93 research outputs found
Geometry and Dynamics of Rolling Systems
Billiard systems, broadly speaking, may be regarded as models of mechanical systems in which rigid parts interact through elastic impulsive collision forces. When it is desired or necessary to account for linear/angular momentum exchange in collisions involving a spherical body, a type of billiard system often referred to as no-slip has been used. Previous work indicated that no-slip billiards resemble non-holonomic systems, specifically, systems consisting of a ball rolling on surface. In prior research, such connections were only observed numerically and were restricted to very special surfaces. In this thesis, it is shown that no-slip billiard and rolling systems are directly related to each other under very general conditions. Our main result shows that no-slip billiards are truly the non-holonomic counterpart to standard billiard systems. In addition, to the best of our knowledge, we use a novel from of the rolling equations, showing that these systems are a one-parameter perturbation of the geodesic equation on a Riemannian manifold. This opens up a new area of investigation in the theory of geometric dynamical systems, concerning what we call rolling flows. We introduced the main concepts related to the rolling flow but we leave further development for future research
Not All Features Matter: Enhancing Few-shot CLIP with Adaptive Prior Refinement
The popularity of Contrastive Language-Image Pre-training (CLIP) has
propelled its application to diverse downstream vision tasks. To improve its
capacity on downstream tasks, few-shot learning has become a widely-adopted
technique. However, existing methods either exhibit limited performance or
suffer from excessive learnable parameters. In this paper, we propose APE, an
Adaptive Prior rEfinement method for CLIP's pre-trained knowledge, which
achieves superior accuracy with high computational efficiency. Via a prior
refinement module, we analyze the inter-class disparity in the downstream data
and decouple the domain-specific knowledge from the CLIP-extracted cache model.
On top of that, we introduce two model variants, a training-free APE and a
training-required APE-T. We explore the trilateral affinities between the test
image, prior cache model, and textual representations, and only enable a
lightweight category-residual module to be trained. For the average accuracy
over 11 benchmarks, both APE and APE-T attain state-of-the-art and respectively
outperform the second-best by +1.59% and +1.99% under 16 shots with x30 less
learnable parameters.Comment: Code is available at https://github.com/yangyangyang127/AP
Native mass spectrometry and structural studies reveal modulation of MsbA–nucleotide interactions by lipids
The ATP-binding cassette (ABC) transporter, MsbA, plays a pivotal role in lipopolysaccharide (LPS) biogenesis by facilitating the transport of the LPS precursor lipooligosaccharide (LOS) from the cytoplasmic to the periplasmic leaflet of the inner membrane. Despite multiple studies shedding light on MsbA, the role of lipids in modulating MsbA-nucleotide interactions remains poorly understood. Here we use native mass spectrometry (MS) to investigate and resolve nucleotide and lipid binding to MsbA, demonstrating that the transporter has a higher affinity for adenosine 5’-diphosphate (ADP). Moreover, native MS shows the LPS-precursor 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo)2-lipid A (KDL) can tune the selectivity of MsbA for adenosine 5’-triphosphate (ATP) over ADP. Guided by these studies, four open, inward-facing structures of MsbA are determined that vary in their openness. We also report a 2.7 Å-resolution structure of MsbA in an open, outward-facing conformation that is not only bound to KDL at the exterior site, but with the nucleotide binding domains (NBDs) adopting a distinct nucleotide-free structure. The results obtained from this study offer valuable insight and snapshots of MsbA during the transport cycle
Experimental study and mechanism analysis of high-pressure water jet for mud cake cutting during shield tunneling
When the opening rate of the cutter head of tunnel boring machines is insufficient for the removal of excavated soil in a timely manner, the soil tends to accumulate in front of the cutter head and inside the earth or slurry chamber, leading to mud caking. High-pressure water jetting is an effective method for removing mud cakes. This study explored the influence of high-pressure water jet parameters on the efficiency of mud cake cleaning by using highly weathered argillaceous siltstone as experimental materials. Mud cake compaction equipment and high-pressure water jetting devices were developed. In addition, the impact of jetting parameters such as jet pressure and flow rate on the mud cake cutting performance was investigated. The results indicated that with an increase in the erosion distance, the cutting width of the mud cake first increased and then gradually decreased to zero, while the cutting depth progressively diminished. Under the same jet pressure, when the flow rate increased from 49.1 L/min to 110 L/min, the cutting width of the high-pressure water jet increased. With further increase in the flow rate from 110 L/min to 202.8 L/min, the cutting width decreased and the cutting depth increased. Under the same jet flow, the increase in water pressure resulted in greater cutting width and depth
Research Progress of Ionic Thermoelectric Materials for Energy Harvesting
Thermoelectric material is a kind of functional material that can mutually convert heat energy and electric energy. It can convert low-grade heat energy (less than 130°C) into electric energy. Compared with traditional electronic thermoelectric materials, ionic thermoelectric materials have higher performance. The Seebeck coefficient can generate 2–3 orders of magnitude higher ionic thermoelectric potential than electronic thermoelectric materials, so it has good application prospects in small thermoelectric generators and solar power generation. According to the thermoelectric conversion mechanism, ionic thermoelectric materials can be divided into ionic thermoelectric materials based on the Soret effect and thermocouple effect. They are widely used in pyrogen batteries and ionic thermoelectric capacitors. The latest two types of ionic thermoelectric materials are in this article. The research progress is explained, and the problems and challenges of ionic thermoelectric materials and the future development direction are also put forward
Anomalous size effects of effective stiffnesses in bistable counter-rotating mechanical metamaterials
Counter-rotating mechanical metamaterials have previously been found to have
anomalous characteristics or functions such as auxetics effects, shape
changers, and soliton transports, which are all under monostable conditions.
The properties of counter-rotating mechanical metamaterials under bistable
conditions have not yet been explored. Here, we found that for a bistable
counter-rotating metamaterial chain, the effective stiffnesses of the two
steady states are different in the chain with even-numbered nodes. For the
chain with odd-numbered nodes, the effective stiffnesses corresponding to the
two steady states are exactly the same. This special property is not
characterized by the characteristic attenuation lengths of the underlying
mechanism, but depends on the different symmetries of the underlying mechanism
of the chains with odd and even nodes. In addition, the relationship between
the abnormal non-monotonic size effect and equilibrium angle are clarified.
More interestingly, for one-dimensional chains with even-numbered nodes, the
size effect of effective stiffness bifurcates at a specific equilibrium angle,
and the according mechanisms are revealed
Towards a unified understanding of uncertainty quantification in traffic flow forecasting
Uncertainty is an essential consideration for time series forecasting tasks. In this work, we focus on quantifying the uncertainty of traffic forecasting from a unified perspective. We develop a novel traffic forecasting framework, namely Deep Spatio-Temporal Uncertainty Quantification (DeepSTUQ), which can estimate both aleatoric and epistemic uncertainty. Specifically, we first leverage a spatio-temporal model to model the complex spatio-temporal correlations of traffic data. Subsequently, two independent sub-neural networks maximizing the heterogeneous log-likelihood are developed to estimate aleatoric uncertainty. To estimate epistemic uncertainty, we combine the merits of variational inference and deep ensembling by integrating the Monte Carlo dropout and the Adaptive Weight Averaging re-training methods, respectively. Furthermore, to relax the Gaussianity assumption, mitigate overfitting, and improve horizon-wise uncertainty quantification performance, we define a new calibration method called Multi-horizon Conformal Calibration (MHCC). Finally, we provide a theoretical analysis of the proposed unified approach based on the PAC-Bayes theory. Extensive experiments are conducted on four public datasets, and the empirical results suggest that the proposed method outperforms state-of-the-art methods in terms of both point prediction and uncertainty quantification
Sox2 Sustains Recruitment of Oligodendrocyte Progenitor Cells following CNS Demyelination and Primes Them for Differentiation during Remyelination.
UNLABELLED: The Sox family of transcription factors have been widely studied in the context of oligodendrocyte development. However, comparatively little is known about the role of Sox2, especially during CNS remyelination. Here we show that the expression of Sox2 occurs in oligodendrocyte progenitor cells (OPCs) in rodent models during myelination and in activated adult OPCs responding to demyelination, and is also detected in multiple sclerosis lesions. In normal adult white matter of both mice and rats, it is neither expressed by adult OPCs nor by oligodendrocytes (although it is expressed by a subpopulation of adult astrocytes). Overexpression of Sox2 in rat OPCs in vitro maintains the cells in a proliferative state and inhibits differentiation, while Sox2 knockout results in decreased OPC proliferation and survival, suggesting that Sox2 contributes to the expansion of OPCs during the recruitment phase of remyelination. Loss of function in cultured mouse OPCs also results in an impaired ability to undergo normal differentiation in response to differentiation signals, suggesting that Sox2 expression in activated OPCs also primes these cells to eventually undergo differentiation. In vivo studies on remyelination following experimental toxin-induced demyelination in mice with inducible loss of Sox2 revealed impaired remyelination, which was largely due to a profound attenuation of OPC recruitment and likely also due to impaired differentiation. Our results reveal a key role of Sox2 expression in OPCs responding to demyelination, enabling them to effectively contribute to remyelination. SIGNIFICANCE STATEMENT: Understanding the mechanisms of CNS remyelination is central to developing effective means by which this process can be therapeutically enhanced in chronic demyelinating diseases such as multiple sclerosis. In this study, we describe the role of Sox2, a transcription factor widely implicated in stem cell biology, in CNS myelination and remyelination. We show how Sox2 is expressed in oligodendrocyte progenitor cells (OPCs) preparing to undergo differentiation, allowing them to undergo proliferation and priming them for subsequent differentiation. Although Sox2 is unlikely to be a direct therapeutic target, these data nevertheless provide more information on how OPC differentiation is controlled and therefore enriches our understanding of this important CNS regenerative process.This work was mainly supported by the UK Multiple Sclerosis Society.This is the final version of the article. It first appeared from the Society for Neuroscience via http://dx.doi.org/10.1523/JNEUROSCI.3655-14.201
Demineralized dentin matrix promotes gingival healing in alveolar ridge preservation of premolars extracted for orthodontic reason: a split-mouth study
ObjectiveThe purpose of this study was to prospectively evaluate the efficacy of a demineralized dentin matrix (DDM) in decreasing the initial inflammatory response of the gingiva and facilitating the repair and regeneration of soft tissue in alveolar ridge preservation.MethodsThis clinical study employed a split-mouth design. Fourteen patients with a total of forty-four sites underwent extraction and alveolar ridge preservation (ARP) procedures. A Bilaterally symmetrical extraction operation were conducted on the premolars of each patient. The experimental group received DDM as a graft material for ARP, while the control group underwent natural healing. Within the first month postoperatively, the pain condition, color, and swelling status of the extraction sites were initially assessed at different time points Subsequently, measurements were taken for buccal gingival margin height, buccal-lingual width, extraction socket contour, and the extraction socket area and healing rate were digitally measured. Additionally, Alcian Blue staining was used for histological evaluation of the content during alveolar socket healing.ResultsBoth groups experienced uneventful healing, with no adverse reactions observed at any of the extraction sites. The differences in VAS pain scores between the two groups postoperatively were not statistically significant. In the early stage of gingival tissue healing (3 days postoperatively), there were statistically significant differences in gingival condition and buccal gingival margin height between the two groups. In the later stage of gingival tissue healing (7, 14, and 30 days postoperatively), there were statistically significant differences in buccal-lingual width, extraction socket healing area, and healing rate between the two groups. Furthermore, the histological results from Alcian Blue staining suggested that the experimental group may play a significant role in promoting gingival tissue healing, possibly by regulating inflammatory responses when compared to the control group.ConclusionThe application of DDM in alveolar ridge preservation has been found to diminish initial gingival inflammation after tooth extraction. Additionally, it has shown the ability to accelerate early gingival soft tissue healing and preserve its anatomical contour.Clinical trial registrationchictr.org.cn, identifier ChiCTR2100050650
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