Non-Markovian quantum state diffusion for an open quantum system in fermionic environments

Non-Markovian quantum state diffusion (NMQSD) provides a powerful approach to the dynamics of an open quantum system in bosonic environments. Here we develop an NMQSD method to study the open quantum system in fermionic environments. This problem involves anticommutative noise functions (i.e., Grassmann variables) that are intrinsically different from the noise functions of bosonic baths. We obtain the NMQSD equation for quantum states of the system and the non-Markovian master equation. Moreover, we apply this NMQSD method to single and double quantum-dot systems.Comment: 9 pages, 1 figur

Characterizing the stocks, flows, and carbon impact of dockless sharing bikes in China

The booming dockless sharing bikes (DSBs) in China, as a new sharing economy business model, have attracted increasing public and academic attention after 2015. The impact of DSBs development on the stocks and flows of bikes and the resource and climate consequences of short-lived DSBs, however, remain poorly understood. In this study, we characterized the stocks and flows of both DSBs and regular private bikes in China from 1950 to 2020 and evaluated the carbon cost and benefit of booming DSBs. We found China's bike consumption and stock decreased slightly after a fast development from the late 1970s and then a peak in the mid-1990s, resulting in a relatively low ownership of approximately 0.3 unit per person and 70% of production being exported in recent years. Despite a temporal boost, the unsustainable development of DSBs may affect the bike industry in the long term, because of its skyrocketing market share (from less than 1% to 80%) and short lifetime. Nevertheless, DSBs development still leads to an overall climate gain in China, due to its higher stock efficiency and potentials to substitute more carbon intensive trips. We suggest an urgent need for more empirical studies on the use (e.g., substitution ratio for other transportation models) of DSBs in China and a necessity for better management of DSB development with efforts of all relevant stakeholders

Dissipationless Anomalous Hall Current in Fe100−x(SiO2)xFe_{100-x}(SiO_2)_x Films

The observation of dissipationless anomalous Hall current is one of the experimental evidences to confirm the intrinsic origin of anomalous Hall effect. To study the origin of anomalous Hall effect in iron, Fe$_{100-x}$(SiO$_{2}$)$_{x}$ granular films with volume fraction of SiO$_{2}$ 0\le x \le 40.51 were fabricated using co-sputtering. Hall and longitudinal resistivities were measured in the temperature range 5 to 350 K with magnetic fields up to 5 Tesla. As x increased from 0 to 40.51, the anomalous Hall resistivity and longitudinal resistivity increased about 4 and 3 orders in magnitude, respectively. Analysis of the results revealed that the normalized anomalous Hall conductivity is a constant for all the samples, the evidence of dissipationless anomalous Hall current in Fe.Comment: 17 pages, 5 figures; http://link.aps.org/doi/10.1103/PhysRevB.83.20531

Load Magnitude and Locomotion Strategy Alters Knee Mechanics in Recruit-Aged Women

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A multiscale agent-based in silico model of liver fibrosis progression

Chronic hepatic inflammation involves a complex interplay of inflammatory and mechanical influences, ultimately manifesting in a characteristic histopathology of liver fibrosis. We created an agent-based model (ABM) of liver tissue in order to computationally examine the consequence of liver inflammation. Our liver fibrosis ABM (LFABM) is comprised of literature-derived rules describing molecular and histopathological aspects of inflammation and fibrosis in a section of chemically injured liver. Hepatocytes are modeled as agents within hexagonal lobules. Injury triggers an inflammatory reaction, which leads to activation of local Kupffer cells and recruitment of monocytes from circulation. Portal fibroblasts and hepatic stellate cells are activated locally by the products of inflammation. The various agents in the simulation are regulated by above-threshold concentrations of pro- and anti-inflammatory cytokines and damage-associated molecular pattern molecules. The simulation progresses from chronic inflammation to collagen deposition, exhibiting periportal fibrosis followed by bridging fibrosis, and culminating in disruption of the regular lobular structure. The ABM exhibited key histopathological features observed in liver sections from rats treated with carbon tetrachloride (CCl4). An in silico "tension test" for the hepatic lobules predicted an overall increase in tissue stiffness, in line with clinical elastography literature and published studies in CCl4-treated rats. Therapy simulations suggested differential anti-fibrotic effects of neutralizing tumor necrosis factor alpha vs. enhancing M2 Kupffer cells. We conclude that a computational model of liver inflammation on a structural skeleton of physical forces can recapitulate key histopathological and macroscopic properties of CCl4-injured liver. This multiscale approach linking molecular and chemomechanical stimuli enables a model that could be used to gain translationally relevant insights into liver fibrosis

Stochastic assembly in a subtropical forest chronosequence: evidence from contrasting changes of species, phylogenetic and functional dissimilarity over succession

This is the final version. Available on open access from Springer Verlag via the DOI in this recordDeterministic and stochastic processes jointly determine the community dynamics of forest succession. However, it has been widely held in previous studies that deterministic processes dominate forest succession. Furthermore, inference of mechanisms for community assembly may be misleading if based on a single axis of diversity alone. In this study, we evaluated the relative roles of deterministic and stochastic processes along a disturbance gradient by integrating species, functional, and phylogenetic beta diversity in a subtropical forest chronosequence in Southeastern China. We found a general pattern of increasing species turnover, but little-to-no change in phylogenetic and functional turnover over succession at two spatial scales. Meanwhile, the phylogenetic and functional beta diversity were not significantly different from random expectation. This result suggested a dominance of stochastic assembly, contrary to the general expectation that deterministic processes dominate forest succession. On the other hand, we found significant interactions of environment and disturbance and limited evidence for significant deviations of phylogenetic or functional turnover from random expectations for different size classes. This result provided weak evidence of deterministic processes over succession. Stochastic assembly of forest succession suggests that post-disturbance restoration may be largely unpredictable and difficult to control in subtropical forests.This study was supported financially by National Key Research and Development Project of China (2016YFC0500202) the National Natural Science Foundation of China (31170401), and the Earthwatch Institute program “Quantify and monitor carbon pools and fluxes to assess the impact of climate change on subtropical forests under different anthropogenic disturbances”. NGS was supported by two NSF USA-China Dimensions of Biodiversity Grants (DEB - 1046113; DEB - 1241136)

New Roles for Old Glue: Astrocyte Function in Synaptic Plasticity and Neurological Disorders

Previously believed to solely play a supportive role in the central nervous system, astrocytes are now considered active players in normal brain function. Evidence in recent decades extends their contributions beyond the classically held brain glue role; it’s now known that astrocytes act as a unique excitable component with functions extending into local network modulation, synaptic plasticity, and memory formation, and postinjury repair. In this review article, we highlight our growing understanding of astrocyte function and physiology, the increasing role of gliotransmitters in neuron-glia communication, and the role of astrocytes in modulating synaptic plasticity and cognitive function. Owing to the duality of both beneficial and deleterious roles attributed to astrocytes, we also discuss the implications of this new knowledge as it applies to neurological disorders including Alzheimer disease, epilepsy, and schizophrenia