The objective of this study was to synthesize and characterize new energetic polycyclic "cage" compounds. As part of a program involved in the synthesis of new polynitropolycyclic compounds, 2,6-dinitro-5-methoxy- 7-carbomethoxypentacyclo[5. 3 .0 . 0* • * . CP • i ° . 0* •8]decane has been synthesized. This is a model system which can be used to study (1) the effect of nitro substitution on the photolability of carbon-carbon double bonds and (2) to develop methods for avoiding Haller-Bauer cleavage in cage /3-keto esters when synthesizing polynitro-substituted cage compounds.

Tin electrodeposits produced from aqueous electrolytes are frequently used within the electronics industry due to their high solderability and corrosion protection. One limitation to using these deposits is their spontaneous formation of long conductive filament whiskers. These whiskers grow post-electrodeposition and increase the risk of unwanted electrical shorts within electronic devices. In this thesis, tin electrodeposits produced from a proprietary bright acid Tinmac electrolyte, currently used in industry, were studied. Electrodeposits were produced using a range of current densities with and without agitation and were characterised with respect to crystallographic orientation, topography and surface finish. Moreover, the intermetallic compound (IMC) growth produced at the copper substrate-tin coating interface was assessed over a period of time as its growth is considered to be a significant driving force behind whisker formation. In addition, a technique for the electrochemical anodic oxidation of tin electrodeposits on copper substrates was developed. This technique was used throughout this project for the study of IMC growth from tin electrodeposits as it was able to effectively remove the tin whilst leaving the IMCs and substrate unaffected. Ionic liquids exhibit promising electrochemical characteristics for electrodeposition but are still not widely utilised in industry. Their ability to deposit tin coatings has been studied in the present investigation. Trials concentrated on process optimisation to produce uniform electrodeposits by varying current density, SnCl2.2H2O concentration, and electrolyte composition. These deposits were then characterised and compared to tin coatings of similar thickness produced from Tinmac with respect to topography, surface finish, crystallographic orientation, IMC growth, and whisker propensity. Electrodeposits produced from the ionic liquid electrolyte exhibited a different crystallographic texture, topography, and IMC growth compared to those produced from Tinmac. Moreover, the deposit produced from the ionic liquid featured increased whisker growth compared to those produced from Tinmac, but in a wider context, far less growth than conventional tin electrodeposits in the literature. In addition, by exploiting other electrochemical characteristics of ionic liquids, such as their large potential window, future work may be able to produce novel tin or tin alloy electrodeposits which may further reduce the whisker propensity of deposits produced in this investigation.

This thesis uses laboratory experiments to develop a methodology to estimate the expected welfare benefits of insurance for individuals, conditional on their risk preferences. This methodology is then applied to study the welfare effects of issues that impact microinsurance, or insurance for the poor. The first result is that insurance take-up not a good proxy for the expected welfare gain of an individual’s choice to purchase or not to purchase insurance. The second result is that basis risk reduces the welfare obtained from index insurance. This welfare is significantly improved by having greater behavioral consistency with the Reduction of Compound Lotteries axiom. Finally, the risk of contract non-performance from the insurer significantly reduces the welfare obtained from insurance purchase decisions.

Dentro de los procesos de formación de palabras, el mecanismo morfológico de la composición ha sido poco estudiado en el aimara y en otras lenguas andinas. Esta investigación muestra una descripción de las maneras de cómo se conforman las palabras compuestas en la gramática del aimara de Conima. Por tanto, en este trabajo se analizan la estructura y la combinatoria sintáctica de las palabras compuestas en esta variedad lingüística. La data ha sido recogida de los hablantes y de la información procedente de los principales diccionarios en aimara. En este estudio, se concluye que el aimara de Conima forma compuestos a partir de seis patrones sintácticos que siguen la estructura complemento-núcleo. Finalmente, en relación con su tipología, en la indagación se indica que esta variedad emplea la composición para formar palabras compuestas básicamente de orden nominal. / Within the processes of word formation, the morphological mechanism of the compounding has been little studied in Aymara and other Andean languages. This survey shows a description of the ways in which the compound words are formed in the grammar of Conima Aymara. Therefore, this work analyzes the structure and the syntactic combination of the composition in this linguistic variety. The data has been collected from the speakers and from the main dictionaries in Aymara. The present investigation concludes that the Conima Aymara forms compounds from six syntactic patterns that follow the complement-core structure. Finally, in relation to its typology, this survey points out that the Conima Aymara basically creates nominal compounding. / Revisón por pares

Thesis advisor: Amir H. Hoveyda / Chapter 1. We have developed a single-vessel catalytic protocol for double protoboryl additions to terminal alkynes with B2(pin)2 promoted by Cu complex derived from chiral N-heterocyclic carbene (NHC), to achieve enantiomerically enriched versatile vicinal diborons. Since an alkenyl(pinacolato)boron, which was in situ generated by the first protoboration of a terminal alkyne, can serve as an effective substrate for the second protoboration (alkenylboron can allow delocalization of π electrons of olefin to a partially vacant p orbital on boron), single-vessel catalytic process with 2 equiv. of B2(pin)2 in the presence of sulfonate-bearing chiral NHC–Cu complex, affords enantiomerically enriched 1,2-diborons in up to 93% yield and 97.5:2.5 enantiomeric ratio (e.r.). Site-selective Pd-catalyzed cross-coupling with alkenyl bromide shows the versatility of the resulting diboron compounds, which delivers the coupling product efficiently. Interestingly, only the less hindered, primary C–B bond on vicinal diboron compound participates in the cross coupling. Chapter 2. Cu-catalyzed protocol for selective formation of α-alkenylborons has been demonstrated. With achiral NHC–Cu complex, readily prepared from commercially available imidazolinium salt, various terminal alkynes are converted to internal alkenylborons in up to 93% yield with high to exclusive α selectivity. Propargyl ethers, amides and aryl alkynes are proved to be suitable substrates. Utility of α-alkenylborons is demonstrated by conversion to methyl ketone and synthesis of cyclic alkenylboron compound. In addition, when Cu complex bearing a stronger electron-donating NHC is used, the site selectivity of protoboration reaction becomes reversed, which delivers the alternative isomer, β-alkenylboron efficiently. By altering the steric and electronic nature of NHC, site selectivity is dramatically changed. Mechanistic basis for site selectivity is presented. Chapter 3. Efficient and selective protocol for synthesis of enantiomerically enriched silylborons is described. In the presence of achiral NHC–Cu complex, site- and stereoselective protosilyl additions to terminal alkynes afford a wide range of alkyl- and aryl-substituted (E)-β-alkenylsilanes. Chiral monodentate NHC−Cu complex promotes enantioselective protoboration of alkyl- or alkenyl-bearing alkenylsilanes, delivering vicinal borosilanes with up to 96.5:3.5 e.r. When an alkene bearing both silyl and aryl groups is utilized, on the other hand, geminal silylboron is obtained with high enantio- (93:7–98.5:1.5 e.r.) and site selectivity (up to >98% geminal). In this case, we have reasoned that the electronic attribute of aryl unit is more dominant than the silyl group to control site selectivity. To demonstrate the utility of the Cu-catalyzed transformation, we have illustrated the formal synthesis of bruguierol A, natural product active against Gram-positive and also Gram-negative bacteria. The key intermediate geminal borosilane is provided by sequential NHC–Cu-catalyzed protosilylation and protoboration of terminal alkyne in 77% overall yield with 97.5:2.5 e.r. and 97% site selectivity. Additionally, stereochemical models to account for levels and trends in site- and enantioselectivity are proposed. Chapter 4. New methods for enantioselective protonation of 2-B(pin)-bearing allylcopper, which is in situ generated by site-selective Cu–B addition to 1,1-disubstituted allene, are presented. Transformations are promoted by a chiral NHC–Cu complex, affording an alkenylboron containing α-carbon stereogenic center. Enantiomerically enriched aryl-, heteroaryl- and silyl-bearing alkenylborons are generated in high yield (up to 98%) and selectivities (up to >98% site selectivity and 96.5:3.5 e.r.). To explore the utility of enantiomerically enriched alkenylborons, we have developed Cu-catalyzed enantioselective allylic alkenyl addition to allylic phosphate. A chiral NHC–Cu complex promotes the allylic substitution of enantiomerically enriched alkenylboronic acid with ally phosphate to deliver 1,4-diene in 62% yield with 96:4 d.r. (>98% stereoselectivity). Chapter 5. We have developed a single-vessel, multicomponent process to synthesize N-bearing quaternary carbon stereogenic centers with exceptional diastereo- (>98:2 d.r. for all cases) and high enantioselectivity (88:12 to >99:1 e.r. except one case). Especially, protecting group-free ketoimine (“N–H” ketoimine), which can be prepared by alkylation of a readily available nitrile, has been utilized for the study. The transformation of “N–H” ketoimine is very useful because the obtained amine has no protecting group, which allows us to avoid the deprotection step as well as to be able to choose appropriate protecting group for subsequent chemical reactions. By oxidation of α-tertiary carbamine with NaBO3, β-amino ketones (Mannich reaction product) are obtained in up to 83% yield. A stereochemical model to account for the level of diastereo- and enantioselectivity are presented using DFT calculations. To show the utility of the present method, we have synthesized a medicinally active compound, which was studied for Alzheimer’s disease. The Cu-catalyzed protocol delivers the core structure of the target molecule with exclusive diastereo- and enantioselectivity (>98:2 d.r. and 99.5:0.5 e.r.). / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

O objetivo deste trabalho foi investigar o comportamento fisiológico e bioquímico de plantas de citros (Citrus spp.) submetidas à aplicação do herbicida glyphosate. Para tanto, foram realizados quatro estudos. No primeiro, avaliou-se o efeito de glyphosate (doses entre 0 e 720 g e.a.ha-1, aplicadas sobre a parte aérea das plantas) nas concentrações foliares de chiquimato, aminoácidos livres totais e fenóis e na fotossíntese de plantas de citros em condições controladas. Foram testadas mudas de limão ‘Cravo’ (Citrus limonia L. Osbeck), com 4 meses de idade, e mudas de ‘Valência’ (Citrus sinensis L. Osbeck) sobre ‘Swingle’ (Poncirus trifoliata (L.) Raf x Citrus paradisi Macf), com 24 meses de idade. No segundo estudo avaliou-se, em condições de campo, a toxicidade de glyphosate em plantas submetidas à aplicação atingindo o caule (doses entre 0 e 2160 g e.a.ha-1) ou toda a parte aérea (doses entre 0 e 720 g e.a.ha-1). Os materiais vegetais testados foram plantas de laranja ‘Valência’ sobre ‘Swingle’ e limão ‘Cravo’, com 20 e 27 meses de idade, respectivamente. No terceiro avaliou-se a queda de frutos de laranjeira ‘Pera’ (Citrus sinensis L. Osbeck) em função do glyphosate. No último estudo investigou-se a possibilidade de aplicação acidental simulada de glyphosate causar intoxicação e queda de frutos em plantas de laranja ‘Pera’. No primeiro estudo verificou-se efeito de glyphosate somente nas concentrações de chiquimato e aminoácidos livres totais das mudas de limão ‘Cravo’; porém, os efeitos foram transitórios. Não houve efeito nos conteúdos de fenóis e clorofila total e na atividade fotossintética. Não se constatou qualquer efeito nas características bioquímicas e na fotossíntese das mudas de ‘Valência’, indicando significativa tolerância ao herbicida. No estudo a campo, as plantas de citros atingidas pelo glyphosate no caule não sofreram intoxicação. Apenas a aplicação nas doses de 360 e 720 g e.a.ha-1 sobre a parte aérea afetou as plantas. O principal sintoma de intoxicação consistiu na emissão de brotações deformadas, indicando efeito nas regiões meristemáticas. Os efeitos nas folhas pré-formadas foram pequenos ou inexistentes. Todas as plantas atingidas pelo herbicida se recuperaram entre seis e doze meses após a aplicação. Nos estudos para avaliar a queda de frutos observou-se que o glyphosate promove a produção de etileno, causando a queda destes quando estão em fase final de maturação. A queda ocorreu principalmente devido ao contato direto com a pulverização e não devido à translocação do herbicida. No último estudo, constatou-se que a aplicação acidental simulada foi parcialmente interceptada pelo mato, não causando efeito significativo na queda de frutos e no desenvolvimento vegetativo das plantas de citros. / The objective of this research was to evaluate physiological and biochemical responses of citrus (Citrus spp.) plants sprayed with the herbicide glyphosate. Four studies were done to attain this objective. By the first one, it were investigated the effects of glyphosate (dosages from 0 to 720 g a.e.ha-1 applied on plants canopies) on the leaf contents of shikimate, total free amino acids and phenolic compounds, and on photosynthesis of citrus plants under controlled conditions. The experiments were conducted using ‘Rangpur Lime’ (Citrus limonia L. Osbeck) rootstock, with 4 months old, and ‘Valencia’ (Citrus sinensis L. Osbeck) scion grafted on ‘Swingle’ (Poncirus trifoliata (L.) Raf x Citrus paradisi Macf) rootstock, with 24 months old. By the second trial, it was evaluated, under field conditions, the toxicity of glyphosate on citrus plants sprayed directly to the the trunk (dosages from 0 to 2160 g a.e.ha-1) or on the canopy (dosages from 0 to 720 g a.e.ha-1). The plants tested were ‘Valencia’ var. grafted on ‘Swingle’ var. and on ‘Rangpur Lime’ var., with 20 and 27 months old, respectively. By the third trial, it was evaluated the fruit dropping of ‘Pera’ var. (Citrus sinensis L. Osbeck) in relation to glyphosate spray. The last trial was conducted to evaluate if an accidental simulated spray of glyphosate can cause toxicity and fruit dropping in ‘Pera’ citrus var. The results by the first study showed effects of glyphosate only on shikimate and total free amino acids contents of ‘Rangpur Lime’ seedlings. However, these effects were temporaries. No effect was found on phenolic compound contents and on the photosynthetic characteristics evaluated. It was not postrayed any effect on biochemical and photosynthetic characteristics of the ‘Valencia’ plants, indicating significant glyphosate tolerance. By the second study, the citrus plants sprayed with glyphosate on their trunks have not showed intoxication. Only the application of glyphosate at dosages of 360 and 720 g a.i.ha-1 on the canopies affected the plants. The main toxic symptoms consisted of deformation of new flushes, indicating effect on plant meristems. The effects of glyphosate were low or none in the mature leaves. All plants sprayed by glyphosate have been recovered by from six to twelve months after the application. In the study, in order to evaluate the fruit dropping, it was found that the herbicide glyphosate induced ethylene production, causing fruit dropping when they are in final phase of ripening. Fruit dropping occurred mainly due to the direct contact of the spraying instead of the herbicide translocation. By the last study it was found that the accidental simulated spraying is partially intercepted by weeds, do not causing significant effect on fruit dropping and citrus growth.

O Parque Estadual Turístico do Alto Ribeira - PETAR - localizado no vale do Ribeira de Iguape, a 315 km de São Paulo, é uma das últimas áreas de mata Atlântica preservada e com uma diversidade enorme de fauna e flora. Por se tratar de uma região bastante complexa do ponto de vista ambiental, vários são os conflitos existentes no que se refere ao planejamento do uso e ocupação do solo, dado que a região apresenta quase 40% de seu território bloqueado por força do que dispõem as legislações ambientais que, a partir da década de 80, criaram várias unidades de conservação ambiental. No entanto, cerca de 30% da área ocupada do PETAR é utilizada para atividades impróprias à preservação desse patrimônio público. Essas atividades são representadas basicamente por: agricultura, exploração mineral, descarga de esgoto doméstico não tratado e expansão populacional. A utilização de compostos organoclorados na agricultura e exploração intensa de metais durante anos na região têm contaminado o ecossistema. Desta forma, o objetivo deste trabalho foi estabelecer uma metodologia para avaliar a qualidade ambiental do solo e sedimento da região do PETAR. Considerando-se as características econômicas da região - agricultura, mineração e ecoturismo - o solo e sedimento foram analisados com respeito a compostos organoclorados e metais pesados. Os metais avaliados foram o chumbo, devido aos problemas com a mineração e, em adição, cádmio, cobre, zinco, níquel, cromo, alumínio, manganês e ferro, sendo estes analisados por absorção atômica. Foram avaliados os compostos organoclorados lindano, HCB e os PCBs. Para suas determinações foi utilizado um cromatógrafo a gás com detector de captura de elétrons. Os resultados mostram que, de modo geral, a região do PETAR encontra-se impactada por Pb, Zn e Cu, principalmente nos sedimentos, com alto grau de contaminação. Foram também encontradas concentrações de compostos organoclorados acima do valores permissíveis. / The Parque Estadual Turístico do Alto Ribeira - PETAR - located in the Vale do Ribeira de Iguape, distant 315 km from São Paulo, is one of the last preserved areas of Atlantic forest. It has an enormous diversity of fauna and flora. This is a region with a great complexity under the environmental point of view, so there are lot of conflicts referring to the land usage and occupation planning, once the region presents almost 40% of its territory blocked by force of what environmental legislation dispose, which since the 80’s decade, have created several environmental conservation units. However, about 30% of the PETAR occupied area are used for activities that are unsuitable to the preservation of this common wealth. These activities are represented basically by agriculture, mineral exploration, discharge of non treated domestic sewage and population expansion. The usage of organochlorine compounds in agriculture and intensive metal exploration in the region during years contaminated the ecosystem. In this way, the purpose of this work was to establish a methodology to evaluate the environment quality of the soil and sediment from PETAR region. Considering the economic characteristics of the region - agriculture, mining and ecotourism - the soil and sediment had been analyzed with respect to organochloride compounds and heavy metals. The evaluated metals had been lead, due to the problems with the mining and, in addition, cadmium, copper, zinc, nickel, chromium, aluminium, manganese and iron, having these been analyzed by atomic absorption. The organochloride compounds HCH, HCB and the PCBs had been evaluated. For its determination a gas chromatograph with electron capture detector was used. The result shows that, in a general way, the PETAR region find impacted by Pb, Zn and Cu, mainly in the sediments, with high contamination intensity. Organochloride compound concentrations also had been found above the permissible values.

Neste trabalho, investigou-se a elaboração mecânica do composto intermetálico TiFe por moagem de bolas com alta energia. Uma forte aderência do material moído, particularmente nas paredes do recipiente de moagem, foi o principal problema verificado com tempos de moagem superiores a 1 hora (moinho agitador). Tentativas para resolver este problema foram realizadas inicialmente com o emprego de agentes controladores de processo (ACPs), como etanol, ácido esteárico, polietileno de baixa densidade, benzeno e ciclohexano, em diferentes quantidades (1 a 20% em massa) e tempos (1 a 40 h), mantendo-se constantes outros parâmetros de moagem como a razão bola:pó em massa (10:1) e o tamanho das bolas (=7mm). Os rendimentos mais elevados (em termos da massa de pó não aderido) foram obtidos quando se utilizaram grandes quantidades de benzeno e ciclohexano (101 e 103% em massa, respectivamente), porém com a formação de TiC ao invés de TiFe em razão da decomposição do ACP e reação do carbono com as partículas de titânio. As moagens foram realizadas posteriormente sem o emprego de qualquer ACP e também utilizando um moinho planetário. Várias estratégias foram investigadas para se tentar mitigar a aderência incluindo-se: (a) moagem de uma pequena quantidade da mistura de pós de Ti e de Fe, revestindo as paredes do recipiente e as bolas de moagem, antes da moagem da carga principal, (b) moagem pausada com aberturas intermediarias do recipiente em atmosfera ambiente, (c) moagem pausada para rotação e inversão da posição do recipiente de moagem (apenas no moinho agitador), (d) moagem isolada dos pós de Ti e de Fe, antes da moagem da mistura, e (e) moagem do pó de Fe com o Ti hidretado. Os melhores resultados, em termos de diminuição da aderência combinada com a formação majoritária do composto TiFe durante a moagem, foram obtidos quando se adotou o procedimento de inversão/rotação, juntamente com o processo de revestimento preliminar do recipiente e das bolas de moagem (26% em massa). Rendimentos maiores foram obtidos com a utilização do TiH2 no moinho planetário, porém sem a formação majoritária do TiFe durante a moagem. / In this work an investigation on the mechanical alloying of the intermetallic compound TiFe by high-energy ball milling was conducted. Strong adherence of milled material, particularly at the vial walls, was seen to be the main problem at milling times higher than 1 hour (shaker mill), hindering the compound synthesis. Attempts to prevent this problem were accomplished first by adding different process control agents (PCAs), like ethanol, stearic acid, low density polyethylene, benzene and cyclohexane at variable quantities (1 to 20 wt. %) and times (1 to 40 h), keeping constant other milling parameters like ball to powder mass ratio (10:1) and balls size (=7mm). Highest yields (related to the non adhered powder) were attained with larger amounts of benzene and cyclohexane (101 and 103 wt. %, respectively), but with TiC formation during milling instead of TiFe due to the PCA decomposition and the reaction of the carbon with and titanium particles. Milling was conducted further without adding any PCA and also using a planetary ball mill. Several strategies were tried to avoid or minimize the adherence including: (a) milling of a small quantity of the Ti and Fe powder mixture, dirtying the vial walls and the balls surfaces before milling the main charge, (b) stepwise milling with intermediate openings of the vial in air, (c) stepwise milling with the rotation and the inversion of the vial position between the steps (only in the shaker mill), (d) milling Ti and Fe powders (apart from each other) before milling the mixture of them, and (e) milling Fe powder with Ti hydride powder. Best results concerning both yield and major TiFe formation during milling were verified with the rotation/inversion procedure combined with preliminar dirtying of the vial and balls (26 wt.% in the shaker mill). Higher yields could be attained by using TiH2 powder in the planetary mill, but with no major TiFe formation during milling.

O primeiro capítulo desta dissertação é dedicado a uma revisão teórica da interação dos raios-X com cristais e métodos utilizados para a determinação de estruturas cristalinas. Nos capítulos seguintes, descreve-se os equipamentos experimentais utilizados e resolução de duas estruturas cristalinas cujos principais resultados são apresentados a seguir: Estrutura do complexo HO(ReO4)34 TDTD 3 H2O. Sistema cristalino; monoclínico; grupo espacial P21/c; a=17.955(3) Å b=17.100(6) Å c=12.570(3) Å &#946=92.48(2) ° V=3855(3) ޵ z=4; Dc = 2.720 g/cm3; (MoK&#945)= 0.71073 Å &#181=114.08 cm-1. O índice de discordância final foi de R = 6.4% para 3050 reflexões com I >3&#963(I). O cátion HO+3 é coordenado por oito átomos de oxigênio, que configuram um dodecaedro (simetrias D2d). Os poliedros de coordenação são ligados por grupos TDTD, dando origem a cadeias infinitas na direção a. Estrutura de Ormosalin - C14H16O6. Sistema cristalino: monoclínico, grupo espacial: P21/c; a=10.765(4) Å b=14.692(5) Å c=8.374(4); &#946=98.02(3)° V=1305(2) &#1973, z=4, Dc = 1.43 g/cm3, &#955(MoK&#945)=0.71073 &#197, &#191=0.07 mm-1; R=0.058 para 807 reflexões com estrutura conta com dois anéis de cinco membros em conformação torcida antissimétrica / In the first chapter of this work we review some theoretical aspects concerning the interaction of X-rays with crystals and the methods used to determine crystal structure. The following chapters describe the experimental equipments used and the determination of two crystalline structures. The main results obtained are now out11ned. The structure of the complex HO(ReO4)34 TDTD 3 H2O. Crystal system, monoclinic, space P21/c; a=17.955(3) Å b=17.100(6) Å c=12.570(3) Å &#946=92.48(2) ° V=3855(3) ޵ z=4; Dc = 2.720 g/cm3; (MoK&#945)= 0.71073 Å &#181=114.08 cm-1. The final R factor was 6.4 % for 3050 ref1eetions with I&#88053&#963(I). The cation HO+3 is coordinated by eight oxygen atoms which have a dodecahedron configuration (symme - try D2d). The coordination polyhedrons are linked together by a TDTD group that coordinates two neighbouring cations HO+3, giving rise to an infinite chain along the crystallographic a direction. The structure of Orrnosalin C14H16O6. Crystal system, monoclinic; space group P21/c; a=10.765(4) Å b=14.692(5) Å c=8.374(4); &#946=98.02(3)° V=1305(2) &#1973, z=4, Dc = 1.43 g/cm3, &#955(MoK&#945)=0.71073 &#197, &#191=0.07 mm-1; R=0.058 for 807 reflections with I&#88053&#963(I). The structure consists of two five membered rings forming a anti - symmetric twisted conformation

As abelhas utilizam sinais visuais e olfatórios para encontrar plantas das quais utilizam recursos florais. Algumas abelhas adquiriram hábitos crepuscular ou noturno e forrageiam durante períodos de pouca luminosidade. Algumas espécies de abelhas noturnas são conhecidas por possuírem adaptações morfológicas do sistema visual que lhes permitem o voo noturno, e assim facilitam o encontro de plantas que podem ser utilizadas como recursos. No presente estudo investigamos se espécies crepusculares Megalopta sodalis, Megommation insigne e Ptiloglossa latecalcarata, que utilizam Campomanesia phaea como recurso, e possuem adaptações na morfologia externa do sistema visual. A hipótese principal é que seriam encontrados olhos compostos, omatídeos e ocelos maiores, assim como menor quantidade de omatídeos nos olhos compostos quando comparadas às abelhas diurnas. Para tanto, medimos o comprimento, área e número de omatídeos dos olhos compostos, assim como o diâmetro dos omatídeos e ocelos. A distância intertegular foi medida para ter um controle do tamanho corporal. Além das abelhas crepusculares acima citadas, utilizamos as abelhas diurnas Bombus brasiliensis, Bombus morio, Melipona bicolor e Euglossa cordata para comparação. Para a medida dos olhos fizemos um molde de esmalte e a partir deste obtivemos imagens que foram analisadas utilizando-se o software ImageJ e Matlab. Para as outras medidas, foram obtidas imagens em estereomicroscopio que foram analizadas com o ImageJ. Utilizamos a análise estatística de permutação para ver se havia diferença entre as abelhas crepusculares e diurnas, e correlação de Spearman para ver se a medida estava correlacionada à distância intertegular. Foi realizado um levantamento das espécies com registro de interação com abelhas crepusculares e noturnas e de suas características florais com uma respectiva análise descritiva. As abelhas crepusculares deste estudo possuem o diâmetro dos ocelos e omatídeos maiores e olhos compostos com maior comprimento e área, e menor número de omatídeos. Algumas variáveis estão correlacionadas com a distância intertegular. As flores visitadas por abelhas noturnas possuem em sua maioria cores claras, perfume acentuado e são odoríferas. As abelhas crepusculares deste estudo possuem adaptações na morfologia externa, o que lhes permite o voo no período de pouca luminosidade. Algumas espécies de abelhas que forrageiam em período de pouca luminosidade visitaram flores de cores fortes e uma não odorífera, isso pode estar relacionado à capacidade de reconhecer cores em ambientes pouco iluminados. Algumas espécies de abelhas forrageiam durante o dia e a noite, essa plasticidade do comportamento pode ser um caminho pelo qual caracteres vantajosos para esse ambiente sejam selecionados. Para as plantas, ter as abelhas noturnas como polinizadoras pode ser vantojoso. Então plantas que possuem sinais reconhecidos pelas abelhas noturnas podem se beneficiar com a polinização noturna, evitando o disperdício de pólen com as abelhas diurnas. A maioria das abelhas foi generalista na utlilização do recurso, mas parece haver preferência por certas espécies de plantas / The bees use visual cues and olfactory to find plants which own floral resources. Some bees acquired crepuscular or nocturnal habits and foraging during periods of low light. Some nocturnal bees species are recognized to possess morphological adaptations of the visual system that enable them to practice the night flight, and thus facilitate the matching of plants that can be used as resources. In the present study we investigated whether crepuscular species Megalopta sodalis, Megommation insigne e Ptiloglossa latecalcarata, using Campomanesia phaea as a resource, have adaptations in the external morphology of the visual system. The main hypothesis was that the eyes were composed of ommatidia and larger ocelli as well as lower amount of ommatidia in the compound eyes when compared to daytime bees. Therefore, we measure the length, the area and number of ommatidia of the compound eye and also the diameter of the ommatidia, ocelli, and intertegular distance to have a control of body size. In addition to the crepuscular bees mentioned above, we used the diurnal bees Bombus brasiliensis, Bombus morio, Euglossa cordata, and Melipona bicolor for comparison. For the measurement of eyes, we made a nail polish mold and from this mold was obtained images which were analyzed using ImageJ and Matlab software. For other measures, we obtained images in stereomicroscope that were analyzed only using ImageJ. We use the statistical analysis of permutation to observe if there was any difference between the crepuscular and diurnal bees, and Spearman correlation to see if the measure was correlated with distance intertegular. In addition, we conducted a survey of species interaction with record crepuscular and nocturnal bees and their floral characteristics with a descriptive analisys. The crepuscular bees in this research have lager diameter of omatidea and ocelli, and larger area and length of compound eyes, and less number of omatidea per eye. Most of the flowers visited by nocturnal bees have pale color, scent and nocturnal anthesis. Some bee species that forage in low light visit flowers with strong color, and one bee visited flower without scent, this can be related with capacibility to recoginized colors in environments with low light. Some bees forage during day and night, this phenotypic plasticity of behavior can be a way that advantageous characters for this environment are selected. For plants can be advantageous. Then plants that posses sinals recognized by nocturnal and crepuscular bees can be benefited through nocturnal pollination, avoiding daylight bees waste their polen. The most of bees were generalists in their utilization of flower resource but seems to have preference for some plant species