Context label learning: improving background class representations in semantic segmentation

Background samples provide key contextual information for segmenting regions of interest (ROIs). However, they always cover a diverse set of structures, causing difficulties for the segmentation model to learn good decision boundaries with high sensitivity and precision. The issue concerns the highly heterogeneous nature of the background class, resulting in multi-modal distributions. Empirically, we find that neural networks trained with heterogeneous background struggle to map the corresponding contextual samples to compact clusters in feature space. As a result, the distribution over background logit activations may shift across the decision boundary, leading to systematic over-segmentation across different datasets and tasks. In this study, we propose context label learning (CoLab) to improve the context representations by decomposing the background class into several subclasses. Specifically, we train an auxiliary network as a task generator, along with the primary segmentation model, to automatically generate context labels that positively affect the ROI segmentation accuracy. Extensive experiments are conducted on several challenging segmentation tasks and datasets. The results demonstrate that CoLab can guide the segmentation model to map the logits of background samples away from the decision boundary, resulting in significantly improved segmentation accuracy. Code is available

Causality-inspired single-source domain generalization for medical image segmentation

Deep learning models usually suffer from the domain shift issue, where models trained on one source domain do not generalize well to other unseen domains. In this work, we investigate the single-source domain generalization problem: training a deep network that is robust to unseen domains, under the condition that training data are only available from one source domain, which is common in medical imaging applications. We tackle this problem in the context of cross-domain medical image segmentation. In this scenario, domain shifts are mainly caused by different acquisition processes. We propose a simple causality-inspired data augmentation approach to expose a segmentation model to synthesized domain-shifted training examples. Specifically, 1) to make the deep model robust to discrepancies in image intensities and textures, we employ a family of randomly-weighted shallow networks. They augment training images using diverse appearance transformations. 2) Further we show that spurious correlations among objects in an image are detrimental to domain robustness. These correlations might be taken by the network as domain-specific clues for making predictions, and they may break on unseen domains. We remove these spurious correlations via causal intervention. This is achieved by resampling the appearances of potentially correlated objects independently. The proposed approach is validated on three cross-domain segmentation scenarios: cross-modality (CT-MRI) abdominal image segmentation, cross-sequence (bSSFP-LGE) cardiac MRI segmentation, and cross-site prostate MRI segmentation. The proposed approach yields consistent performance gains compared with competitive methods when tested on unseen domains

Enforcing trustworthy cloud SLA with witnesses: A game theory–based model using smart contracts

There lacks trust between the cloud customer and provider to enforce traditional cloud SLA (Service Level Agreement) where the blockchain technique seems a promising solution. However, current explorations still face challenges to prove that the off-chain SLO (Service Level Objective) violations really happen before recorded into the on-chain transactions. In this paper, a witness model is proposed implemented with smart contracts to solve this trust issue. The introduced role, “Witness”, gains rewards as an incentive for performing the SLO violation report, and the payoff function is carefully designed in a way that the witness has to tell the truth, for maximizing the rewards. This fact that the witness has to be honest is analyzed and proved using the Nash Equilibrium principle of game theory. For ensuring the chosen witnesses are random and independent, an unbiased selection algorithm is proposed to avoid possible collusions. An auditing mechanism is also introduced to detect potential malicious witnesses. Specifically, we define three types of malicious behaviors and propose quantitative indicators to audit and detect these behaviors. Moreover, experimental studies based on Ethereum blockchain demonstrate the proposed model is feasible, and indicate that the performance, ie, transaction fee, of each interface follows the design expectations

Evolution of tourism in a flagship protected area of China

Nature-based tourism in protected areas, which is growing worldwide, offers much potential to enhance biodiversity conservation, poverty alleviation, and ultimately sustainable development. Understanding the evolution of protected areas as tourism destinations and the causes and consequences of changing supply and demand elements is an essential step toward sustainably managing tourism in these critical ecosystems. This research applied the Tourism Area Life Cycle (TALC) model to illustrate and analyze the 30-year evolution of tourism in Wolong Nature Reserve. Being inscribed in UNESCO Biosphere Reserve and World Heritage programmes, Wolong is a flagship protected area in China. We showed that the Reserve experienced exploration, involvement, and development stages of the TALC before tourism growth was completely halted by the Wenchuan Earthquake in 2008. We systematically investigated the changes related to the evolution of tourism and identified various internal and external driving forces. We examined the dynamics of politics, economy, and tourism growth that might propel the Reserve through the life cycle and identified significant tourism governance structural changes through the stages. The results have implications for sustainable tourism development in China's protected areas and also contribute to a broader and general understanding of the complex relationships between protected areas, sustainable tourism, and community development

Dynamic carbon and sulfur cycling in the aftermath of the Lomagundi-Jatuli Event: Evidence from the Paleoproterozoic Hutuo Supergroup, North China Craton

The unprecedented positive δ13C excursion in carbonates deposited between 2.2 and 2.0 Ga, known as the Lomagundi-Jatuli Event (LJE), has been documented globally and linked to the rise of atmospheric oxygen. Increasing oxidation inevitably changed the atmosphere-hydrosphere system, but few chemostratigraphic or quantitative constraints for the aftermath of this event exists. Here, we describe a ~200 m-thick carbonate succession in the Huaiyincun Formation, Hutuo Supergroup, ~2.0–1.9 Ga, from the North China Craton. There is a lithological transition from pink-purple dolostones to grey dolostones at ca. 91.6 m above the base of the Huaiyincun Formation. The former are more enriched in hematite and detrital minerals, whereas the latter contain more organic matter but almost no detrital phases. Meanwhile, the frequent occurrence of tempesite structures, along with the abrupt decline of stromatolites in the upper Huaiyincun Formation, suggest a storm-dominated environment. These distinct features within the Huaiyincun Formation reveal increased water depth during a transgression event. Two types of Raman spectra of organic matter were found in the lower and upper Huaiyincun Formation, respectively, which is proposed to be the result of variable oxidation. At 65.6 m, 26 m below the lithological transition (~91.6 m), remarkable decreases in both δ13Ccarb and δ34SCAS are observed. This discordance between C-S isotopic excursions and sedimentological and mineralogical variations argues against a seawater depth gradient effect of the δ13Ccarb and δ34SCAS curves. Instead, the decline of δ13Ccarb rather correlates with the negative δ13Ccarb excursions in ca. 2.0 Ga carbonates from Gabon and Russia, known as the Shunga-Francevillian Event (SFE). The result of the quantitatively constrained paleo-seawater [SO42−]sw suggests a crash of the seawater sulfate reservoir compared with that during the preceding LJE. However, the decreased δ34SCAS and increased CAS concentration towards the top of the study unit represent the recovery of seawater sulfate reservoir. The coordinated decline in δ34SCAS and δ13Ccarb values is likely related to enhanced oxidation of continental pyrite and organic matter in the aftermath of the LJE. The Huaiyincun Formation therefore represents a critical interval that recorded dynamic carbon and sulfur cycles after the LJE

Microbial biomass carbon and enzyme activities of urban soils in Beijing

Introduction To promote rational and sustainable use of soil resources and to maintain the urban soil quality, it is essential to assess urban ecosystem health. In this study, the microbiological properties of urban soils in Beijing and their spatial distribution patterns across the city were evaluated based on measurements of microbial biomass carbon and urease and invertase activities of the soils for the purpose of assessing the urban ecosystem health of Beijing. Materials and methods Grid sampling design, normal Kriging technique, and the multiple comparisons among different land use types were used in soil sampling and data treatment. The inherent chemical characteristics of urban soils in Beijing, e.g., soil pH, electronic conductivity, heavy metal contents, total N, P and K contents, and soil organic matter contents were detected. The size and diversity of microbial community and the extent of microbial activity in Beijing urban soils were measured as the microbial biomass carbon content and the ratio of microbial biomass carbon content to total soil organic carbon. Results and discussion The microbial community health measured in terms of microbial biomass carbon, urease, and invertase activities varied with the organic substrate and nutrient contents of the soils and were not adversely affected by the presence of heavy metals at p < 0.01. It was shown that the older and the biologically more stable part of city exhibited higher microbial activity levels than the more recently developed part of the city and the road areas of heavy traffic. It was concluded that the land use patterns in Beijing urban soils influenced the nature and activities of the microbial communities

Hyperphosphatemia in chronic kidney disease exacerbates atherosclerosis via a mannosidases-mediated complex-type conversion of SCAP N-glycans

Blood phosphate levels are linked to atherosclerotic cardiovascular disease in patients with chronic kidney disease (CKD), but the molecular mechanisms remain unclear. Emerging studies indicate an involvement of hyperphosphatemia in CKD accelerated atherogenesis through disturbed cholesterol homeostasis. Here, we investigated a potential atherogenic role of high phosphate concentrations acting through aberrant activation of sterol regulatory element-binding protein (SREBP) and cleavage-activating protein (SCAP)-SREBP2 signaling in patients with CKD, hyperphosphatemic apolipoprotein E (ApoE) knockout mice, and cultured vascular smooth muscle cells. Hyperphosphatemia correlated positively with increased atherosclerotic cardiovascular disease risk in Chinese patients with CKD and severe atheromatous lesions in the aortas of ApoE knockout mice. Mice arteries had elevated SCAP levels with aberrantly activated SCAP-SREBP2 signaling. Excess phosphate in vitro raised the activity of α-mannosidase, resulting in delayed SCAP degradation through promoting complex-type conversion of SCAP N-glycans. The retention of SCAP enhanced transactivation of SREBP2 and expression of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase, boosting intracellular cholesterol synthesis. Elevated α-mannosidase II activity was also observed in the aortas of ApoE knockout mice and the radial arteries of patients with uremia and hyperphosphatemia. High phosphate concentration in vitro elevated α-mannosidase II activity in the Golgi, enhanced complex-type conversion of SCAP N-glycans, thereby upregulating intracellular cholesterol synthesis. Thus, our studies explain how hyperphosphatemia independently accelerates atherosclerosis in CKD

Andreev reflection and tunneling spectrum in a superlattice of metal-superconductor junctions

The tunneling spectrum of an electron and a hole in a superlattice of NS junctions is computed using the BTK approach and the transfer matrix method. It shows sharp resonances at some energies above the superconducting gap. The sharper the resonance is the more layers the superlattice has. We find for the first time a mechanism to balance the incident and outgoing currents on the superlattice by averaging over the phase between the incident electron and the incident hole. This mechanism is more natural and physical than those in literatures.Comment: 4 pages,9 figure

Apatite-glaucony association in the Ediacaran Doushantuo Formation, South China and implications for marine redox conditions

Major phosphogenic events took place in the late Paleoproterozoic and the Ediacaran, both of which followed an episode of atmospheric oxygenation. These apparent coincidences have led to suggestions that the Precambrian phosphorus cycle was partly regulated by oceanic redox conditions, although direct evidence is lacking. In this paper, we report the discovery of glaucony in drill cores from the phosphorite-rich Ediacaran Doushantuo Formation at Weng'an, South China, which provides new insights into redox conditions and geochemical cycles during the deposition and early diagenesis of the lower Doushantuo Formation. The presence of flaser and lenticular bedding in the sandstones suggests deposition in a tidally-influenced shallow water environment. Apatite is present as millimeter-scale flasers in sandstones, but more commonly as intraclastic grains. Glaucony typically occurs as interstitial aggregates cementing and replacing detrital minerals and phosphatic grains, with an upsection decrease in abundance. The Doushantuo glauconies have consistently high K2O (7.5–9.6 wt%). In particular, phosphorite-hosted glaucony has generally higher total iron (TFe2O3) than sandstone-hosted glaucony, consistent with Al3+–Fe3+ substitution in the octahedral site, as supported by Raman peaks slightly shifted towards lower wavenumbers for higher Fe content. A decrease in detrital input probably resulted in limited Al availability during early diagenesis, which in turn led to the waning of glaucony upsection. The phosphate grains do not show any negative Ce anomalies, consistent with precipitation of authigenic apatite in suboxic environments with insignificant preferential remobilisation of Ce during deposition and early diagenesis. REE + Y features show variable diagenetic REE enrichment in phosphorites, but identical concave-down patterns. The wide occurrence of glaucony cement further documents the presence of a generally suboxic early diagenetic environment on the seafloor, which was in active exchange with bottom seawater. Slight fluctuations of redox states in the porewater and bottom water would have promoted the cycling of Fe, enrichment of phosphate and REE, and extensive glaucony authigenesis. Therefore, the glaucony-bearing phosphorites in the Doushantuo Formation are a direct result of Fe-redox driven diagenesis. Apatite-glaucony association likely forms in suboxic environments and is considered as a useful mineralogical proxy for paleoredox conditions on the Precambrian ocean floors

Study of Thermal Properties of Graphene-Based Structures Using the Force Constant Method

The thermal properties of graphene-based materials are theoretically investigated. The fourth-nearest neighbor force constant method for phonon properties is used in conjunction with both the Landauer ballistic and the non-equilibrium Green's function techniques for transport. Ballistic phonon transport is investigated for different structures including graphene, graphene antidot lattices, and graphene nanoribbons. We demonstrate that this particular methodology is suitable for robust and efficient investigation of phonon transport in graphene-based devices. This methodology is especially useful for investigations of thermoelectric and heat transport applications.Comment: 23 pages, 9 figures, 1 tabl