Cyclic sieving for two families of non-crossing graphs

We prove the cyclic sieving phenomenon for non-crossing forests and non-crossing graphs. More precisely, the cyclic group acts on these graphs naturally by rotation and we show that the orbit structure of this action is encoded by certain polynomials. Our results confirm two conjectures of Alan Guo

Cyclic sieving phenomenon in non-crossing connected graphs

We prove an instance of the cyclic sieving phenomenon in non-crossing connected graphs, as conjectured by S.-P. Eu.Comment: 13 pages, 5 figure

Palaeoclimate characteristics in interior Siberia of MIS 6–2: first insights from the Batagay permafrost mega-thaw slump in the Yana Highlands

Syngenetic permafrost deposits formed extensively on and around the arising Beringian subcontinent during the Late Pleistocene sea level lowstands. Syngenetic deposition implies that all material, both mineral and organic, freezes parallel to sedimentation and remains frozen until degradation of the permafrost. Permafrost is therefore a unique archive of Late Pleistocene palaeoclimate. Most studied permafrost outcrops are situated in the coastal lowlands of northeastern Siberia; inland sections are, however, scarcely available. Here, we describe the stratigraphical, cryolithological, and geochronological characteristics of a permafrost sequence near Batagay in the Siberian Yana Highlands, the interior of the Sakha Republic (Yakutia), Russia, with focus on the Late Pleistocene Yedoma ice complex (YIC). The recently formed Batagay mega-thaw slump exposes permafrost deposits to a depth of up to 80 m and gives insight into a climate record close to Verkhoyansk, which has the most severe continental climate in the Northern Hemi- sphere. Geochronological dating (optically stimulated luminescence, OSL, and 14C ages) and stratigraphic implications delivered a temporal frame from the Middle Pleistocene to the Holocene for our sedimentological interpretations and also revealed interruptions in the deposition. The sequence of lithological units indicates a succession of several distinct climate phases: a Middle Pleistocene ice complex indicates cold stage climate. Then, ice wedge growth stopped due to highly increased sedimentation rates and eventually a rise in temperature. Full interglacial climate conditions existed during accumulation of an organic-rich layer – plant macrofossils reflected open forest vegetation existing under dry conditions during Marine Isotope Stage (MIS) 5e. The Late Pleistocene YIC (MIS 4–MIS 2) suggests severe cold-stage climate conditions. No alas deposits, potentially indicating thermokarst processes, were detected at the site. A detailed comparison of the permafrost deposits exposed in the Batagay thaw slump with well-studied permafrost sequences,both coastal and inland, is made to highlight common features and differences in their formation processes and palaeo-climatic histories. Fluvial and lacustrine influence is tem-orarily common in the majority of permafrost exposures, but has to be excluded for the Batagay sequence. We interpret the characteristics of permafrost deposits at this location as a result of various climatically induced processes that are partly seasonally controlled. Nival deposition might have been dominant during winter time, whereas proluvial and aeolian deposition could have prevailed during the snowmelt period and the dry summer season

Efeitos da queima prescrita nos microrganismos do solo

Fire is an integral part of nature, but it has come to assume the role of threat, in particular, due to the frequency and scale that wildfires have acquired in recent years. Prescribed burning can be a fire prevention tool because it removes vegetable fuel in excess. However, it is necessary to know the effects of its application to understand how it affects natural ecosystems, including the soil. The main objective of this work is to evaluate the effects of prescribed burnings on high mountain soil microorganisms, simultaneously evaluating changes in the chemical and physical properties of the soil. The study area is located in Asín de Broto, in the Central Pyrenees, Spain. To develop this study, samples were collected from three different depths (0-1, 1-2, and 2-3 cm) and at 16 different points: 4 points never burned (UB), 4 points immediately after a prescribed burning (B0), 4 points where a prescribed burning was performed 5 years ago (B5) and 4 points where a prescribed burning was performed 9 years ago (B9). For the determination of densities and porosity, a single sample was collected at each of the 16 points, with a depth between 0 and 6 cm. No significant changes in soil moisture were observed at any depth over the years. In the B0 samples, significant increases were observed in porosity, pH, and electrical conductivity, between 0 and 1 cm, and structural stability, pH, organic matter content, and electrical conductivity at depths between 1 and 3 cm. In samples B5, the structural stability decreased between 0 and 2 cm, but remained similar to the values before fire from 2 to 3 cm; pH remained higher at all depths; the organic matter content decreased between 0 and 1 cm, but remained higher between 1 and 3 cm; electrical conductivity returned to pre-burning values at all depths. In samples B9, structural stability returned to pre-fire values between 0 and 2 cm, but decreased between 2 and 3 cm; pH remained high at all depths; the organic matter content returned to pre-fire values between 0 and 1 cm, but maintained high values at other depths; electrical conductivity remained similar to pre-fire values at all depths. In the biological properties, in samples B0, a decrease in CFU of bacteria between 0 and 1 cm was observed, but without significant changes between 1 and 2 cm; there was an increase in fungal CFU between 0 and 2 cm. In samples B5, there was an increase in bacterial CFU between 0 and 1 cm, but a decrease between 1 and 2 cm; in fungi, there was a decrease between 0 and 1 cm, but the number of CFU remained similar between 1 and 2 cm. It was concluded that prescribed burning does not significantly affect most physical and chemical properties of the soil and may even have positive effects on some properties, even after nine years. However, the microorganism communities are severely affected and do not recover at the end of this period.O fogo é uma parte integrante da natureza, mas que tem vindo a assumir o papel de ameaça, em particular pela frequência e pelas dimensões que os incêndios adquiriram nos últimos anos. A queima prescrita pode ser uma ferramenta de prevenção contra os incêndios porque remove o excesso de combustível vegetal. No entanto, é necessário conhecer os efeitos da sua aplicação para entender como afeta os ecossistemas naturais, entre os quais o solo. O principal objetivo deste trabalho consiste na avaliação dos efeitos das queimas prescritas sobre os microrganismos do solo de alta montanha, avaliando simultaneamente alterações nas propriedades químicas e físicas do solo. A área de estudo está localizada em Asín de Broto, nos Pirinéus Centrais, em Espanha. Para desenvolver este estudo foram recolhidas amostras de três profundidades diferentes (0-1, 1-2 e 2-3 cm) e em 16 pontos distintos: 4 pontos nunca queimados (UB), 4 pontos imediatamente após uma queima (B0), 4 pontos em que uma queima foi realizada há 5 anos (B5) e 4 pontos em que uma queima foi realizada há 9 anos (B9). Para a determinação das densidades e da porosidade, foi recolhida uma única amostra em cada um dos 16 pontos, com uma profundidade entre 0 e 6 cm. Não foram observadas alterações significativas na humidade do solo em nenhuma das profundidades ao longo dos anos. Nas amostras B0, foram observados aumentos significativos na porosidade, no pH e na condutividade elétrica, entre 0 e 1 cm, e na estabilidade estrutural, no pH, no teor de matéria orgânica e na condutividade elétrica a profundidades entre 1 e 3 cm. Nas amostras B5, a estabilidade estrutural diminuiu entre 0 e 2 cm, mas manteve-se semelhante aos valores antes do fogo dos 2 aos 3 cm; o pH manteve-se mais alto a todas as profundidades; o teor de matéria orgânica diminuiu entre 0 e 1 cm, mas manteve-se mais alto entre 1 e 3 cm; a condutividade elétrica voltou aos valores anteriores à queima a todas as profundidades. Nas amostras B9, a estabilidade estrutural voltou aos valores antes do fogo entre 0 e 2 cm, mas diminui entre 2 e 3 cm; o pH continuou alto a todas as profundidades; o teor de matéria orgânica voltou aos valores antes do fogo entre 0 e 1 cm, mas manteve os valores elevados nas outras profundidades; a condutividade elétrica manteve-se semelhante aos valores antes do fogo a todas as profundidades. Nas propriedades biológicas, nas amostras B0, foi observada uma diminuição das UFC de bactérias entre 0 e 1 cm, mas sem alterações significativas entre 1 e 2 cm; houve um aumento de UFC de fungos entre 0 e 2 cm. Nas amostras B5, houve aumento de UFC de bactérias entre 0 e 1 cm, mas uma diminuição entre 1 e 2 cm; nos fungos, ocorreu uma diminuição entre 0 e 1 cm, mas o número de UFC manteve-se semelhante entre 1 e 2 cm. Concluiu-se que a queima prescrita não afeta significativamente a maioria das propriedades físicas e químicas do solo e pode até ter efeitos positivos em algumas propriedades, mesmo ao fim de nove anos. No entanto, as comunidades de microrganismos são severamente afetadas e não recuperam ao fim deste período.Mestrado em Engenharia do Ambient

Touching Impermanence: Experiential Embodied Engagements with Materiality in Contemporary Art Practice

Touching impermanence describes the experiential moment in an art encounter when one senses the enchanted reality of one’s interconnections within the sentient matterflow of existence. All matter in existence is constantly vibrating, changing, assembling and evolving into forms and organisms, cycling through decay and disintegration, then reforming again with diversity and difference; this is the impermanence of sentient matter-flow. Humans are just one form of these reciprocal assemblages; we are within and part of sentient matter-flow. We also co-create with sentient matter-flow, changing these cycles on micro and macro levels, just as they change us. On a macro level human actions have impacted and changed the Earth’s biosphere, altering and polluting sentient matter-flows to the extent that our present time period is becoming known as the Anthropocene, the human age of destruction and disconnection. There are many efforts to readdress our anthropocentric feelings of apathetic disconnection from the Earth; one is found in the arts and correlates with my practice-led research. This doctoral study of sensate experiences of materiality and haptic thinking, which provide both maker and audience with direct palpable experience of time, forms a specific understanding of touching impermanence. My art processes involve working with tactile materials such as beeswax; tree branches, stumps and bark; paper; ash; rocks; ice; snow; charcoal; light and fungi. Engaging with these materials cocreatively involves a methodology of touch, multisensorily following materialities’ sentient matter-flow. Acting with the material, I am present to the material’s own sense of time, interactions, agency, histories, layers of interbeing and interconnections with surrounding matter. This requires being open to the mysteriousness of materials, inviting moments of enchantment within art encounters and the realisation of touching impermanence. This thesis investigates my studio practice and works produced, alongside related practices of Australian and international artists, by drawing on the intersections between New Materialism discourses and Buddhist philosophy to address aspects of phenomenology and eco-philosophy in the complexities of these art practices and artwork encounters

Forest, fire and monsoon: A palaeo-environmental assessment of the ecological threshold dynamics of South-east Asia’s dry forests

Projections that the frequency and intensity of extremes in the Asian monsoon will rise are being made with increasing confidence. There is concern that these events may drive south-east Asian dry tropical forest (SASDTF) - an extensive ecoregion affected by this climate system - across critical thresholds. This could have implications both in terms of biodiversity loss from an area of global ecological significance, and for the flow of services that it provides to a populous part of the world. Little work has been done on the threshold dynamics of SASDTF, however, research from dry tropical forests elsewhere indicates that associated ecosystems may be susceptible to abrupt reorganisation to savanna under reduced precipitation regimes, increased rainfall seasonality, or if burnt. This project uses a high-resolution, multi-proxy analysis of two sediment cores extracted from Cambodian crater lakes - situated at the heart of SASDTF - to assess long-term ecological response to these identified drivers. Reconstruction of past climate using geochemical proxies of lake water levels indicates a stepwise weakening of the summer monsoon from 4700 to 450 cal. yrs BP. This trend is punctuated by a notable dry period from 1900 to 1500 cal. yrs BP. Charcoal records demonstrate that fire has been a persistent feature of SASDTF over the past 4700 years. A reconstruction of the ecological history of SASDTF indicates resilience to climatic forcing and periods of high fire activity. As vegetation appears to shift from closed to open forest formations during a weaker summer monsoon or in response to fire activity, the mosaics of open- and closed- units that characterise the ecoregion have been identified as important for future forest persistence. Broadly, this research emphasises the limitations of generalist biome-scale resilience modelling, stressing the importance of long-term, intra-biome level research for predicting ecological response to climatic and anthropogenic forcing