Hf-Nd Isotopic Variability in Mineral Dust from Chinese and Mongolian Deserts: Implications for Sources and Dispersal

Mineral dust provenances are closely related to the orogenic processes which may have distinct Hf-Nd isotopic signatures. Here we report the clay-sized (\u3c2 μm) Hf-Nd isotope data from Asian dust sources to better constrain the source and transport dynamics of dust deposition in the North Pacific. Our results show that there is a more positive radiogenic Hf isotopic composition with clay-sized fractions than the corresponding bulk sample and a decoupling of the Hf-Nd couplets in the clay formation during the weathering process. The clay-sized Hf-Nd isotopic compositions of the desert samples from the Sino-Korean-Tarim Craton (SKTC) are different from those of the Gobi and deserts from the Central Asian Orogeny Belt (CAOB) due to varying tectonic and weathering controls. The Hf-Nd isotopic compositions of dust in the North Pacific central province (NPC) match closely with those from the Taklimakan, Badain Jaran and adjacent Tengger deserts, implying that the NPC dust was mainly transported from these potential sources by the westerly jet. Our study indicates that dusts from the CAOB Gobi deserts either didn\u27t arrive in NPC or were quantitatively insignificant, but they were likely transported to the North Pacific margin province (NPM) by East Asian winter monsoon

Contrastive Energy Prediction for Exact Energy-Guided Diffusion Sampling in Offline Reinforcement Learning

Guided sampling is a vital approach for applying diffusion models in real-world tasks that embeds human-defined guidance during the sampling procedure. This paper considers a general setting where the guidance is defined by an (unnormalized) energy function. The main challenge for this setting is that the intermediate guidance during the diffusion sampling procedure, which is jointly defined by the sampling distribution and the energy function, is unknown and is hard to estimate. To address this challenge, we propose an exact formulation of the intermediate guidance as well as a novel training objective named contrastive energy prediction (CEP) to learn the exact guidance. Our method is guaranteed to converge to the exact guidance under unlimited model capacity and data samples, while previous methods can not. We demonstrate the effectiveness of our method by applying it to offline reinforcement learning (RL). Extensive experiments on D4RL benchmarks demonstrate that our method outperforms existing state-of-the-art algorithms. We also provide some examples of applying CEP for image synthesis to demonstrate the scalability of CEP on high-dimensional data.Comment: Accepted at ICML 202

A constant Chinese Loess Plateau dust source since the late Miocene

© 2019 The Authors The Pliocene-Pleistocene boundary marks a major change in global climate and East Asian monsoon dynamic. However, the role of the global atmospheric dust-cycle over this time is unclear; in particular the degree to which changes in the dust cycle influenced climate change, were driven by climate change, and how these processes interacted. Chinese loess records past dust-cycle history and the influences of aridification and monsoon circulation over the last 40 Ma. Previous work on the Chinese Loess Plateau argue over whether changes in dust source occur at the Pliocene-Pleistocene boundary, or at 1.2 Ma, despite these intervals marking major shifts in monsoon dynamics. We present Sr, Nd and Hf isotope data from multiple sites and show that dust source largely remains unchanged across these boundaries. Shifts in geochemistry are due to changes in grain-size and weathering. While the transport pathway (river, deserts, direct aeolian) is unclear, these tracer isotopes show that dust was dominantly sourced from the Northern Tibetan Plateau, with some input from the local bedrock. This shows that a major established and constant dust source on the Tibetan Plateau has been active and unchanged since late Miocene, despite dramatically changing climate conditions. Changes in loess accumulation are a function of climate change in Tibetan Plateau source regions rather than effects from increased aridification over the Pliocene-Pleistocene boundary

Late Quaternary aggradation and incision in the headwaters of the Yangtze River, eastern Tibetan Plateau, China

River aggradation or incision at different spatial-temporal scales are governed by tectonics, climate change, and surface processes which all adjust the ratio of sediment load to transport capacity of a channel. But how the river responds to differential tectonic and extreme climate events in a catchment is still poorly understood. Here, we address this issue by reconstructing the distribution, ages, and sedimentary process of fluvial terraces in a tectonically active area and monsoonal environment in the headwaters of the Yangtze River in the eastern Tibetan Plateau, China. Field observations, topographic analyses, and optically stimulated luminescence dating reveal a remarkable fluvial aggradation, followed by terrace formations at elevations of 55-62 m (T7), 42-46 m (T6), 38 m (T5), 22-36 m (T4), 18 m (T3), 12-16 m (T2), and 2-6 m (T1) above the present floodplain. Gravelly fluvial accumulation more than 62 m thick has been dated prior to 24-19 ka. It is regarded as a response to cold climate during the last glacial maximum. Subsequently, the strong monsoon precipitation contributed to cycles of rapid incision and lateral erosion, expressed as cut-in-fill terraces. The correlation of terraces suggests that specific tectonic activity controls the spatial scale and geomorphic characteristics of the terraces, while climate fluctuations determine the valley filling, river incision and terrace formation. Debris and colluvial sediments are frequently interbedded in fluvial sediment sequences, illustrating the episodic, short-timescale blocking of the channel ca. 20 ka. This indicates the potential impact of extreme events on geomorphic evolution in rugged terrain

O Serviço Social nas Autarquias e a sua Importância para o Desenvolvimento Social Local

Aprofundar o conhecimento do Serviço Social e reflectir sobre a prática profissional do Assistente Social e a criação de políticas sociais com vista ao desenvolvimento social local, nomeadamente, na Câmara Municipal da Batalha, constituíram o objectivo de estudo. A descentralização do Poder Central para o Poder Local, assente na proximidade ao cidadão, mantém-se em discussão na agenda política e ganha maior relevo na conjuntura actual, com a reforma do Poder Local. Contudo, até ao momento, as transferências no âmbito da Acção Social mantêm-se bastante genéricas e sem regulamentação. Por essa razão, o Poder Local intervém na área social sem que essas competências estejam delineadas pela tutela e muitas vezes sem o devido financiamento, deixando aos Executivos Municipais a decisão sobre a criação de políticas sociais. Neste sentido, com o intuito de assegurarem os interesses das suas populações, as Câmaras Municipais implementam medidas sociais de âmbito local, que se revelam mais ou menos intensas, consoante o importância que lhes é dada por cada Executivo, que define as áreas de intervenção prioritárias e quais os recursos disponíveis para investir no domínio social. O Serviço Social revela ser um importante recurso das autarquias na criação das políticas sociais locais, na medida em que o Assistente Social, ao conhecer o território e intervir mais próximo dos cidadãos, pode propor programas de desenvolvimento local, adequados aos interesses da população. No caso particular da Câmara Municipal da Batalha, reflectiu-se sobre a prática da Assistente Social e evocaram-se as políticas sociais por esta planeadas e desenvolvidas, revelando o seu contributo para o desenvolvimento social do concelho. Atestou-se, em género de conclusão, que, apesar do Assistente Social ter um papel cada vez mais preponderante na execução das políticas de desenvolvimento local, a sua prática profissional tem limitações por não ser capaz, por si só, de resolver problemas sociais de génese estrutural, influenciados pela conjuntura nacional e internacional

Smartphone sensing meets transport data: A collaborative framework for transportation service analytics

National Research Foundation (NRF) Singapore under International Research Centres in Singapore Funding Initiativ

Late Quaternary paleoclimatic and geomorphological evolution at the interface between the Menyuan basin and the Qilian Mountains, northeastern Tibetan Plateau

The Tibetan Plateau is regarded as an amplifier and driver of environmental change in adjacent regions because of its extent and high altitude. However, reliable age control for paleoenvironmental information on the plateau is limited. OSL appears to be a valid method to constrain the age of deposits of glacial and fluvial origin, soils and periglacial structures in the Menyuan basin on the northeastern Tibetan Plateau. Dating results show glaciers advanced extensively to the foot of the Qilian mountains at ~. 21. ka, in agreement with the timing of the global Last Glacial Maximum (LGM) recorded in Northern Hemisphere ice cores. Comparison with results from the eastern Tibetan Plateau suggests that the factor controlling glacial advance in both regions was decreased temperature, not monsoon-related precipitation increase. The areas of the Menyuan basin occupied by glacio-fluvial deposits experienced continuous permafrost during the LGM, indicated by large cryoturbation features, interpreted to indicate that the mean annual temperature was ≥. 7. °C lower than at present. Glacio-fluvial systems in the Menyuan basin aggraded and terraces formed during cold periods (penultimate glaciation, LGM, and possibly the Younger Dryas) as a response to increased glacial sediment production and meltwater runoff then. © 2013 University of Washington