therefore, for an effective IPM program, it is important to use the selective insecticides. Insecticides that were harmful to the parasitoid adults could be used in the field, provided that the parasitoids do not occur naturally and the chemical applications do not coincide with the parasitoids release.

In our efforts to engineer a DNA binding and cleaving protein with greater sequence discrimination, we have designed dimeric proteins derived from engrailed homeodomain and calmodulin. Previous research by our group has shown that a hydrolytically active lanthanide binding site can be incorporated into a DNA binding motif. To understand protein-DNA interaction and improve the sequence selectivity of the chimeric complex, two lanthanide-binding homodimers were designed and expressed. One of the dimers, F2, is coupled together by a flexible polypeptide linker and the other, R7C, is a disulfide cross-linked cysteine mutant at the N-terminus. Studies of fluorescence of tryptophan residues document that the overall affinity for lanthanide and calcium is similar to traditional EF-hand peptides (1-10 μM). Metal titrations monitored by circular dichroism (CD) revealed that the secondary structures of the dimers contained a lower degree of -helicity than the designed monomeric protein due to additional modifications, but because of their flexibility and their two active-site domain, hydrolytic activity was several folds faster than our previously designed proteins and peptides. Unlike earlier reports on our chimeras, F2 also demonstrated the capability to hydrolyze DNA in the presence of some biological relevant metal ions suggesting different cleavage mechanisms were carried out. Extensive DNA sequencing studies on cleavage patterns with oligonucleotide duplexes confirmed the unique sequence selectivity and kinetic properties of F2. Two engrailed homeodomain target sites, TAATTA, were favored for hydrolytic activity corresponding to one domain acting as a DNA anchor on the first target site while the other was an "opportunist" at recognizing the second site. Nonetheless, the hydrolytic behavior at the phosphodiester bond on a specific dsDNA sequence is in good agreement with the behavior of restriction endonucleases. Unlike restriction enzymes, metallated F2 has not only demonstrated the ability to cleave DNA plasmid, but it also excises the entire nucleotide on a selected sequence. This homodimer is the first example of an active and selective hydrolytic artificial nuclease based on the modular turn substitution design approach that can be a potential template for genomic modification.

Local descriptors are increasingly used for the task of object recognition because of their perceived robustness with respect to occlusions and to global geometrical deformations. We propose a performance criterion for a local descriptor based on the tradeoff between selectivity and invariance. In this paper, we evaluate several local descriptors with respect to selectivity and invariance. The descriptors that we evaluated are Gaussian derivatives up to the third order, gray image patches, and Laplacian-based descriptors with either three scales or one scale filters. We compare selectivity and invariance to several affine changes such as rotation, scale, brightness, and viewpoint. Comparisons have been made keeping the dimensionality of the descriptors roughly constant. The overall results indicate a good performance by the descriptor based on a set of oriented Gaussian filters. It is interesting that oriented receptive fields similar to the Gaussian derivatives as well as receptive fields similar to the Laplacian are found in primate visual cortex.

No description available.

A new format for microfluidic based DNA biosensors is presented in which the biorecognition element (single stranded DNA probes) is immobilized as a continuous density gradient of probes along the length of a microfluidic channel instead of a standard array format commonly used in microarray technologies or DNA based biosensors. The development of continuous density gradients of immobilized probe was achieved by electrokinetically subjecting probes that were terminated with an appropriate functional group for a surface coupling reaction to increasing convective velocity along the length of the microfluidic channel. This gradient format was able to discriminate between a fully complementary target and one containing 3 BPM based on the spatial pattern of hybridization for picomole quantities of DNA targets. Temperature mediated destabilization of DNA hybrids demonstrated that the density of immobilized probes plays an important role in the thermodynamic stability of DNA hybrids. In addition, it was found that efficiency, selectivity and melt temperature of DNA hybrids for surface based hybridization is dependent on the density of the probe molecules.

A new format for microfluidic based DNA biosensors is presented in which the biorecognition element (single stranded DNA probes) is immobilized as a continuous density gradient of probes along the length of a microfluidic channel instead of a standard array format commonly used in microarray technologies or DNA based biosensors. The development of continuous density gradients of immobilized probe was achieved by electrokinetically subjecting probes that were terminated with an appropriate functional group for a surface coupling reaction to increasing convective velocity along the length of the microfluidic channel. This gradient format was able to discriminate between a fully complementary target and one containing 3 BPM based on the spatial pattern of hybridization for picomole quantities of DNA targets. Temperature mediated destabilization of DNA hybrids demonstrated that the density of immobilized probes plays an important role in the thermodynamic stability of DNA hybrids. In addition, it was found that efficiency, selectivity and melt temperature of DNA hybrids for surface based hybridization is dependent on the density of the probe molecules.