Surface mining of coal in the country leaves a lot of damage. This type of mining is characterized by the creation of large external dumps. The dumps often contain substrates with toxic substances or substances which become toxic after reaction with air. These substrates are toxic to plants and edaphon. This work is intended to show what properties of substrates are important for phytotoxicity. The location of research was selected including 3 different kinds of substrates, terrain unevenness and a lagoon in the middle. Coordinate grid has been created on the selected location. At each point a test was conducted with plant Sinapis alba and biomass was extracted from a naturally growing vegetation. Further, at the points substrates were collected and values of pH, conductivity and arsenic were measured. Test with plant Sinapis alba was repeated in the laboratory conditions as well. On site GPS coordinates were measured for the mathematical model created in ArcGIS. Experiment has shown the importance of the type of substrate and the geologic description, and then the association between dejection, value of pH and conductivity. Conductivity and pH levels also correlate with the germination Sinapis alba and biomass of naturally growing vegetation.

The aim of this work is to describe North Bohemia brown coal (lignite) basin, as well as history of coal mining, development of this landscape and particulary the restoration of damaged landscape and nature. Theoretical part of my work summarizes the issueof recultivations, included history, types of reclamation, vanished settlements and significant exaples of recultivation. All of it is focused on region around North Bohemian city Most. Practical part's goal is to create an educational programme to increase knowledge of second degree Grammar school pupils about recultivations and to involve them in care about surrounding nature. Teaching programme was performed and results were statistically evaluated. Keywords Recultivation, Reclamation, Brown coal basin, Educational programme. Použité zkratky v AJ: SHP - North Bohemian lignite basin SHR - North Bohemian lignite basin

Topology studies the geometric properties of spaces that are preserved by continuous deformations. Manifolds are the main examples of topological spaces, with the local properties of Euclidean space in an arbitrary dimension n. They are the higher dimensional analogs of curves and surfaces. For example a circle is a one-dimensional manifold. Balloons and doughnuts are examples of two-dimensional manifolds. A balloon cannot be deformed continuously into a doughnut, so we see that there are essential topological differences between them. An "invariant" of a topological space is a number or an algebraic structure such that topologically equivalent spaces have the same invariant. For example the essential topological difference between the balloon and the doughnut is calculated by the "Euler characteristic", which is 2 for a balloon and 0 for a doughnut. In this thesis I investigate the relation between three different but related invariants of manifolds with dimension divisible by 4: the signature, the Brown-Kervaire invariant and the Arf invariant. The signature invariant takes values in the set (...;-3;-2;-1; 0; 1; 2; 3; ...) of integers. In this thesis we focus on the signature invariant modulo 8, that is its remainder after division by 8. The Brown-Kervaire invariant takes values in the set (0; 1; 2; 3; 4; 5; 6; 7). The Arf invariant takes values in the set (0; 1). The main result of the thesis uses the Brown-Kervaire invariant to prove that for a manifold with signature divisible by 4, the divisibility by 8 is decided by the Arf invariant. The thesis is entirely concerned with pure mathematics. However it is possible that it may have applications in mathematical physics, where the signature modulo 8 plays a significant role.

Cassava brown streak disease (CBSD) threatens food and economic security for smallholder farmers throughout East and Central Africa, and poses a threat to cassava production in West Africa. CBSD is caused by two whitefly-transmitted virus species: Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) (Genus: Ipomovirus, Family Potyviridae). Although varying levels of tolerance have been achieved through conventional breeding, to date, effective resistance to CBSD within East African cassava germplasm has not been identified. RNAi technology was utilized to integrate CBSD resistance into the Ugandan farmer-preferred cassava cultivar TME 204. Transgenic plant lines were generated expressing an inverted repeat construct (p5001) derived from coat-protein (CP) sequences of CBSV and UCBSV fused in tandem. Northern blots using probes specific for each CP sequence were performed to characterize 169 independent transgenic lines for accumulation of CP-derived siRNAs. Transgenic plant lines accumulating low, medium and high levels of siRNAs were bud graft challenged with the virulent CBSV Naliendele isolate alone or in combination with UCBSV. Resistance to CBSD in the greenhouse directly correlated to levels of CP-derived siRNAs as determined by visual assessment of leaf and storage root symptoms, and RT-PCR diagnosis for presence of the pathogens. Low expressing lines were found to be susceptible to CBSV and UCBSV, while medium to high accumulating plant lines were resistant to both virus species. Absence of detectable virus in the best performing p5001 transgenic lines was further confirmed by back-inoculation via sap or graft challenge to CBSD susceptible Nicotiana benthamiana and cassava cultivar 60444, respectively. Data presented shows robust resistance of transgenic p5001 TME 204 lines to both CBSV and UCBSV under greenhouse conditions. Levels of resistance correlated directly with levels of transgene derived siRNA expression such that the latter can be used as predictor of resistance to CBSD.

Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs, but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here, we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-K-s = 2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using the Hubble Space Telescope (HST) time-resolved grism spectroscopy, we find a best-fit rotational period (13.20 +/- 0.14 hr) with a larger amplitude at 1.1 mu m than at 1.7 mu m. This is the third-largest near-infrared variability amplitude measured in a brown dwarf, demonstrating that large-amplitude variations are not limited to the L/T transition but are present in some extremely red L-type dwarfs. We report a tentative trend between the wavelength dependence of relative amplitude, possibly proxy for small dust grains lofted in the upper atmosphere, and the likelihood of large-amplitude variability. By assuming forsterite as a haze particle, we successfully explain the wavelength-dependent amplitude with submicron-sized haze particle sizes of around 0.4 mu m. W0047 links the earlier spectral and later spectral type brown dwarfs in which rotational modulations have been observed; the large amplitude variations in this object make this a benchmark brown dwarf for the study of cloud properties close to the L/T transition.

Un premier pan de ma thèse concerne deux différents mécanismes de sauvetage du Y par le X. Premièrement, j'ai participé à une controverse sur la compensation de dosage chez les mammifères. Une hypothèse avait été proposée dans les années 60 par Susumo Ohno, proposant un mécanisme de compensation en deux temps. Chez les mâles, la perte de nombreux gènes sur le Y entraîne un déséquilibre de dosage car ces gènes qui étaient précédemment présents en deux copies sont devenus unicopie, soit une division d'expression par deux. Selon l'hypothèse d'Ohno, chez les mammifères en réponse à cela le X aurait doublé son expression, mais dans les deux sexes menant ainsi à une expression trop élevée chez les femelles. Ce deuxième problème de dosage aurait alors été résolu par la mise en place d'une inactivation aléatoire de l'un des deux X chez les femelles. Tandis que la deuxième partie de l'hypothèse d'Ohno, l'inactivation du X, a été très étudiée, la première partie est restée spéculative jusqu'aux années 2000. En étudiant des données d'expression du X humain j'ai pu montrer, de manière concomitante avec d'autres auteurs, que la première partie de l'hypothèse d'Ohno n'est pas totalement vraie car seule une partie des gènes sont sur-exprimés. J'ai ensuite participé à l'écriture d'une revue visant à donner une explication alternative à la compensation de dosage pour l'évolution de l'inactivation du X chez les femelles mammifères. Deuxièmement, j'ai étudié la présence de conversion génique X-Y dans plusieurs gènes, au sein de nombreuses espèces de primates. Mes travaux me mènent à discuter le fait que ce type d'évènement soit effectivement favorisé par la sélection. Je pose l'hypothèse que ces conversions géniques ont été maintenues de manière neutre. Ces deux travaux ne vont pas dans le sens d'un chromosome X sauvant le Y avec beaucoup de zèle. Dans un dernier temps, m'éloignant des espèces modèles, j'ai étudié les chromosomes sexuels particuliers d'une algue brune : Ectocarpus siliculosus. Cela m'a permis de vérifier si le scénario évolutif actuel des chromosomes sexuels est toujours valide dans un groupe d'eucaryotes séparé des animaux depuis plus d'un milliard d'années / The first part of my thesis concerns two different mechanisms of the Y being rescued by the X. Firstly, I contributed to a controversy on mammalian dosage compensation. During the 60s Susumo Ohno hypothesized a two-step dosage compensation mechanism. In males, the high loss of Y-linked genes led to a dosage imbalance: these genes were previously present in two allelic copies and became unicopy, meaning that their expression has been halved. According to Ohno’s hypothesis, in response to this imbalance the mammalian X would have doubled its expression in the two sexes, resulting in a to high expression in females. This second dosage imbalance would have been resolved by the random inactivation of one of the two Xs in females. Whereas the second part of Ohno’s hypothesis, the X-chromosome inactivation, has been well studied, the first part remained speculative until the 2000s. I studied human X-linked expression data and was able to show, concomitantly with other authors, that the first part of Ohno’s hypothesis is not totally true as only some of the X-linked genes are hyperexpressed. I later participated in the writing of a review aiming to give an alternative hypothesis for the evolution of X-chromosome inactivation in mammalian females than dosage compensation. Secondly, I studied signatures of X-Y gene conversion in several genes within numerous primate species. Myresults led me to discuss if these events were indeed selected for. I hypothesize that these gene conversion events occurred in a neutral manner. These two different studies suggest that the X chromosome may not be as much a help for the Y as has been suggested. Lastly, moving away from model species, I studied the peculiar sex chromosomes of a brown alga: Ectocarpus siliculosus. This work allowed me to test if the current hypotheses on sex chromosome evolution still hold in a eukaryotic group that diverged from animals more than one billion years ago

Orientador: Marcos Fernando de Souza Teixeira / Banca: Ana Maria Pires / Banca: Antonio Carlos Dias Angelo / Resumo: A formação de filmes poliméricos contendo azobenzeno tem recebido atenção especial devido à sua aplicação em dispositivos fotônicos. Neste trabalho estudamos a eletropolimerização de Bismarck Brown R (4-3- (2,4-diamin-5-metilfenil)- 4-metilfenildiazenil]diazenil-6-metilbenzeno-1,3-diamindiclorohidrato), filmes ultra-finos sobre substratos de ITO. Foi realizado o estudo do comportamento do filme polimérico variando-se parâmetros durante a etapa de eletropolimerização para a otimização do poliBBR, visando o desenvolvimento de eletrodos modificados para serem utilizados como sensores químicos. O uso da técnica eletroquímica na preparação de filmes poliméricos tem diversas vantagens, tais como a formação do filme diretamente sobre diferentes substratos, controle de espessura do filme, alta reprodutibilidade, geração de polímeros dopados e possibilidade de imobilização de espécies durante a fase de polimerização. Os filmes ultra-finos depositados nos substratos condutores por eletropolimerização foram caracterizados eletroquimicamente (voltametria cíclica e pulso diferencial), espectroscopia de ultravioleta-visível e microscopia de força atômica (AFM). O trabalho se destaca por possuir pouco ou nenhum relato na literatura sobre os dados obtidos dos estudos eletroquímicos e ópticos do comportamento do polímero de Bismarck Brown R. Foram obtidos dados interessantes no comportamento óptico no estudo da imobilização de íons metálicos na estrutura polimérica do BBR, destacando-se as diferentes geometrias e conformações (cis e trans) investigadas no trabalho / Abstract: The formation of azobenzeno containing polymeric films have been special attention due to its application in photonic devices. In this work we studied the electropolymerization of Bismarck Brown R (4-3-(2,4-diamin-5-methylphenyl)-4-methylphenyldiazenyl]diazenyl-6-methilbenzene-1,3-diamindiclorohidrato), ultra thin films on substrates of ITO. Was carried out study the behavior of the polymer film varying the parameters during the step for the electropolymerization polyBBR optimization, in order to develop modified electrodes to be used as chemical sensors. The use of electrochemical technique for preparing polymer films have several advantages, such as film formation directly on different substrates, film thickness control, high reproducibility, generating doped polymers and possible immobilization of species during the polymerization. The ultra-thin films deposited in conductive substrates were characterized electrochemically (cyclic voltammetry and differential pulse), UV-Vis spectroscopy and atomic force microscopy (AFM). The work stands out due to little or no reports in the literature on data obtained from studies of the electrochemical and optical behavior of polymer Bismarck Brown R. We obtained interesting data on optical behavior in the study immobilization of metal ion in the polymeric structure of the BBR, highlighting the different geometries and conformations (cis and trans) investigated in the work / Mestre

O arroz (Oryza sativa L.) é consumido principalmente na forma polida, porém uma alternativa nutricionalmente melhor seria o arroz integral, que contém ao redor de 10% de farelo, rico em micronutrientes e compostos bioativos. Dentre esses destacam-se a vitamina E e &#947;-orizanol, aos quais se atribuem diversos efeitos benéficos à saúde. A literatura descreve vários estudos relacionados à presença desses compostos no arroz integral, porém pouco se sabe a respeito da sua estabilidade com o armazenamento, a parboilização e a cocção caseira. Pelo fato do arroz integral apresentar curta vida de prateleira, uma alternativa para aumentar o prazo para o consumo é o emprego da parboilização. A parboilização, que consiste em um processo hidrotérmico, provoca alterações estruturais no amido do grão e a literatura é controversa no que diz respeito à diminuição da digestibilidade do amido e consequentemente à redução do índice glicêmico (IG). Este trabalho teve como objetivos: avaliar os efeitos da parboilização sobre a disponibilidade do amido por meio da cinética de hidrólise do amido estimando o índice glicêmico (IG) em cultivares de arroz integral com diferentes teores de amilose; analisar o efeito da parboilização, do armazenamento por seis meses e da cocção caseira do arroz integral sobre a estabilidade dos compostos bioativos, e correlacionar os compostos bioativos com a atividade antioxidante do arroz, antes e após o processamento. Foram analisadas 36 amostras pertencentes a diferentes cultivares selecionadas de arroz integral e parboilizado integral das safras de 2007 e 2008 e outras três amostras de arroz integral e parboilizado integral, adquiridas no comércio local da cidade de São Paulo. A partir do índice de hidrólise (IH) in vitro, foi estimado o IG. A vitamina E e o &#947;-orizanol foram extraídos com metanol, separados por CLAE-fase reversa e quantificados por curvas padrão correspondentes. A atividade antioxidante foi avaliada pelos métodos de DPPH&#8226; e ORAC. Foi verificado que a disponibilidade do amido de todas as amostras de arroz foi pouco afetada pela parboilização nas condições empregadas de modo que os IH permaneceram similares aos das amostras não parboilizadas. As amostras com teor intermediário de amilose apresentaram os menores IH (p<0,05). O IG estimado nas amostras cruas e parboilizadas foi cerca de 80%, tanto nas cultivares de arroz selecionadas quanto nas amostras comerciais e não foi observada alteração com o processamento. Com relação aos compostos bioativos, os teores de vitamina E e &#947;-orizanol no arroz integral cru foram, em média de 25 e 188mg/kg, respectivamente. A vitamina E foi sensível ao processo de parboilização, ao armazenamento e à cocção, com perdas de 50% ou mais, em relação à concentração no grão integral in natura. Já o &#947;-orizanol mostrou-se mais estável frente a qualquer tratamento, com perda de no máximo 20% da sua concentração inicial. A maior correlação entre a concentração de compostos bioativos e atividade antioxidante foi encontrada para a vitamina E. / Rice (Oryza sativa L.) is consumed mostly in the milled form. However, due to its content of bran, vitamin E and &#947;-oryzanol, the intake of brown rice has been recommended. Although previous studies ascribed some important health benefits related to these brown rice\'s compounds, information regarding the effect of cooking, storage and parboiling on these substances remains to be elucidated. Rice parboiling is a hydrothermal process consisting of soaking, heating and drying that provide technological and nutritional benefits to the consumer. Until now, if parboiling process decreases the starch digestibility and consequently reduces the glycemic index (GI) is unclear. The objectives of the present study were: to evaluate the effect of the parboiling process on starch digestibility through a GI estimation by the kinetics of starch hydrolysis in rice cultivars with different levels of amylose; to analyze the effect of traditional parboiling, cooking and storage for six months on the stability of bioactive components as well as to correlate the content of bioactive components of rice with its antioxidant activity before and after parboiling. Thirty-six samples of brown rice and parboiled brown rice harvested in 2007 and 2008 were analyzed. In addition, three commercial cultivars of both brown and parboiled brown samples from local market that were obtained in São Paulo were also studied. The glycemic index (IG) was estimated from the hydrolysis index (IH). Vitamin E homologues and &#947;-oryzanol were extracted simultaneously with methanol and analyzed by HPLC-RP/UV and fluorescence detection in a single run. Peak areas were converted to the corresponding by the standards of &#945;- and &#947;-tocopherol, &#945;- and &#947;-tocotrienol and &#947;-oryzanol. The antioxidant capacity was evaluated by both, DPPH&#8226; and ORAC methods. The results indicated that starch digestibility from all rice samples was little affected by parboiling under the conditions employed in the present study. Samples with intermediate amylose content had the lowest HI (p <0.05). The estimated GI in raw and parboiled samples was 80% in all rice cultivars selected and in commercial samples as well. The parboiling showed no effect on GI. The total tocols and &#947;-orizanol contents in raw rice were 25 and 188 mg/kg, respectively. The vitamin E homologues were the most affected by parboiling, storage and cooking than &#947;-oryzanol with a decrease of 50% or more when compared to the raw grain. However, &#947;-oryzanol was more stable during either treatment with 20% loss of when compared to raw rice. The most significant correlation between the concentration of bioactive compounds and antioxidant activity was found for vitamin E.

Tendo em vista a natureza finita dos minerais naturais, torna-se evidente a necessidade de utilizarmos este recurso de maneira estratégica. Desta forma, diversas pesquisas vêm sendo desenvolvidas principalmente nas áreas químicas, metalúrgicas e mineralógicas desde as etapas de extração, beneficiamento, aplicação e reutilização dos resíduos de minérios. Portanto, é extremamente importante a intensificação dos estudos para aumentar o conhecimento quanto às características e propriedades físico-químicas destes minerais, visando melhorar o seu aproveitamento e longevidade das jazidas naturais, como as fontes de bauxita, que é a principal matéria-prima para a produção de óxido de alumínio fundido. Na sua forma cristalina mais comum, denominada coríndon, ou óxido de alumínio ?, sua baixa condutividade elétrica, baixo calor específico, alta condutividade térmica, alto ponto de fusão, elevada dureza e resistência mecânica, o torna adequado para uso em produtos refratários, cerâmicos e abrasivos tais como, lixas, rebolos, ferramentas de corte e de polimento. Na síntese deste produto as principais impurezas que afetam a qualidade dos grãos são Fe, Si, Ca, K, Na e Zr, oriundas da matéria prima bauxita e da carta de mistura, composta por ilmenita, limalha de ferro, carvão vegetal e coque de petróleo. Desta forma, o presente trabalho assumiu o objetivo de estudar a dispersão das propriedades físico-químicas em blocos de alumina fundida marrom obtida em fornos Higgins a arco por eletrofusão, produzidos na Saint-Gobain Abrasivos, unidade de Lorena, SP. Por fim, foram utilizadas técnicas de caracterização físico-químicas de difratometria de raios X (DRX), análises químicas de fluorescência de raios X (FRX), ensaio de dureza Knoop e caracterização microestrutural via (MEV/EDS). Desta forma, foi definido o mapeamento composicional nos blocos de alumina eletrofundida marrom, que servirão como referência técnico-científica para subsidiar ações de melhoria deste produto, em decorrência do avanço do estado da arte deste referido assunto. / The mineral ores are not renewable sources and we need to use it in the best way possible. In this way, a large number of researches are being developed around the world aiming the improvement of current methods of production mainly in chemical, metallurgy, mineralogical from the steps of extraction, processing, application and reuse of waste ore. Therefore, it is extremely important to intensify the studies to increase the knowledge about the characteristics and physicochemical properties of these minerals, in order to improve their utilization and longevity of natural deposits, such as sources of bauxite, which is the main raw material to product aluminum oxide fused. In its most common crystalline form, called corundum or ?-aluminum oxide, its low electrical conductivity, low specific heat, high thermal conductivity, high melting point, high hardness and mechanical strength, making it suitable for use as refractories, ceramics and fine or coarse abrasives. The synthesis of this product major impurities that affect quality of grain is Fe, Si, Ca, K, Na and Zr, derived from the raw material bauxite and the mixture chart consisting of ilmenite, iron filings, charcoal and coke oil. Thus, this shows the dispersion of physicochemical properties of brown fused alumina blocks produced by eletrocfusion at Higgins furnace process in the company Saint Gobain Abrasivos, Lorena- SP. Finally, the samples were physicochemical analyzed by X ray diffraction (XRD), chemical analyses by X ray fluorescence (XRF), hardnes using Knoop method, microstructural characterization by (SEM). The results of this work show a compositional gradient map of the fused alumina block; that shows the main physicochemical differences into the block, to support changes in the alumina production process; and it is also important to improve the actual state of art of this particular theme.

As macroalgas marinhas constituem uma importante fonte de produtos naturais, devido à sua composição química, rica em substâncias fenólicas, terpenos e polissacarídeos sulfatados, apresentando potencial biotecnológico como fonte de substâncias com atividade antioxidante, antiviral, antitumoral e antibacteriana. Nesse sentido, o objetivo do presente estudo foi avaliar o potencial de prospecção de macroalgas do litoral do Espírito Santo (ES), mediante estudos dos potenciais antioxidante e bioativo de extratos brutos de quatro espécies de algas pardas (Chnoospora minima, Dictyopteris plagiogramma, Padina gymnospora e Sargassum cymosum) e de uma espécie de alga verde (Codium isthmocladum). A caracterização inicial dos extratos acetato de etila e metanólico das algas pardas, demonstrou a presença de constituintes com características distintas, indicando que pertencem à diferentes classes fenólicas. Os extratos metanólicos e aquosos das cinco espécies apresentaram os maiores rendimentos, sendo utilizados para análise do potencial antioxidante e bioativo. O extrato metanólico de P. gymnospora apresentou o maior potencial antioxidante e o maior teor de substâncias fenólicas totais pelo ensaio Folin-Ciocalteu, indicando o potencial dessa espécie como ingrediente funcional e na busca de substâncias antioxidantes naturais. As espécies analisadas apresentaram potencial bioativo (antiviral e antitumoral), sendo que os extratos aquosos foram mais ativos, quando comparados aos metanólicos. O maior potencial antiviral foi encontrado nos extratos aquosos de P. gymnospora, S. cymosum e C. isthmocladum, e o maior potencial antitumoral nos extratos aquosos de D. plagiogramma e C. isthmocladum. Tanto o potencial antiviral, como antitumoral podem estar relacionados à presença de substâncias fenólicas e polissacarídeos sulfatados nos extratos. Os resultados obtidos demonstram que as espécies estudadas, principalmente D. plagiogramma, P. gymnospora, S. cymosum e C. isthmocladum, apresentam potencial para prospecção de produtos naturais / Marine macroalgae are an important source of natural products, due to their chemical composition, rich in phenolic substances, terpenes and sulphated polysaccharides, presenting biotechnological potential as a source of substances with antioxidant, antiviral, antitumor and antibacterial activity. In this sense, the objective of the present study was to evaluate the potential of macroalgae prospecting on the coast of Espírito Santo (ES), through studies of the antioxidant and bioactive potentials of crude extracts of four species of brown seaweeds (Chnoospora minima, Dictyopteris plagiogramma, Padina gymnospora and Sargassum cymosum) and a species of green seaweed (Codium isthmocladum). The initial characterization of the ethyl acetate and methanolic extracts of the brown seaweeds, showed the presence of constituents with distinct characteristics, indicating that they belong to the different phenolic classes. The methanolic and aqueous extracts of the five species presented the highest yields, being used for analysis of the antioxidant and bioactive potential. The methanolic extract of P. gymnospora presented the highest antioxidant potential and the highest content of total phenolic substances by the Folin-Ciocalteu assay, indicating the potential of this species as a functional ingredient and the search for natural antioxidant substances. The analyzed species presented bioactive potential (antiviral and antitumor), and the aqueous extracts were more active when compared to methanolic. The highest antiviral potential was found in aqueous extracts of P. gymnospora, S. cymosum and C. isthmocladum, and the highest antitumor potential in aqueous extracts of D. plagiogramma and C. isthmocladum. Both antiviral and antitumoral potential may be related to the presence of phenolic substances and sulfated polysaccharides in the extracts. The results showed that the studied species, especially D. plagiogramma, P. gymnospora, S. cymosum and C. isthmocladum, present potential for the prospection of natural products