Desertification, the deterioration of productive and fertile lands into barren and desolate deserts, usually occurs as a result of deforestation, drought, or improper planting and agriculture. This thesis investigates ways to provide reliefs such as water and shelter in a continuously desertifying landscape (Taklamakan desert, Xinjiang, China) for locals, pilgrims, travelers and expedition caravans. To create diverse experiences in the desert, both temporary and permanent structures are considered in this project to minimize further land degradation. Movements of historical trade routes, oasis towns, and modern population fluctuation are examined to determine strategies and locations for intervention. The progressions of architectural, environmental and cultural decay are revealed in three selected sites: the Kapakaskan Village, the Jafar Sadiq Shrine, and the ancient ruined city of Niya. The design and the primary area of study seek to explain and incorporate passive or low energy building systems, form, cultural community, and technological innovations.

Geckos are famous for the skill of switchable adhesion that they use to stick on various surface while keep their fingers super clean. In the dissertation, a unique mechanism was discovered to explain gecko self-cleaning phenomena. Using atomic force microscopy (AFM), we managed to compare the microparticle-substrate adhesion and the microparticle-seta adhesion with a single seta bonded to the AFM cantilever. A dynamic effect was approved that high pulling-off speed could increase the microparticle-substrate adhesion and thus the self-cleaning appears at high moving speed. Based on the self-cleaning theory, a gecko-inspired N-doped graphene surface with switchable adhesion was achieved, which was designed into a bio-inspired micromanipulator with a success rate over 90%. When electrical bias was applied on this biomimetic surface, the charge concentration induced an electrical double layer (ELD) on the convex surfaces, which attracts polar water molecules to form a water bridge on it, significantly enhancing the adhesion on the wrinkled graphene surface, mimicking the capillary force on beetle feet. Therefore, the bio-inspired adhesive surface can be controlled with speed, electrical bias, humidity and different material surfaces. The water attraction phenomenon on the polarized surface was further tested for the potential application of water collection and evaporation in microsystems.

Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: Water collection systems are used in wet-cooling towers (WCTs) with fill over which water to be cooled flows and in evaporative air-cooled heat exchangers (EACHEs) having deluged tube bundles over which water flows to transfer heat from the tubes. They collect and remove water falling from the bottom of the fill or heat exchanger tube bundle while allowing air to pass with limited flow resistance. There are basically two types of collection systems, categorized as trough and basin systems. Trough systems comprise of multiple, evenly spaced parallel troughs extended in one direction with inclined capture plates to direct water into the troughs. The water collects in the troughs and drains under gravity to a collecting tank or manifold from where it is pumped to the sprayers. In basin systems water falls directly into an open basin under gravity where it is collected and can be pumped to the sprayers. The hybrid (dry/wet) dephlegmator (HDWD) for air-cooled steam condensers, which is being developed at Stellenbosch University as discussed by Heyns (2008), Owen (2013) and Anderson (2014), requires a more effective water collection system with a lower pressure drop than what current designs have to offer. In this thesis, an existing trough system is systematically evaluated by means of various high speed camera and flow experiments to determine its performance characteristics and to find ways to improve its catchment effectiveness. A modification is proposed which increases the effectiveness from approximately 92% to 100 % with a relatively small increase in pressure drop, by adding a small deflector plate and reducing the spacing between adjacent troughs. Experimental data and CFD models are used to determine the performance characteristics of the modified trough system for design purposes. For comparison, various basin system designs are proposed and investigated using CFD, where the baseline model is validated by means of experimental data of rectangular cooling tower inlets by Kröger (2004). Rectangular cooling tower inlets are relevant as they have a similar re-circulating flow pattern to what is seen with the water basin inlets at the vicinity of the inlet wall. The numerical data is correlated to determine empirical relations for the flow performance characteristics. The comparison between the modified trough and the different basin systems yields that the trough system requires significantly less fan and pumping power than basin systems and the costs are also expected to be less. / AFRIKAANSE OPSOMMING: Wateropvangstelsels word gebruik in nat koeltorings en verdamping verkoelers, waar waterdruppels in teen-vloei is met n lugstroom. Die stelsel vang die water wat val op en verwyder dit uit die lugstroom met 'n minimale lugweerstand. Daar is twee wateropvangstelsels wat as volg gekategoriseer word: trog stelsel en wateropvangbak stelsel. 'n Trog stelsel bestaan uit eweredige gespasieerde trôe parallel aan mekaar met 'n skuinsvlak om water in die kanaal op te vang. Water dreineer as gevolg van swaartekrag na 'n opvangs tenk waarvan dit terug gepomp word na die sproeiers. In 'n wateropvangbak stelsel val water direk in die bak en word terug gepomp na die sproeiers. 'n Lugverkoelde kondenserstelsels met 'n hibriede (droog/nat) deflegmator wat huidiglik by die Stellenbosch Universiteit ontwikkel word benodig 'n meer effektiewe wateropvangstelsel met 'n lae drukval. In hierdie tesis word bestaande trog stelsels sistematies geëvalueer deur middel van verskeie toetse met 'n hoë spoed kamera en lugvloei eksperimente om die werkverrigtingskarakteristieke te bepaal en om die opvangsvermoë te verbeter. 'n Verbetering word voorgestel wat die opvangsvermoë verbeter van ongeveer 92 % na 100 % met 'n relatiewe klein verhoging in die drukval deur 'n klein leilem by te voeg en die spasiëring tussen trôe te verminder. Eksperimentele data en BVD (berekeningsvloeidinamika) modelle word gebruik om die werkverrigtingskarakteristieke te bepaal van die nuwe trog stelsel vir ontwerps doeleindes. Die modelle is bekragtig deur gebruik te maak van literatuur van inlaatverlies korrelasies vir reghoekige koeltorings, soos gedoen deur Kröger (2004). Die inlaat van reghoekige koeltorings het soortgelyke vloeipatrone en vloeiwegbreking soos wat by die inlaat van die wateropvangbak stelsel gesien word. Die numeriese data word gebruik om 'n vergelyking vir die vloei karakteristieke te bepaal. 'n Vergelykende studie tussen die nuwe trog stelsel en die wateropvangbak stelsel het bewys dat die trog stelsel noemenswaardig minder waaier drywing en pomp drywing benodig.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A colmeia Langstroth traz em seu modelo original uma tampa interna, localizada imediatamente abaixo da tampa que serviria para auxiliar as abelhas na termoregulaÃÃo do ninho. No Brasil, essa tampa interna foi retirada dos componentes da colmeia sob a alegaÃÃo de que o paÃs à tropical e a tampa interna se tornaria desnecessÃria, sem que estudos tenham sido conduzidos a esse respeito. O presente estudo se propÃs a investigar o papel da tampa interna da colmeia Langstroth na homeostase de colÃnias de abelhas africanizadas Apis mellifera no perÃodo de estiagem no SemiÃrido nordestino. O estudo foi realizado nos meses de outubro e novembro de 2012, no SÃtio CanafÃstula do BixopÃ, Distrito de BixopÃ, municÃpio de Limoeiro do Norte-CE. O experimento constou de 10 colmeias sem tampa interna (T1) e 10 colmeias com tampa interna (T2), nas quais se registraram temperatura e umidade relativa no interior das colmeias, a ventilaÃÃo (intensidade e nÃmero de operÃrias ventilando), coleta de Ãgua (nÃmero de abelhas coletoras por horÃrio, nÃmero de viagens por abelha, intervalo entre as viagens e tempo gasto para coleta), bem como o consumo das reservas de alimento entre as colmeias dos dois tratamentos. Os resultados mostraram que houve diferenÃa significativa (p<0,05) para a temperatura e umidade relativa no interior das colmeias, com as mÃdias diferindo estatisticamente entre T1 (32,08Â0,27ÂC e 53,23Â0,62%) e T2 (31,60Â0,33ÂC e 54,96Â0,75%). Os dados de intensidade de ventilaÃÃo, e o nÃmero de abelhas ventilando nÃo diferiram entre os tratamentos T1 (20,65Â0,77 mm e 0,62Â0,14 abelhas) e T2 (20,27Â0,86 mm e 0,3Â0,06 abelhas). Na coleta de Ãgua, houve diferenÃa estatÃstica nos horÃrios de 11:00, 15:00 e 16:00, nos tratamentos T1 (16,25Â2,05, 18,25Â2,28 e 14,00Â1,35) e T2 (8,25Â1,88, 12,25Â0,62 e 9,75Â0,75), como tambÃm no tempo gasto para a coleta de Ãgua (T1=34,86Â0,56 s e T2=37,64Â0,63 s). O nÃmero de viagens/abelha/dia diferiu nos tratamentos T1 e T2 somente entre os quartis I e II (Q1T1: 11,25Â4,52; Q2 T1: 35,5Â22,22; Q1T2: 4Â1,71; Q2 T2: 25,5Â15,28), para o teste de Man-Whitney. No intervalo entre viagens houve diferenÃa estatÃstica somente nos quartis I, II e IV dos tratamentos T1 (Q1T1: 6Â5,13; Q2 T1: 8Â7,41 e Q4 T1: 97Â23,50 min) e T2 (Q1T2: 5,25Â3,94; Q2 T2: 8Â6,94 e Q4 T2: 272Â82,29 min) para o teste de Man-Whitney. A mÃdia de consumo da reserva de alimento nÃo diferiu entre tratamentos, sendo 177,7Â29,9 g em T1 e 141,8Â13,8 g em T2. Conclui-se que a tampa interna da colmeia Langstroth propicia que as abelhas dessas colmeias consigam melhores condiÃÃes de homeostase interna do ninho desprendendo menor esforÃo que aquelas de colmeias sem tampa interna. / The Langstroth hive has its original model in an inner lid, just below the lid which would serve to assist the bees in the nest thermoregulation. In Brazil, the inner cover was removed from the hive components on the grounds that the country is tropical and the inner cover would become unnecessary, but no study has been done in this direction. The present study aims to investigate the role of the inner cover of the hive Langstroth homeostasis of Africanized bee colonies Apis mellifera in the dry season in the Caatinga in Limoeiro Norte-CearÃ. The survey was conducted in October and November 2012 at the site of CanafÃstula BixopÃ, District BixopÃ, in the city of Limoeiro do Norte, state of CearÃ. The experiment consisted of 10 hives without inner cover (T1) and 10 hives with inner cover (T2), in which he recorded temperature and relative humidity in the hives, ventilation (intensity and number of workers fanning), water harvesting (number of collecting bees by time, number of trips per bee, interval between the journeys and time spent for collection), and the consumption of food reserves from the hives of the two treatments. The results showed a significant difference (p <0.05) for temperature and relative humidity in the hives, with averages differing significantly between T1 (32.08  0,27ÂC and 53.23  0.62%) and T2 (31.60  0,33ÂC and 54.96  0.75%). The intensity data of ventilation, and the number of fanning bees did not differ between T1 (20.65  0.77mm and 0.62  0.14 bees) and T2 (20.27  0.86mm and treatments 0.3  0.06 bees). In collecting water, there was no statistical difference in the times of 11:00, 15:00 and 16:00 in T1 (16.25  2.05, 18.25  2.28 and 14.00  1.35 treatments) and T2 (8.25  1.88, 12.25  0.62 and 9.75  0.75), as well as the time spent collecting water (T1 = 34.86  0.56s and T2 = 37.64  0.63s). The number of trips / bee / day differed between the T1 and T2 only between quartiles I and II (Q1T1: 11.25  4.52; Q2 T1: 35.5  22.22; Q1T2: 4  1.71, Q2 T2: 25.5  15.28), for the Man-Whitney test. In between trips was no statistical difference only in quartiles I, II and IV of T1 treatments (Q1T1: 6  5.13; Q2 T1: 8  7.41 and Q4 T1: 97  23.50 min) and T2 (Q1T2: 5.25  3.94; Q2 T2: 8  6.94 and Q4 T2: 272  82.29 min) for the Man-Whitney test. The average consumption of food supply did not differ between treatments, being in T1 177.7  29.9g and 141.8 3.8g in T2. We conclude that the inner cover of the hive Langstroth provides that these bees hives achieve better conditions of internal homeostasis of the nest giving off less effort than those of hives without inner cover in conditions of the Limoeiro do Norte, CearÃ.

Non-wetting surfaces offer enhanced capabilities over bare metal substrates for condensation with or without phase change. This trait can be utilized to broaden strategies in combating water scarcity in water stressed areas. Slippery lubricant infused surfaces have the ability to shed water droplets with lower nucleation times, taking advantage of more of the limited amount of time available to collect dew and fog than traditional surfaces. However, existing studies focus on short durations with scant information available on the longer-term performance or durability of the materials in application environments. To address this knowledge gap, dew harvesting studies were conducted over a 96 hour period on a lubricant infused surface vis-à-vis regular surface of the same material. Three phases of performance are identified and discussed with regard to the water harvesting potential. The second part of the thesis addresses water condensation under conditions where freezing is a potential issue. Non-wetting surfaces have been shown to be a promising method of limiting the formation of ice from sessile droplets. This study explores the effect of surface roughness on the freeze time of sessile water droplets. Superhydrophobic and hydrophobic, lubricant infused, copper surfaces were created via electrodeposition and chemical etching in conjunction with chemical treatments to achieve non-wetting surfaces of varying surface textures. Freezing characteristics on the surfaces are studied experimentally and, for the first time, computationally, wherein the surface is described using a fractal surface topography. The effect of surface engineering on the freezing dynamics and comparison between the experimental and the computational studies are elucidated. / Master of Science / The use of durable, water repelling surfaces that are also thermally conductive provide an opportunity to help alleviate strain from a growing world crisis, water scarcity. Lubricant infused surfaces shed water from their surface by providing a slippery layer for the droplets to slide on, as opposed to bare metal which water tends to cling to. This behavior makes lubricant infused surfaces attractive as a water harvesting method. However, these surfaces degrade over time and must be maintained to perform at their maximum capability, collecting water for 40 minutes more than a bare surface. This thesis focuses on the performance of these surfaces over a 96-hour operating period to characterize the effect lubricant drainage has on the water collection behavior. Freezing water droplets, commonly referred to as icing, poses concerns for safety and operational ability in industries like renewable energy generation, where icing limits efficiency. Non-wetting surfaces have a unique ability to inherently slow down the phase change of a water droplet to ice due to the lower contact area of droplets resting on the surface. This thesis examines superhydrophobic and lubricant infused surfaces of varying degrees of roughness to explore the effect that the contact angle and different surface structures have on the freezing rate of water on the surface. The experimental results are compared to numerical simulations, which is useful in designing systems that would implement this passive icing mitigation technique.

Fatores ambientais abióticos, como o clima, possuem um efeito profundo sobre a biologia dos organismos e sua distribuição em diferentes habitats. Os insetos, sendo o grupo animal mais abundante do planeta, tem papel importante no entendimento de como as variações climáticas afetam a vida na Terra. Neste estudo, utilizamos as formigas-cortadeiras, da espécie Atta sexdens rubropilosa,, para tratar da importância da umidade na escolha de trilhas de forrageio. As colônias utilizadas foram separadas em dois grupos: um grupo controle, mantido em condições normais de alimentação, e um grupo experimental, alimentado com substrato seco, provocando desidratação da colônia. Os dois grupos foram submetidos a um teste de escolha de trilhas para coleta de água: uma das trilhas foi mantida úmida e a outra mantida seca. As formigas que passaram pelas trilhas, por 24 horas, foram contadas e medidas (estas últimas selecionadas aleatoriamente nas trilhas). Após análise de vídeos, os resultados mostraram que, para o fluxo, houve diferença significativa, tanto entre os grupos quanto entre as trilhas. O fluxo foi sempre maior no grupo experimental, em relação ao controle, e maior na trilha úmida que na trilha seca - sendo assimetricamente maior no grupo experimental. Este resultado demonstra que o estado fisiológico da colônia e das operárias influencia fortemente a saída de forrageadoras e a coleta de água. Além disso, mostra que a escolha da trilha foi influenciada pelo ambiente, com grande preferência das formigas pela trilha úmida. Com relação aos tamanhos, a diferença foi significativa para dois fatores: as formigas nas trilhas do grupo experimental eram, em média, menores do que as formigas do grupo controle. Há relatos de que formigas menores são especializadas em coletar água, o que explica este resultado: no grupo experimental, a dessecação impulsiona as formigas a coletar água de maneira sistemática para reidratação. No grupo experimental, as formigas eram menores na trilha seca do que as da trilha úmida, o que vai contra o esperado se levar em consideração as relações alométricas de perda evaporativa de água. É provável que esse fator esteja ligado ao engajamento na tarefa de coleta de água pelas formigas menores, que é constante nas duas trilhas, dada a necessidade da colônia. Mais estudos, no entanto, são necessários para aprimorar e aprofundar estas questões, especialmente levando em conta a dicotomia entre o comportamento individual e o coletivo / Environmental abiotic factors, such as weather, have a profound impact over the biology of organisms e their distribution on different habitats. Insects, being the most abundant animal group on the planet, play an important role to understand how climatic changes affect life on Earth. In this study, we use leafcutter ants of the species Atta sexdens rubropilosa in order to approach the importance of humidity in the choice of foraging trails. The colonies used were separated in two groups: a control group, kept under normal feeding conditions and an experimental group, fed with dry substrate, which provoked dehydration on the colony. Both groups were submitted to a test of trail choice for water collection: one of the trails was kept humid, while the other was kept dry. Ants that travelled through the trails over 24 hours were counted and measured (in the last case, randomly chosen on the trails). After video analysis, the results show that, regarding to flow, there was a significant difference between groups and between trails. Ants flow were always higher on the experimental group than on the control group, and higher on the humid trail than on the dry trail - being asymmetrically higher on the experimental group. These results show that the physiological state of the colony and the workers strongly influences the exit of foragers and the collection of water. Besides, it shows that trail choice was influenced by the environment, with ants preferring the humid trail. Regarding body size, the difference was significant for two factors: ants on the trails of the experimental group were, on average, smaller than ants from the control group. There are reports that smaller ants are specialized on water collection, which explains that difference: on the experimental group, dehydration pushes ants to collect water systematically for rehydrating. On the experimental group, ants were smaller on the dry trail than the ones on the humid trail, which goes against expected when we consider allometric relations for evaporative water loss. It is likely that this factor is connected to the smaller ant´s engagement to the water collection task, which is constant on both trails due the needs of the colony for water. More studies, however, are necessary to improve and deepen those questions, specially taking onto account the dichotomy between individual and collective behavior

FERNANDES, Nayanny de Sousa. Uso da tampa interna da colmeia Langstroth na manutenção da homeostase em colônias de abelhas africanizadas Apis mellifera durante o período de estiagem no semiárido nordestino. 2013. 67 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Zootecnia, Fortaleza-CE, 2013 / Submitted by Nádja Goes (nmoraissoares@gmail.com) on 2016-08-09T15:04:29Z No. of bitstreams: 1 2013_dis_nsfernandes.pdf: 2903368 bytes, checksum: 038ea0edbe123e3b99de127e8a40e3de (MD5) / Approved for entry into archive by Nádja Goes (nmoraissoares@gmail.com) on 2016-08-09T15:04:42Z (GMT) No. of bitstreams: 1 2013_dis_nsfernandes.pdf: 2903368 bytes, checksum: 038ea0edbe123e3b99de127e8a40e3de (MD5) / Made available in DSpace on 2016-08-09T15:04:42Z (GMT). No. of bitstreams: 1 2013_dis_nsfernandes.pdf: 2903368 bytes, checksum: 038ea0edbe123e3b99de127e8a40e3de (MD5) Previous issue date: 2013 / The Langstroth hive has its original model in an inner lid, just below the lid which would serve to assist the bees in the nest thermoregulation. In Brazil, the inner cover was removed from the hive components on the grounds that the country is tropical and the inner cover would become unnecessary, but no study has been done in this direction. The present study aims to investigate the role of the inner cover of the hive Langstroth homeostasis of Africanized bee colonies Apis mellifera in the dry season in the Caatinga in Limoeiro Norte-Ceará. The survey was conducted in October and November 2012 at the site of Canafístula Bixopá, District Bixopá, in the city of Limoeiro do Norte, state of Ceará. The experiment consisted of 10 hives without inner cover (T1) and 10 hives with inner cover (T2), in which he recorded temperature and relative humidity in the hives, ventilation (intensity and number of workers fanning), water harvesting (number of collecting bees by time, number of trips per bee, interval between the journeys and time spent for collection), and the consumption of food reserves from the hives of the two treatments. The results showed a significant difference (p <0.05) for temperature and relative humidity in the hives, with averages differing significantly between T1 (32.08 ± 0,27ºC and 53.23 ± 0.62%) and T2 (31.60 ± 0,33ºC and 54.96 ± 0.75%). The intensity data of ventilation, and the number of fanning bees did not differ between T1 (20.65 ± 0.77mm and 0.62 ± 0.14 bees) and T2 (20.27 ± 0.86mm and treatments 0.3 ± 0.06 bees). In collecting water, there was no statistical difference in the times of 11:00, 15:00 and 16:00 in T1 (16.25 ± 2.05, 18.25 ± 2.28 and 14.00 ± 1.35 treatments) and T2 (8.25 ± 1.88, 12.25 ± 0.62 and 9.75 ± 0.75), as well as the time spent collecting water (T1 = 34.86 ± 0.56s and T2 = 37.64 ± 0.63s). The number of trips / bee / day differed between the T1 and T2 only between quartiles I and II (Q1T1: 11.25 ± 4.52; Q2 T1: 35.5 ± 22.22; Q1T2: 4 ± 1.71, Q2 T2: 25.5 ± 15.28), for the Man-Whitney test. In between trips was no statistical difference only in quartiles I, II and IV of T1 treatments (Q1T1: 6 ± 5.13; Q2 T1: 8 ± 7.41 and Q4 T1: 97 ± 23.50 min) and T2 (Q1T2: 5.25 ± 3.94; Q2 T2: 8 ± 6.94 and Q4 T2: 272 ± 82.29 min) for the Man-Whitney test. The average consumption of food supply did not differ between treatments, being in T1 177.7 ± 29.9g and 141.8± 3.8g in T2. We conclude that the inner cover of the hive Langstroth provides that these bees hives achieve better conditions of internal homeostasis of the nest giving off less effort than those of hives without inner cover in conditions of the Limoeiro do Norte, Ceará. / A colmeia Langstroth traz em seu modelo original uma tampa interna, localizada imediatamente abaixo da tampa que serviria para auxiliar as abelhas na termoregulação do ninho. No Brasil, essa tampa interna foi retirada dos componentes da colmeia sob a alegação de que o país é tropical e a tampa interna se tornaria desnecessária, sem que estudos tenham sido conduzidos a esse respeito. O presente estudo se propôs a investigar o papel da tampa interna da colmeia Langstroth na homeostase de colônias de abelhas africanizadas Apis mellifera no período de estiagem no Semiárido nordestino. O estudo foi realizado nos meses de outubro e novembro de 2012, no Sítio Canafístula do Bixopá, Distrito de Bixopá, município de Limoeiro do Norte-CE. O experimento constou de 10 colmeias sem tampa interna (T1) e 10 colmeias com tampa interna (T2), nas quais se registraram temperatura e umidade relativa no interior das colmeias, a ventilação (intensidade e número de operárias ventilando), coleta de água (número de abelhas coletoras por horário, número de viagens por abelha, intervalo entre as viagens e tempo gasto para coleta), bem como o consumo das reservas de alimento entre as colmeias dos dois tratamentos. Os resultados mostraram que houve diferença significativa (p<0,05) para a temperatura e umidade relativa no interior das colmeias, com as médias diferindo estatisticamente entre T1 (32,08±0,27ºC e 53,23±0,62%) e T2 (31,60±0,33ºC e 54,96±0,75%). Os dados de intensidade de ventilação, e o número de abelhas ventilando não diferiram entre os tratamentos T1 (20,65±0,77 mm e 0,62±0,14 abelhas) e T2 (20,27±0,86 mm e 0,3±0,06 abelhas). Na coleta de água, houve diferença estatística nos horários de 11:00, 15:00 e 16:00, nos tratamentos T1 (16,25±2,05, 18,25±2,28 e 14,00±1,35) e T2 (8,25±1,88, 12,25±0,62 e 9,75±0,75), como também no tempo gasto para a coleta de água (T1=34,86±0,56 s e T2=37,64±0,63 s). O número de viagens/abelha/dia diferiu nos tratamentos T1 e T2 somente entre os quartis I e II (Q1T1: 11,25±4,52; Q2 T1: 35,5±22,22; Q1T2: 4±1,71; Q2 T2: 25,5±15,28), para o teste de Man-Whitney. No intervalo entre viagens houve diferença estatística somente nos quartis I, II e IV dos tratamentos T1 (Q1T1: 6±5,13; Q2 T1: 8±7,41 e Q4 T1: 97±23,50 min) e T2 (Q1T2: 5,25±3,94; Q2 T2: 8±6,94 e Q4 T2: 272±82,29 min) para o teste de Man-Whitney. A média de consumo da reserva de alimento não diferiu entre tratamentos, sendo 177,7±29,9 g em T1 e 141,8±13,8 g em T2. Conclui-se que a tampa interna da colmeia Langstroth propicia que as abelhas dessas colmeias consigam melhores condições de homeostase interna do ninho desprendendo menor esforço que aquelas de colmeias sem tampa interna.

Fatores ambientais abióticos, como o clima, possuem um efeito profundo sobre a biologia dos organismos e sua distribuição em diferentes habitats. Os insetos, sendo o grupo animal mais abundante do planeta, tem papel importante no entendimento de como as variações climáticas afetam a vida na Terra. Neste estudo, utilizamos as formigas-cortadeiras, da espécie Atta sexdens rubropilosa,, para tratar da importância da umidade na escolha de trilhas de forrageio. As colônias utilizadas foram separadas em dois grupos: um grupo controle, mantido em condições normais de alimentação, e um grupo experimental, alimentado com substrato seco, provocando desidratação da colônia. Os dois grupos foram submetidos a um teste de escolha de trilhas para coleta de água: uma das trilhas foi mantida úmida e a outra mantida seca. As formigas que passaram pelas trilhas, por 24 horas, foram contadas e medidas (estas últimas selecionadas aleatoriamente nas trilhas). Após análise de vídeos, os resultados mostraram que, para o fluxo, houve diferença significativa, tanto entre os grupos quanto entre as trilhas. O fluxo foi sempre maior no grupo experimental, em relação ao controle, e maior na trilha úmida que na trilha seca - sendo assimetricamente maior no grupo experimental. Este resultado demonstra que o estado fisiológico da colônia e das operárias influencia fortemente a saída de forrageadoras e a coleta de água. Além disso, mostra que a escolha da trilha foi influenciada pelo ambiente, com grande preferência das formigas pela trilha úmida. Com relação aos tamanhos, a diferença foi significativa para dois fatores: as formigas nas trilhas do grupo experimental eram, em média, menores do que as formigas do grupo controle. Há relatos de que formigas menores são especializadas em coletar água, o que explica este resultado: no grupo experimental, a dessecação impulsiona as formigas a coletar água de maneira sistemática para reidratação. No grupo experimental, as formigas eram menores na trilha seca do que as da trilha úmida, o que vai contra o esperado se levar em consideração as relações alométricas de perda evaporativa de água. É provável que esse fator esteja ligado ao engajamento na tarefa de coleta de água pelas formigas menores, que é constante nas duas trilhas, dada a necessidade da colônia. Mais estudos, no entanto, são necessários para aprimorar e aprofundar estas questões, especialmente levando em conta a dicotomia entre o comportamento individual e o coletivo / Environmental abiotic factors, such as weather, have a profound impact over the biology of organisms e their distribution on different habitats. Insects, being the most abundant animal group on the planet, play an important role to understand how climatic changes affect life on Earth. In this study, we use leafcutter ants of the species Atta sexdens rubropilosa in order to approach the importance of humidity in the choice of foraging trails. The colonies used were separated in two groups: a control group, kept under normal feeding conditions and an experimental group, fed with dry substrate, which provoked dehydration on the colony. Both groups were submitted to a test of trail choice for water collection: one of the trails was kept humid, while the other was kept dry. Ants that travelled through the trails over 24 hours were counted and measured (in the last case, randomly chosen on the trails). After video analysis, the results show that, regarding to flow, there was a significant difference between groups and between trails. Ants flow were always higher on the experimental group than on the control group, and higher on the humid trail than on the dry trail - being asymmetrically higher on the experimental group. These results show that the physiological state of the colony and the workers strongly influences the exit of foragers and the collection of water. Besides, it shows that trail choice was influenced by the environment, with ants preferring the humid trail. Regarding body size, the difference was significant for two factors: ants on the trails of the experimental group were, on average, smaller than ants from the control group. There are reports that smaller ants are specialized on water collection, which explains that difference: on the experimental group, dehydration pushes ants to collect water systematically for rehydrating. On the experimental group, ants were smaller on the dry trail than the ones on the humid trail, which goes against expected when we consider allometric relations for evaporative water loss. It is likely that this factor is connected to the smaller ant´s engagement to the water collection task, which is constant on both trails due the needs of the colony for water. More studies, however, are necessary to improve and deepen those questions, specially taking onto account the dichotomy between individual and collective behavior

Magister Economicae - MEcon / In this thesis, I explore the allocation and use of water for productive and domestic purposes in the village of Siyandhani in the Klein Letaba sub-area, and how the allocation and use is being affected by new water resource management and water services provision legislation and policies in the context of water reform. This problem is worth studying because access to water for domestic and productive purposes is a critical dimension of poverty alleviation.The study focuses in particular on the extent to which policy objectives of greater equity in resource allocation and poverty alleviation are being achieved at local level with the following specific objectives: to establish water resources availability in Letaba/Shingwedzi sub-region, specifically surface and groundwater and examine water uses by different sectors (e.g. agriculture, industry, domestic, forestry etc.,); to explore the dynamics of existing formal and informal institutions for water resources management and water services provision and the relationship between and among them; to investigate the practice of allocation and use of domestic water; to investigate the practice of allocation and use of irrigation water.The study concludes that there is a problem of water scarcity in the study area and that the water scarcity is caused by the growth in the population, specifically in the Giyani area; these problems are exacerbated by financial and institutional obstacles within local institutions of governance. The water scarcity is not, therefore, natural but anthropogenic in nature.The water scarcity is not felt by all sectors, however: some farmers have access to water for irrigation, while many others face great challenges in their farming activities.Overall, people in Siyandhani and surrounding villages surrounding villages in the Letaba Catchment do not have access to water because of human action, hence the use of the concept of manufactured scarcity. The lack of access to water, it is argued,leads to the violation of the human right to water. This study concludes that water reform, which is widely seen as a priority for South Africa, has not yet reached the villages of the Klein Letaba.

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