New Benchmarking Shows Limited Generalization Power of TCR Antigenic Epitope Prediction Models
新基准测试显示TCR抗原表位预测模型的泛化能力有限
AI总结 本文通过构建两类严格定义的未见基准数据集,评估了T细胞受体(TCR)抗原特异性预测模型的性能,发现现有模型泛化能力有限,并提出了改进框架。
新基准测试显示TCR抗原表位预测模型的泛化能力有限
Yiming Liao, Yiheng Li, Ning Jiang, Bo Li, Keke Chen
AI总结 本文通过构建两类严格定义的未见基准数据集,评估了T细胞受体(TCR)抗原特异性预测模型的性能,发现现有模型泛化能力有限,并提出了改进框架。
准确计算预测T细胞受体(TCR)抗原特异性将改变T细胞生物学研究,并实现可扩展的免疫工程,但现有模型缺乏足够的灵敏度和特异性,难以广泛应用。一个主要限制是缺乏严格定义的、未见过的基准数据集,无法对模型性能和泛化能力进行无偏评估。在此,我们描述了两类满足此标准的互补数据集,并认为它们既为模型评估提供了稳健框架,也为下一代TCR-抗原预测算法的开发奠定了基础。
Accurate computational prediction of T cell receptor (TCR) antigen specificity would transform the study of T cell biology and enable scalable immune engineering, yet existing models lack sufficient sensitivity and specificity for broad applications. A major limitation is the absence of rigorously defined, unseen benchmark datasets that allow unbiased evaluation of model performance and generalizability. Here, we describe two complementary classes of datasets that meet this criterion and argue that they provide both a robust framework for model assessment and a foundation for next-generation TCR-antigen prediction algorithm development.
AF_Cache:用于高通量蛋白质-蛋白质相互作用预测的高效AlphaFold流水线
Sarah Narrowe, Arne Elofsson Claudio Mirabello
AI总结 提出AF_Cache流水线,通过GPU加速MSA生成、特征缓存和序列长度分桶,将AlphaFold2推理时间缩短约2倍,MSA生成加速高达13倍,实现大规模蛋白质相互作用的高通量预测。
动机:准确预测蛋白质-蛋白质相互作用对于理解生物过程至关重要,而AlphaFold2和AlphaFold3等最新进展使得基于结构的相互作用预测达到了前所未有的精度。然而,这些方法的高计算成本——主要由基于CPU的重复多序列比对(MSA)生成以及AlphaFold2的重复模型重新编译驱动——限制了它们在大规模、高通量环境中的适用性。这需要一种既能保持预测性能又能大幅减少运行时间的高效流水线。 结果:我们提出了AF_Cache,一个用于使用AlphaFold2和AlphaFold3加速蛋白质-蛋白质相互作用预测的高通量Nextflow流水线。AF_Cache结合了使用MMseqs2的GPU加速MSA生成、消除冗余比对计算的特征缓存,以及最小化重复JAX编译的序列长度分桶。在包含5,050对人类线粒体蛋白质对的数据集上的基准测试表明,AlphaFold2的推理时间减少了约2倍,MSA生成加速高达13倍。AF_Cache实现了高效的大规模相互作用筛选,并为在高通量应用中部署基于AlphaFold的方法提供了一个实用框架。 可用性和实现:代码和Nextflow流水线可在GitHub上获取:https://github.com/clami66/AF_cache。用于重现论文结果、MSA和预测模型的代码可在Zenodo上找到:https://zenodo.org/records/20478892
Motivation: Accurate prediction of protein-protein interactions is essential for understanding biological processes, and recent advances such as AlphaFold2 and AlphaFold3 have enabled structure-based interaction prediction at unprecedented accuracy. However, the high computational cost of these methods, driven primarily by CPU-based repeated multiple sequence alignment (MSA) generation and, for AlphaFold2, repeated model recompilations, limits their applicability in large-scale, high-throughput settings. This creates a need for efficient pipelines that retain predictive performance while substantially reducing runtime. Results: We present AF_Cache, a high-throughput Nextflow pipeline for accelerating protein-protein interaction prediction using AlphaFold2 and AlphaFold3. AF_Cache combines GPU-accelerated MSA generation with MMseqs2, feature caching to eliminate redundant alignment computations, and sequence length bucketing to minimise repeated JAX compilations. Benchmarking on a dataset of 5,050 human mitochondrial protein pairs demonstrates a $\sim$2-fold reduction in inference time for AlphaFold2 and up to a 13-fold speedup of the MSA generation. AF\_Cache enables efficient large-scale interaction screening and provides a practical framework for deploying AlphaFold-based methods in high-throughput applications. Availability and implementation: The code and Nextflow pipeline are available on GitHub here: https://github.com/clami66/AF_cache. The code for reproducing the results of the paper, the MSAs, and the predicted models can be found at Zenodo: https://zenodo.org/records/20478892
LDARNet: 用于基因组建模的DNA自适应表示网络与可学习分词
Daria Ledneva, Denis Kuznetsov
AI总结 提出LDARNet,一种结合动态分块和双向路由的120M参数层次基因组基础模型,在27个任务中优于更大模型,并发现学习到的边界与生物学基序对齐。
基因组基础模型越来越多地采用大型语言模型架构,但几乎普遍依赖于固定的分词方案,如$k$-mers、BPE或单核苷酸,这些方案强加了可能掩盖生物学相关结构的任意序列边界。我们提出了LDARNet,一个120M参数的层次基因组基础模型,它将H-Net风格的动态分块从自回归生成适应到掩码语言建模,结合了BiMamba-2状态空间层与局部注意力、双向路由以及基于比值的正则化器,以在无监督的情况下诱导自适应标记边界。在来自Nucleotide Transformer和Genomic Benchmarks套件的27个任务上进行微调后,LDARNet在紧凑模型(<300M参数)中取得了11/18的胜率,并在5个组蛋白修饰任务上取得了最先进的结果,优于高达20倍大的模型。一个FLOPs匹配的对照实验将学习到的路由确定为这些增益的来源:在相同计算量下,学习到的边界在组蛋白任务上比固定网格边界高出多达14个百分点。进一步的核苷酸分辨率分析表明,学习到的边界在无监督的情况下与典型的启动子基序和剪接连接点对齐,为基因组基础模型中的自适应分词提供了生物学解释。
Genomic foundation models increasingly adopt large language model architectures, yet almost universally rely on fixed tokenization schemes such as $k$-mers, BPE, or single nucleotides, which impose arbitrary sequence boundaries that may obscure biologically relevant structure. We present LDARNet, a 120M-parameter hierarchical genomic foundation model that adapts H-Net-style dynamic chunking from autoregressive generation to masked language modeling, combining BiMamba-2 state-space layers with local attention, bidirectional routing, and a ratio-based regularizer to induce adaptive token boundaries without supervision. Fine-tuned on 27 tasks from the Nucleotide Transformer and Genomic Benchmarks suites, LDARNet achieves 11/18 wins among compact models ($<$300M parameters) and state-of-the-art results on 5 histone modification tasks, outperforming models up to 20$\times$ larger. A FLOPs-matched controlled experiment isolates learned routing as the source of these gains: learned boundaries beat fixed-grid boundaries by up to 14 percentage points on histone tasks at identical compute. Nucleotide-resolution analysis further shows that the learned boundaries align with canonical promoter motifs and splice junctions without supervision, providing a biological interpretation for adaptive tokenization in genomic foundation models.
树内演化的拟生灭过程:比较系统发育学中的应用
Habtu Kiros Nigus, Barbara R. Holland, Malgorzata M. O'Reilly
AI总结 提出一种在系统发育树中演化的拟生灭过程模型,通过离散化连续性状并开发递归算法计算似然,应用于哺乳动物体型和分布区演化的实证分析。
我们考虑一个拟生灭过程(QBD),它在包含复制时间和潜在部分观测状态的树内某些固定时间点进行复制。我们通过离散化连续性状来获得QBD水平变量,然后使用相位变量对底层环境的动态进行建模。在此,我们扩展了Soewongsono等人的框架以实现更一般的分析。我们开发了一种高效的递归算法来计算该模型下观测树的似然,并构建了几个数值示例以说明其应用潜力。通过合成数据示例,我们展示了一系列可能的行为,这些行为可以通过该方法进行建模。此外,我们将该框架应用于比较系统发育学中的两个实证示例(跨越49种哺乳动物的系统发育的分布区面积和体型性状的演化),以获得对这些连续性状演化的不同见解。在此设置中,QBD的复制代表物种形成,连续性状演化在离散状态空间中建模。在我们的实证示例中,我们探讨了不同参数选择对观测给定系统发育树及其尖端观测水平的相应似然的影响。
We consider a quasi-birth-and-process (QBD) that duplicates itself at some fixed times within a tree that contains information about duplication times and potentially partially observed states. We analyse a continuous trait by discretising it to obtain the QBD level variable. Then, the phase variable is used to model the dynamics of the underlying environment. Here, we extend the framework of Soewongsono et al. to enable a more general analysis. We develop an efficient recursive algorithm for computing the likelihood of an observed tree under this model and construct several numerical examples to illustrate its application potential. Through our synthetic data examples, we show a range of potential behaviours that could be modelled with this approach. Further, we apply the framework to two empirical examples from comparative phylogenetics (the evolution of range area and body size traits across a phylogeny of 49 mammals) to gain different insights into the evolution of these continuous traits. In this setting duplication of the QBD represents speciation and continuous trait evolution is modelled in a discretised state space. In our empirical examples, we explore the impact of different parameter choices on the corresponding likelihood of observing a given phylogenetic tree and the observed levels at its tips.
离散信号介导递归神经网络的混沌正则化
Jan Bauer, Christian Keup, Jonathan Kadmon, Moritz Helias
AI总结 通过结合核方法和动态平均场理论,揭示了混沌动力学如何在递归神经网络中引入局部粗糙度并保持全局平滑性,从而作为内在正则化器增强泛化能力,并解释了混沌网络如何维持平滑的群体编码。
皮层回路在内在混沌状态下运行,即使输入的微小变化也可能导致神经反应的巨大差异。然而,值得注意的是,大脑中的群体编码随感觉刺激平滑变化,形成连贯的表征流形。混沌网络如何维持这种稳定的编码?在这里,我们建立了一个理论框架,将递归网络的微观混沌与神经表征的宏观几何联系起来。结合核方法和动态平均场理论,我们表明混沌动力学在较大刺激变化范围内保持全局平滑性的同时,会引入局部粗糙度(在小尺度上产生尖锐扭曲)。这种结构特性作为一种内在正则化器,在保持表达性的同时增强泛化能力。此外,我们展示了混沌网络如何自然产生幂律谱特征,与皮层记录中的实验观察高度吻合。这些结果解释了混沌脉冲网络如何维持平滑、可微分的群体编码,并建立了一个将网络动力学、计算结构和记录的神经活动联系起来的理论框架。
Cortical circuits operate in a regime of intrinsic chaos, where even tiny changes in input can lead to divergent neural responses. Yet, remarkably, population codes in the brain vary smoothly with sensory stimuli, forming coherent representational manifolds. How can chaotic networks sustain such stable coding? Here, we develop a theoretical framework that links the microscopic chaos of recurrent networks to the macroscopic geometry of neural representations. Combining kernel methods with dynamical mean-field theory, we show that chaotic dynamics induce local roughness (introducing sharp distortions at small scales) while preserving global smoothness across larger stimulus variations. This structural property acts as an intrinsic regularizer, enhancing generalization while maintaining expressivity. Moreover, we show how chaotic networks naturally produce power-law spectral signatures, closely matching experimental observations in cortical recordings. These results explain how chaotic spiking networks can sustain smooth, differentiable population codes and establish a theoretical framework linking network dynamics, computational structure, and recorded neural activity.
心脏瓣膜力学与功能的八面体纤维本构模型
Nishan Parvez, Prashant K. Purohit, Wensi Wu
AI总结 提出一种各向异性超弹性模型,考虑纤维网络在拉伸和压缩下的贡献,通过逆向有限元与自动微分校准,揭示纤维取向和刚度变化对二尖瓣闭合及反流的影响。
纤维软组织从细胞外基质纤维网络中获得非线性力学响应,其组织导致应变硬化、反向Poynting效应和各向异性力学行为。受这些耦合特征的启发,我们为纤维生物组织开发了一种各向异性超弹性模型,该模型考虑了纤维网络在拉伸和压缩变形下的贡献。我们使用逆向有限元方法,结合自动微分以促进高效参数校准,将模型校准到二尖瓣叶的实验数据。使用校准后的模型,我们研究了各向异性和纤维重新取向如何影响生理载荷下的瓣膜变形。结果表明,径向更大的叶瓣顺应性产生适当的瓣膜闭合,而局部纤维重新取向导致应力集中,可能促进渐进性功能退化。使周向比径向更顺应性的纤维重新取向会损害瓣膜闭合并导致二尖瓣反流。腱索软化进一步放大了这种反流反应的严重程度。这些发现表明,纤维结构的改变,尤其是伴随腱索退化时,可能促进二尖瓣关闭不全的发生和进展。
Fibrous soft tissues derive their nonlinear mechanical response from networks of extracellular matrix fibers, whose organization gives rise to strain stiffening, the reverse Poynting effect, and anisotropic mechanical behavior. Motivated by these coupled features, we develop an anisotropic hyperelastic model for fibrous biological tissues that accounts for the contribution of the fiber network under both tensile and compressive deformation. We calibrate the model to experimental data for mitral valve leaflets using an inverse finite element approach that is coupled to automatic differentiation to facilitate efficient parameter calibration. Using the calibrated model, we investigate how anisotropy and fiber reorientation affect valve deformation under physiological loading. The results show that greater leaflet compliance in the radial direction yields proper valve closure, whereas localized fiber reorientation leads to stress concentrations that may promote progressive functional degradation. Fiber reorientation that makes the circumferential direction more compliant than the radial direction compromises valve closure and leads to mitral regurgitation. Chordal softening further amplifies the severity of this regurgitant response. These findings suggest that alterations in fiber architecture, especially when accompanied by chordal degradation, can contribute to the onset and progression of mitral valve incompetence.
EpiFormer: 通过几何深度学习学习抗原-抗体相互作用进行表位预测
Mansoor Ahmed, Huirong Chai, Haoxin Wang, Hemanth Venkateswara, Murray Patterson
AI总结 提出EpiFormer编码器-解码器框架,通过GNN层间交叉注意力实现抗原-抗体双向信息流,结合稀疏感知目标,在表位预测任务上F1分数提升超40%。
抗体通过结合称为表位的特定表面区域来中和外来抗原。计算表位预测对于理解免疫识别和指导抗体工程至关重要。然而,现有方法面临三个基本挑战:抗体感知模型独立编码每条链并在后期才进行组合,无法捕捉定义结合界面的共依赖结构特征;而严重的类别不平衡和已知抗体-抗原复合物的稀缺使得标准训练目标无效。我们提出EpiFormer,一个通用的编码器-解码器框架,联合解决这些挑战。我们的关键设计原则是在GNN编码层内进行交错交叉注意力,使得抗原-抗体信息流贯穿整个表示学习过程,而不仅仅在输出时。这种早期融合原则与主干无关,从简单的GCN到等变模型,在各种GNN架构上都能提供一致的改进。我们进一步表明,当与早期融合架构配对时,稀疏感知目标对于表位预测任务是有效的。EpiFormer在标准基准上的F1分数比之前的最佳方法提高了40%以上,展示了泛化能力和跨数据集迁移性。值得注意的是,EpiFormer发现已知的生物学原理作为端到端训练的涌现行为,其中学习到的交叉注意力门控倾向于抗原到抗体的信息流,与两条链在结合界面的不对称角色一致,并且模型对几何特征而非进化特征的偏好与已建立的发现(表位残基并非进化保守)一致。源代码可在https://github.com/mansoor181/epiformer.git获取。
Antibodies neutralize foreign antigens by binding to specific surface regions called epitopes. Computational epitope prediction is critical for understanding immune recognition and guiding antibody engineering. However, existing methods face three fundamental challenges: antibody-aware models encode each chain independently and combine them only at a late stage, failing to capture co-dependent structural features that define binding interfaces, whereas severe class imbalance and scarcity of known antibody-antigen complexes render standard training objectives ineffective. We propose EpiFormer, a general encoder-decoder framework that addresses these challenges jointly. Our key design principle is interleaved cross-attention within GNN encoding layers, enabling bidirectional antigen-antibody information flow throughout representation learning rather than only at the output. This early-fusion principle is backbone-agnostic, providing consistent gains across GNN architectures from simple GCNs to equivariant models. We further show that sparsity-aware objectives are effective when paired with early-fusion architectures for the epitope prediction task. EpiFormer improves over the previous best method by over 40% in F1 score on standard benchmarks, demonstrating generalizability and cross-dataset transferability. Notably, EpiFormer discovers known biological principles as emergent behaviors of end-to-end training, where the learned cross-attention gates favor antigen-to-antibody information flow, consistent with the asymmetric roles of the two chains at the binding interface, and the model's preference for geometric over evolutionary features aligns with the established finding that epitope residues are not evolutionarily conserved. The source code is available at: https://github.com/mansoor181/epiformer.git
SC-TauPath:一种用于映射阿尔茨海默病中tau蛋白传播路径的结构连接归因框架
Jing Zhang, Norman Scheel, Minheng Chen, Tong Chen, Yanjun Lyu, David C. Zhu, Rong Zhang, Dajiang Zhu
AI总结 提出SC-TauPath框架,结合网络扩散模型增强的多层感知机和梯度×输入归因方法,从体内神经影像数据中映射tau蛋白传播路径,并验证了与Braak分期解剖学的一致性。
理解结构连接如何与阿尔茨海默病(AD)中的tau蛋白传播相关联仍然是一个核心未解问题,然而现有的计算模型要么严重依赖生物物理假设,要么缺乏神经生物学可解释的路径图。我们提出了SC-TauPath,一个结构连接(SC)归因框架,用于从体内神经影像数据中映射tau蛋白传播路径。SC-TauPath将网络扩散模型(NDM)增强的多层感知机与梯度×输入归因相结合,以评分每个SC边对tau预测的贡献,然后将这些归因分数转化为多尺度路径图(骨干边、高流量路径和枢纽ROI),这验证了已建立的Braak分期解剖学。应用于234名ADNI参与者,这些参与者具有配对的DTI SC和18F-Flortaucipir PET数据,SC-TauPath实现了强交叉验证的tau预测,并产生了与已建立的Braak分期解剖学一致的基于归因的路径图,表明SC编码了AD中区域tau分布的特定空间信息。
Understanding how structural connections are associated with tau propagation in Alzheimer's disease (AD) remains a central open question, yet existing computational models either rely heavily on biophysical assumptions or lack neurobiologically interpretable pathway maps. We present SC-TauPath, a structural connectivity (SC) attribution framework that maps tau propagation pathways from in vivo neuroimaging data. SC-TauPath combines a Network Diffusion Model (NDM)-augmented multilayer perceptron with gradient $\times$ input attribution to score each SC edge's contribution to tau prediction, then translates these attribution scores into multi-scale pathway maps (backbone edges, high-traffic routes, and hub ROIs), which validates established Braak staging anatomy. Applied to 234 ADNI participants with paired DTI SC and 18F-Flortaucipir PET, SC-TauPath achieves strong cross-validated tau prediction and yields attribution-based pathway maps consistent with established Braak staging anatomy, demonstrating that SC encode spatially specific information about regional tau distribution in AD.
通过图神经网络进行PROTAC介导的蛋白质降解性的结构感知预测
Bryan Cheng, Austin Jin
AI总结 提出DegradoMap,一种仅利用蛋白质结构和E3连接酶身份预测PROTAC降解性的图神经网络,在目标未见和E3未见评估中优于基线,并推荐最优E3连接酶。
蛋白水解靶向嵌合体(PROTACs)可以选择性降解致病蛋白,然而预测哪些靶点适合降解仍然是一个关键瓶颈:现有计算方法需要完整的PROTAC分子结构,而该信息在合成前不可用。我们提出DegradoMap,一种图神经网络,仅从蛋白质结构和E3连接酶身份预测PROTAC介导的降解性——这是靶点选择阶段可用的最小信息。该模型通过赖氨酸加权图池化(每蛋白质归一化)编码生物物理先验,通过交叉注意力建模蛋白质-E3兼容性,并整合来自癌症依赖性图谱的细胞环境。在PROTAC-8K基准(3,101个样本,155个靶点,10种E3连接酶)上,DegradoMap在靶点未见评估中达到0.646±0.124 AUROC(最佳种子:0.7449),在CRBN→VHL E3未见迁移中达到0.811 AUROC,优于GNN和机器学习基线。该模型还以74%的Hit@3准确率推荐最优E3连接酶。两个发现具有更广泛的意义:对于此标量预测任务,E(3)-等变架构的性能低于更简单的不变设计;ESM-2嵌入仅在仔细正则化下提升峰值性能——简单集成失败。DegradoMap为降解性评估提供合成前的计算指导;其良好校准的置信度分数(ECE=0.029,靶点未见)使从业者能够优先选择高置信度预测进行实验验证。然而,高种子方差(std=0.124)和有限的E3覆盖范围需要集成以实现可靠部署。
Proteolysis-targeting chimeras (PROTACs) can selectively degrade disease-causing proteins, yet predicting which targets are amenable to degradation remains a critical bottleneck: existing computational methods require the complete PROTAC molecular structure, information unavailable before synthesis. We present DegradoMap, a graph neural network that predicts PROTAC-mediated degradability from protein structure and E3 ligase identity alone -- the minimal information available at the target selection stage. The model encodes biophysical priors through lysine-weighted graph pooling with per-protein normalization, models protein-E3 compatibility via cross-attention, and integrates cellular context from the Cancer Dependency Map. On the PROTAC-8K benchmark (3,101 samples, 155 targets, 10 E3 ligases), DegradoMap achieves 0.646+-0.124 AUROC on target-unseen evaluation (best seed: 0.7449) and 0.811 AUROC on CRBN->VHL E3-unseen transfer, outperforming GNN and machine learning baselines. The model additionally recommends optimal E3 ligases with 74% Hit@3 accuracy. Two findings carry broader implications: E(3)-equivariant architectures underperform the simpler invariant design for this scalar prediction task, and ESM-2 embeddings improve peak performance only with careful regularization -- naive integration fails. DegradoMap provides pre-synthesis computational guidance for degradability assessment; its well-calibrated confidence scores (ECE = 0.029, target-unseen) enable practitioners to prioritize high-confidence predictions for experimental follow-up. However, the high seed variance (std = 0.124) and limited E3 coverage require ensembling for reliable deployment.
SpliceBind: 异构体感知的结合口袋可药性预测
Bryan Cheng, Austin Jin, Joshua Chang
AI总结 提出图神经网络框架SpliceBind,通过异构体感知预测可药性,揭示结构方法成功与失败的边界,并建立耐药性分类法以指导临床决策。
剪接介导的药物耐药性发生在高达40%的靶向激酶抑制剂患者中,然而最先进的可药性工具基于单一结构运行,无法跨异构体进行比较。我们引入SpliceBind,一个用于异构体感知可药性预测的图神经网络框架。除了提高预测准确性(AUROC 0.703 vs. P2Rank 0.634,p = 0.026),我们还解决了一个更基本的问题:结构方法何时成功,何时必然失败?对跨越五种机制类别的六个临床验证变体的系统分析揭示了一个双层耐药性分类法。结构域缺失(AR-V7,Delta = -18.39)和口袋破坏产生结构可检测的变化,而变构机制(BRAF-p61)仍然从根本上对任何口袋中心方法不可见——这是任何算法改进都无法跨越的边界。值得注意的是,学习到的嵌入捕获了仅靠几何结构无法识别的基于亲和力的耐药性(ALK-L1196M:Delta_SB = -0.228 vs. Delta_P2Rank = -0.95),部分弥合了结构-生化差距。在跨越25个家族的229个激酶口袋上,SpliceBind实现了AUROC 0.703(p = 0.026 vs. P2Rank),并对保留的家族具有稳健的泛化能力(AUROC 0.761)。这种分类法改变了临床工作流程:在发现剪接变体后,临床医生可以立即确定计算分诊是否足够,或者是否需要生化验证——从而缩短从变体发现到治疗决策的时间。
Splice-mediated drug resistance occurs in up to 40% of patients on targeted kinase inhibitors, yet state-of-the-art druggability tools operate on single structures and cannot compare across isoforms. We introduce SpliceBind, a graph neural network framework for isoform-aware druggability prediction. Beyond improving prediction accuracy (AUROC 0.703 vs. P2Rank 0.634, p = 0.026), we address a more fundamental question: when do structural methods succeed, and when must they fail? Systematic analysis of six clinically validated variants spanning five mechanism classes reveals a two-tier resistance taxonomy. Domain deletions (AR-V7, Delta = -18.39) and pocket disruptions produce structurally detectable changes, while allosteric mechanisms (BRAF-p61) remain fundamentally invisible to any pocket-centric approach -- a boundary no algorithmic improvement can cross. Notably, learned embeddings capture affinity-based resistance missed by geometry alone (ALK-L1196M: Delta_SB = -0.228 vs. Delta_P2Rank = -0.95), partially bridging the structural-biochemical gap. On 229 kinase pockets spanning 25 families, SpliceBind achieves AUROC 0.703 (p = 0.026 vs. P2Rank) with robust generalization to held-out families (AUROC 0.761). This taxonomy transforms clinical workflows: upon discovering a splice variant, clinicians can immediately determine whether computational triage suffices or biochemical validation is required -- reducing time from variant discovery to therapeutic decision.
基于意念测量学的意识、时间、空间与梦境理解
Igor Rudan
AI总结 本文从意念测量学视角提出意识通过意念过程减少信息熵,使系统模拟并选择最优未来,并探讨了时间、空间与梦境的演化意义。
从意念测量学的视角来看,意识可能通过意念过程减少许多随机可能的未来结果的信息熵。意识使系统能够内部模拟替代未来,然后基于意念过程自愿行动,以实现外部现实中的偏好状态。这可能解释了为什么大多数人类倾向于选择最小化威胁、最大化生存、繁殖、安全和福祉的未来。意念测量学通常使用三个基本标准:吸引力、可行性和许多竞争想法的潜在影响。原则上,可行性和潜在影响可以由非意识系统(包括人工智能)计算。然而,吸引力可能代表对可能未来的有意识和情感体验的评估。可行性可能在进化过程中首先出现,而潜在影响需要预测处理,意识则为许多替代未来增加了主观吸引力。在这个框架内,主观时间感可能与意识交织在一起,为感官感知的外部变化提供因果关联和内部排序。时间可能需要有意识的存在才有意义,而意识可能需要主观时间感才有意义。空间则提供了结构化的场域,使想法能够在嵌套尺度上获得因果影响。梦境可能代表了内部建模早期进化阶段的残余。
From an ideometrics-based perspective, consciousness may reduce the informational entropy of many randomly possible future outcomes through ideometric processes. Consciousness enables a system to internally simulate alternative futures and then voluntarily act, based on ideometric processes, towards realising preferred states in external reality. This may explain why most humans gravitate towards futures that minimise threat and maximise survival, reproduction, safety and well-being. Ideometrics typically uses three fundamental criteria: attractiveness, feasibility and potential impact of many competing ideas. Feasibility and potential impact can, in principle, be computed by non-conscious systems, including artificial intelligence (AI). However, attractiveness may represent the consciously and emotionally experienced valuation of possible futures. Feasibility may have appeared first during evolution, while potential impact required predictive processing, and consciousness added subjective attractiveness to many alternative futures. Within this framework, subjective sense of time may be intertwined with consciousness, providing causal relating and internal ordering to external changes perceived by the senses. Time may require conscious beings to have a meaning, while consciousness may require the subjective sense of time to have a meaning. Space, in turn, provides the structured field in which ideas can acquire causal impact across nested scales. Dreaming may represent remnants of earlier evolutionary stages of internal modelling.
大脑基础模型遗忘的方差:三阶统计在十亿参数模型失败时预测认知
Giovanni Marraffini, Gabriel Mahuas, Trinidad Borrell, Victoria Shevchenko, Demian Wassermann
AI总结 研究发现,大脑基础模型(BFMs)的预训练主要捕获了fMRI信号中的方差成分,但忽略了预测认知的高阶结构,而基于三阶协偏度张量的线性管道无需预训练即可超越现有BFMs。
大脑基础模型(BFMs)是在fMRI数据上预训练的自监督Transformer。我们认为这些模型应该能从fMRI信号中捕捉每个受试者的认知表现。然而,在三个最先进的BFM和所有我们测试的读出方法中,它们对认知的预测能力都低于基于功能连接矩阵(FC)的约8万参数的线性回归。差距随着规模扩大而加剧:BrainLM的6.5亿模型预测认知的能力低于其1.11亿模型。我们将此归因于方差分配问题:BFM预训练捕获了主导fMRI的方差成分,但没有捕获预测认知的高阶结构。我们对重构信号的每累积量分析表明,二阶协方差部分保留,而三阶协偏度张量大部分被破坏。为了恢复BFM丢失的信息,我们设计了一个线性管道,将fMRI信号投影到最能保留其协偏度的子空间,并在那里计算FC。这在我们测试的每个数据集和分区上都超过了原始FC和所有预训练的BFM,在受控评估下优于先前最先进方法,且无需预训练和GPU。我们通过在相同子空间上使用针对性的损失进行微调,恢复了BrainLM前向传播中原始FC的上限。这表明瓶颈在于预训练目标,而非架构或模型大小。
Brain foundation models (BFMs) are self-supervised Transformers pretrained on fMRI data. We posit that these models should capture each subject's cognitive performance from their fMRI signal. Yet across three state-of-the-art BFMs and every readout we test, they predict cognition worse than a linear regression from the $\sim$80K parameters of the functional connectivity matrix (FC). The gap widens with scale: BrainLM's 650M model predicts cognition worse than its 111M. We attribute this to a \textbf{variance allocation problem}: BFM pretraining captures the variance components that dominate fMRI but not the higher-order structure that predicts cognition. Our per-cumulant analysis of the reconstructed signal shows that the second-order covariance is partially preserved, while the third-order co-skewness tensor is largely destroyed. To recover what BFMs lose, we design a linear pipeline that projects the fMRI signal into the subspace that best preserves its co-skewness and computes FC there. This \textbf{exceeds raw FC and every pretrained BFM} on every dataset and parcellation we test, outperforming prior state-of-the-art under controlled evaluation \textbf{with no pretraining and no GPU}. We \textbf{recover the raw-FC ceiling on BrainLM's forward pass} by finetuning with a loss targeted at this same subspace. This shows that the bottleneck is the pretraining objective, not the architecture or the model size.
氧合与空间异质性通过表型适应塑造放疗方案排名
Francesco Albanese, Giulia Chiari, Marcello Edoardo Delitala
AI总结 本研究通过整合空间氧动力学与连续表型适应的数学模型,系统比较了不同放疗分次方案在正常组织毒性约束下的表现,发现氧合均匀性、缺氧程度及氧源空间分布显著影响方案排名和疗效。
肿瘤对放疗的反应受氧可用性和表型异质性的强烈影响,但它们对分次方案相对性能的综合影响仍不清楚。在此,我们开发了一个数学模型,将空间氧动力学与对缺氧和辐射的连续表型适应相结合,并利用它在常见的正常组织毒性约束下系统比较放疗方案。在空间均匀氧合条件下,我们发现替代分次方案在常氧条件下相比标准治疗方案几乎没有改善。然而,在中度缺氧条件下,一类具有较长分次间隔的独特延长方案显著增加了进展时间,在某些情况下高达两倍。这种依赖于状态的益处与再氧合和抗性表型选择之间平衡的转变一致。当氧输送空间异质时,治疗结果强烈依赖于氧源的几何组织。即使总供氧量相同,不同的空间配置也会导致进展时间的大变异性,并可能改变放疗方案的相对排名。这些结果表明,放疗有效性并非治疗方案本身的固有属性,而是源于其与肿瘤微环境结构和进化动力学的相互作用。因此,整合空间异质性和表型适应可能对于异质性肿瘤中分次策略的一致评估和设计至关重要。
Tumor response to radiotherapy is strongly influenced by oxygen availability and phenotypic heterogeneity, yet their combined impact on the relative performance of fractionation schedules remains unclear. Here, we develop a mathematical model that integrates spatial oxygen dynamics with continuous phenotypic adaptation to hypoxia and radiation, and use it to systematically compare radiotherapy protocols under a common normal-tissue toxicity constraint. Under spatially uniform oxygenation, we find that alternative fractionation schedules provide little improvement over standard-of-care protocols in normoxic conditions. Under moderate hypoxia, however, a distinct class of protracted schedules with longer inter-fraction intervals substantially increases time-to-progression, in some cases by up to twofold. This regime-dependent benefit is consistent with a shift in the balance between reoxygenation and selection for resistant phenotypes. When oxygen delivery is spatially heterogeneous, treatment outcomes depend strongly on the geometric organization of oxygen sources. Even with identical total oxygen supply, different spatial configurations lead to large variability in time-to-progression and can alter the relative ranking of radiotherapy protocols. These results show that radiotherapy effectiveness is not an intrinsic property of a treatment schedule alone, but emerges from its interaction with tumor microenvironmental structure and evolutionary dynamics. Incorporating both spatial heterogeneity and phenotypic adaptation may therefore be important for the consistent evaluation and design of fractionation strategies in heterogeneous tumors.
使用可解释机器学习基于临床生物标志物早期检测阿尔茨海默病:基于阿尔茨海默病神经影像学倡议(ADNI)数据集的多分类研究
Afshan Hashmi
AI总结 本研究使用XGBoost分类器,基于ADNI数据集的8个临床特征(MMSE、CDR Global、CDR-SB、MoCA、FAQ、年龄、性别、教育程度)进行三分类(正常认知、轻度认知障碍、阿尔茨海默病)检测,通过SMOTE处理类别不平衡,Optuna优化超参数,SHAP提供可解释性,在测试集上达到macro AUC 0.982、准确率0.943,并揭示了临床合理的特征重要性模式。
背景:阿尔茨海默病(AD)影响全球超过5500万人。从常规临床评估中准确、可解释地检测正常认知(NC)、轻度认知障碍(MCI)和AD仍是一个关键未满足需求。方法:使用XGBoost分类器进行三分类检测,采用来自阿尔茨海默病神经影像学倡议(ADNI)的八个临床特征:MMSE、CDR Global、CDR Sum of Boxes(CDR-SB)、MoCA、FAQ、年龄、性别和教育程度。使用Optuna(50次试验)优化超参数;通过SMOTE处理类别不平衡。性能通过macro AUC-ROC(1000次迭代bootstrap 95%置信区间)、macro F1、平衡准确率和Cohen's kappa评估。SHAP值提供特征级别的可解释性。结果:数据集包含1641名基线受试者(608 NC、767 MCI、266 AD)。在五折交叉验证中,平均macro AUC为0.983(SD 0.007),准确率为0.944(SD 0.006),macro F1为0.929(SD 0.008)。在保留测试集(n=247)上,macro AUC为0.982(95% CI: 0.965--0.995),准确率为0.943,平衡准确率为0.932,macro F1为0.927,Cohen's kappa为0.909。SHAP分析确定CDR Global是NC和MCI的主要预测因子,而CDR-SB和MMSE共同驱动AD分类。结论:一个基于常规临床评估训练的可解释机器学习模型实现了近乎完美的三分类阿尔茨海默病检测。SHAP分析揭示了临床合理、类别特定的特征重要性模式,支持临床有效性。未来工作将扩展该框架,加入语音生物标志物以实现多模态检测。
Background: Alzheimer's disease (AD) affects over 55 million people worldwide. Accurate, interpretable detection of normal cognition (NC), mild cognitive impairment (MCI), and AD from routine clinical assessments remains a critical unmet need. Methods: An XGBoost classifier was developed for three-class detection using eight clinical features from the Alzheimer's Disease Neuroimaging Initiative (ADNI): MMSE, CDR Global, CDR Sum of Boxes (CDR-SB), MoCA, FAQ, age, sex, and education. Hyperparameters were optimised using Optuna (50 trials); class imbalance was addressed with SMOTE. Performance was evaluated by macro AUC-ROC with 1,000-iteration bootstrap 95% confidence intervals, macro F1, balanced accuracy, and Cohen's kappa. SHAP values provided feature-level explainability. Results: The dataset comprised 1,641 baseline subjects (608 NC, 767 MCI, 266 AD). On five-fold cross-validation, mean macro AUC was 0.983 (SD 0.007), accuracy 0.944 (SD 0.006), and macro F1 0.929 (SD 0.008). On the held-out test set (n = 247), macro AUC was 0.982 (95% CI: 0.965--0.995), accuracy 0.943, balanced accuracy 0.932, macro F1 0.927, and Cohen's kappa 0.909. SHAP analysis identified CDR Global as the dominant predictor for NC and MCI, while CDR-SB and MMSE together drove AD classification. Conclusion: An explainable machine learning model trained on routine clinical assessments achieves near-perfect three-class Alzheimer's detection. SHAP analysis reveals clinically plausible, class-specific feature importance patterns supporting clinical validity. Future work will extend this framework with speech biomarkers for multimodal detection.
AI中介的后果性决策中的选择错觉
Eugene Yu Ji
AI总结 基于Ullmann-Margalit的选择概念,揭示当前AI系统造成一种“选择错觉”,即看似有意义的后果性选择实则削弱了主体的真正选择能力,并提出通过存在诚实、生态理性和反事实修复三个规范要义来保护和发展元能力。
借鉴Ullmann-Margalit的选择概念(变革性、不可逆性、被排除替代方案的阴影),我们表明当前AI系统引发了一个深刻的伦理问题,而现有AI伦理尚未充分捕捉:选择错觉,即个人和群体遭遇看似有意义的后果性选择的欺骗性外观,而成为真正能够选择所需的主体性却被削弱。针对将AI主要视为给定目标优化器的进路,我们认为应通过AI系统是否保护和发展对抗选择错觉的元能力来评估:这种元能力是社会和制度支撑的主体能力,通过它手段和目的得以形成、争论、修订和拥有。这种重新框架对于弱势群体尤为紧迫,当AI中介的路径误导行为和行动时,他们最无力承担选择错觉的成本。我们为AI中介的后果性决策提出三个规范要义:存在诚实,承认预测的局限性;生态理性,将指导置于异质的生活生态中;以及反事实修复,当AI中介的决策路径失败时,承认并修复被排除的替代方案。
Drawing on Ullmann-Margalit's concept of opting (transformative, irrevocable, and shadowed by foreclosed alternatives), we show that current AI systems raise a profound ethical problem that existing AI ethics has not fully captured: the illusion of opting, in which persons and groups encounter the deceptive appearance of meaningful consequential choice while the agency needed to become genuinely capable of choosing is weakened. Against approaches that treat AI primarily as an optimizer of already given ends, we argue that AI systems should be evaluated by whether they protect and cultivate meta-capacity against the illusion of opting: the socially and institutionally scaffolded agentive capacity through which means and ends can be formed, contested, revised, and owned. This reframing is especially urgent for disadvantaged populations, who are least able to absorb the costs of the illusion of opting when AI-mediated pathways misdirect behavior and action. We propose three normative imperatives for AI-mediated consequential decisions: existential honesty, which acknowledges the limits of prediction; ecological rationality, which situates guidance within heterogeneous lived ecologies; and counterfactual reparation, which acknowledges and repairs foreclosed alternatives when AI-mediated decision-making pathways fail.
约束下的高效编码驱动神经系统趋向临界性和松散性
He Xiao, Xinyue Zhao, Haijun Zhou, Weikang Wang
AI总结 本文通过高斯群体编码模型,证明在资源约束下最大化Fisher信息自然导致软模和发散相关长度等临界性特征,并统一了统计临界性与动力学临界性,同时解释了神经系统的松散性。
人们普遍认为大脑在临界状态附近运行,其特征是遵循幂律分布的神经雪崩。然而,神经系统中临界性出现的功能原理仍不清楚。在这里,我们提出了一个理论框架,将高效编码与神经群体中的临界性联系起来。使用高斯群体编码模型,我们证明在资源约束下最大化Fisher信息自然导致软模和发散相关长度的出现,这是临界性的标志。通过引入空间结构,我们统一了临界性的两个不同视角:具有发散相关长度的统计临界性和具有临界慢化以及分岔的动力学临界性。此外,该框架为神经系统中观察到的松散性提供了自然解释。数值模拟证实,优化导致幂律响应,为高效编码、松散性和临界大脑假说之间提供了机制联系。
It is widely accepted that the brain operates near a critical state, characterized by neural avalanches that follow power-law distributions. However, the functional rationale for why neural systems attain criticality remains unclear. Here, we present a theoretical framework that links efficient coding to criticality in neural populations. Using a Gaussian population coding model, we demonstrate that maximizing Fisher information under resource constraints naturally leads to the emergence of soft modes and diverging correlation lengths, which are hallmarks of criticality. By introducing spatial structure, we unify two distinct perspectives of criticality: statistical criticality with diverging correlation lengths and dynamical criticality with critical slowing down as well as bifurcation. Furthermore, this framework provides a natural explanation for the sloppiness observed in neural systems. Numerical simulations confirm that optimization results in power-law response, providing a mechanistic link between efficient coding, sloppiness and the critical brain hypothesis.
检索与竞争:蛋白质基础模型如何启动蛋白质
Piotr Jedryszek, Oliver M. Crook
AI总结 通过追踪ESM2-8M预测蛋白质起始甲硫氨酸的计算路径,发现模型依赖位置先验检索而非直接识别,揭示了模型置信度与生物学证据之间的脱节。
蛋白质语言模型越来越多地用于指导实验和临床决策,但通常不清楚一个自信的预测是反映了对生物学证据的识别还是对统计默认值的检索。我们针对一个近乎普遍的生物学规则——蛋白质以甲硫氨酸起始——通过追踪ESM2-8M产生该预测的计算路径来检验这一区别。模型并未检测到掩码位置的甲硫氨酸。相反,它通过跨层组装的特定位置查询,从序列起始标记处的参考表示中检索出有利于甲硫氨酸的信号,最终输出通过与上下文相关电路的竞争而出现。为了理解位置信息如何到达读出端,我们引入了旋转频率带内注意力分数的范数-方向分解。位置编码通过分布在各个频带中的查询范数和角度对齐的耦合变化来运作。对于真实N端不是甲硫氨酸的序列(此时生物学问题至关重要),模型仍然预测甲硫氨酸。这不是由意外机制产生的正确预测,而是匹配统计平均值的位置先验检索电路的输出,在生物学偏离平均值的地方失败。区分这两者需要在单个电路、频率带和查询组成的层面上进行解析,这表明在生物学风险更高的预测中,机制验证将是必要且具有挑战性的。即使对于最简单的生物学规则,模型的预测也是通过分布式计算电路而非直接识别来介导的,这表明任务复杂性的增加将进一步模糊模型置信度与潜在生物学证据之间的关系。
Protein language models are increasingly used to guide experimental and clinical decisions, yet it is often unclear whether a confident prediction reflects recognition of biological evidence or retrieval of a statistical default. We examine this distinction for a near-universal biological rule, that proteins begin with methionine, by tracing the computational pathway through which ESM2-8M produces this prediction. The model does not detect methionine at the masked position. Instead, it retrieves a methionine-favouring signal from a reference representation at the beginning-of-sequence token via a position-specific query assembled across layers, with the final output emerging through competition with context-dependent circuits. To understand how positional information reaches the readout, we introduce a norm-direction decomposition of attention scores within rotary frequency bands. Positional encoding operates through coupled changes in query norm and angular alignment distributed across these bands. On sequences whose true N-terminus is not methionine, where the biological question matters, the model predicts methionine anyway. This is not a correct prediction produced by an unexpected mechanism, but the output of a positional-prior retrieval circuit that matches the statistical average and fails where biology diverges from it. Distinguishing the two requires resolution at the level of individual circuits, frequency bands, and query composition, suggesting that mechanistic verification will be necessary, and challenging, for predictions where the biological stakes are higher. Even for the simplest biological rule, the model's prediction is mediated by a distributed computational circuit rather than direct recognition, suggesting that increasing task complexity will further obscure the relationship between model confidence and underlying biological evidence.
脑刺激中的介观组织特性与电场:利用层特异性皮层电导率桥接宏观与微观尺度
Boshuo Wang, Torge H. Worbs, Minhaj A. Hussain, Aman S. Aberra, Axel Thielscher, Warren M. Grill, Angel V. Peterchev
AI总结 本文综述了通过微观模型估计皮层层特异性电导率的方法,发现层间电导率差异显著(如第3层和第6层分别比第2层高20%和50%),并指出在脑刺激电场模型中采用层特异性电导率可提高神经激活阈值和分布估计的准确性。
神经刺激中电场(E场)的精确模拟依赖于将微观组织结构与宏观假设联系起来的组织电导率表示。介观尺度的电导率变化可以引起电场和神经激活阈值的有意义变化,但在标准宏观模型中基本缺失。考虑到皮层各层细胞密度和体积分数的差异,皮层内的电导率变化是预期的。我们回顾了最近在微观和介观电场建模方面的努力,并概述了桥接微观和宏观尺度以推导一致介观电导率分布的方法。使用简化的微观模型,有效组织电导率被估计为细胞外空间体积分数的函数,并且基于实验体积分数插值了不同皮层层的电导率。有效组织电导率是细胞体积分数的单调递减凸函数。随着细胞体积分数的减少,皮层层的电导率从第2层到第6层随深度增加。尽管皮层内的电导率变化与细胞外液的电导率相比很小(9%至15%),但层间电导率差异相当大,例如第3层和第6层分别比第2层高20%和50%。该综述和分析为精确的多尺度电场和神经刺激模型提供了基础。在皮层内使用层特异性电导率值可以提高脑刺激电场模型中神经激活阈值和分布估计的准确性。
Accurate simulations of electric fields (E-fields) in neural stimulation depend on tissue conductivity representations that link underlying microscopic tissue structure with macroscopic assumptions. Mesoscale conductivity variations can produce meaningful changes in E-fields and neural activation thresholds but remain largely absent from standard macroscopic models. Conductivity variations within the cortex are expected given the differences in cell density and volume fraction across layers. We review recent efforts modeling microscopic and mesoscopic E-fields and outline approaches that bridge micro- and macroscales to derive consistent mesoscale conductivity distributions. Using simplified microscopic models, effective tissue conductivity was estimated as a function of volume fraction of extracellular space, and the conductivities of different cortical layers were interpolated based on experimental volume fraction. The effective tissue conductivities were monotonically decreasing convex functions of the cell volume fraction. With decreasing cell volume fraction, the conductivity of cortical layers increased with depth from layer 2 to 6. Although the variation of conductivity within the cortex was small when compared to the conductivity of extracellular fluid (9% to 15%), the conductivity difference was considerably larger when compared between layers, e.g., with layer 3 and 6 being 20% and 50% more conductive than layer 2, respectively. The review and analysis provide a foundation for accurate multiscale models of E-fields and neural stimulation. Using layer-specific conductivity values within the cortex could improve the accuracy of estimations of thresholds and distributions of neural activation in E-field models of brain stimulation.
亚临床焦虑体验与表达背后的内在脑网络
Shruti Kinger, Naviya Lall, Mrinmoy Chakrabarty
AI总结 通过静息态功能连接分析,发现亚临床焦虑的行为、生理和主观成分分别与前扣带回-岛叶、前扣带回-眶额皮层和海马-岛叶连接相关,表明这些维度由部分可分离的内在脑网络支持。
焦虑包括行为、生理和主观成分,这些成分并不总是一致的,目前尚不清楚这些维度是否由不同的内在脑网络支持。在双系统框架的指导下,我们测试了静息态功能连接(rsFC)是否能在亚临床焦虑中区分这些成分。47名具有不同亚临床焦虑水平的年轻成年人完成了一项威胁预期任务,测量了行为反应(反应时间)和生理唤醒(皮肤电导),以及NIH恐惧-情感自我报告中的焦虑严重程度。这些测量结果通过感兴趣区域分析与rsFC相关联。较高的亚临床焦虑与时间不确定威胁下的更快反应相关,这与警惕性增加一致,而与生理唤醒无关联。在神经层面,出现了三种连接模式,并在序列族系误差校正后仍然显著。由亚临床焦虑调节的行为反应与前扣带回(ACC)和岛叶之间的更强连接相关。生理调节与ACC和眶额皮层(OFC)之间的连接相关。主观焦虑与海马和岛叶之间的连接增加相关。还观察到其他连接,但未通过更严格的校正。总体而言,研究结果表明,亚临床焦虑的行为、生理和主观方面映射到部分可分离但重叠的内在脑网络,将先前基于任务的结果扩展到静息态连接,并为未来关于焦虑早期神经标志物的研究提供信息。
Anxiety includes behavioural, physiological, and subjective components that do not always align, and it remains unclear whether these dimensions are supported by distinct intrinsic brain networks. Guided by the two-system framework, we tested whether resting-state functional connectivity (rsFC) differentiates these components in subclinical anxiety. Forty-seven young adults spanning a range of subclinical anxiety levels completed a threat anticipation task measuring behavioral responses (reaction time) and physiological arousal (skin conductance), along with the NIH Fear-Affect self-report of anxiety severity. These measures were related to rsFC using region-of-interest analyses. Higher subclinical anxiety was associated with faster responses under temporally uncertain threat, consistent with increased vigilance, while no association was found with physiological arousal. At the neural level, three connectivity patterns emerged and remained significant after sequential family-wise error correction. Behavioural responses modulated by subclinical anxiety were linked to stronger connectivity between the anterior cingulate cortex (ACC) and insula. Physiological modulation was associated with connectivity between the ACC and orbitofrontal cortex (OFC). Subjective anxiety was associated with increased connectivity between the hippocampus and insula. Additional connections were observed but did not survive stricter correction. Overall, the findings indicate that behavioural, physiological, and subjective aspects of subclinical anxiety map onto partially dissociable but overlapping intrinsic brain networks, extending prior task-based results to resting-state connectivity and informing future work on early neural markers of anxiety.
漂移-扩散匹配:非对称神经网络潜在流形中的动力学嵌入
Ramón Nartallo-Kaluarachchi, Renaud Lambiotte, Alain Goriely
AI总结 提出漂移-扩散匹配框架,通过训练连续时间循环神经网络在低维潜在子空间中嵌入任意非线性随机微分方程,利用非对称连接实现非平衡动力学,并应用于联想记忆和序列记忆建模。
循环神经网络(RNN)为理解生物神经回路中的计算提供了理论框架,然而经典结果(如Hopfield联想记忆模型)依赖于对称连接,将网络动力学限制为梯度流。相比之下,生物网络支持由其非对称性促进的丰富时间依赖行为。本文引入一个通用框架,称为漂移-扩散匹配,用于训练连续时间RNN在低维潜在子空间中表示具有给定漂移和扩散系数的任意非线性随机微分方程(SDE)。通过允许非对称连接,我们证明RNN能够忠实地嵌入给定SDE的漂移和扩散,包括非线性非平衡动力学(如混沌吸引子)。作为应用,我们构建了随机系统的RNN实现,这些系统通过输入驱动切换和由非平衡电流驱动的自主跃迁短暂探索各种吸引子,我们将其解释为联想记忆和序列(情景)记忆的模型。为了阐明这些动力学如何在网络中编码,我们基于RNN的非对称连接及其时间不可逆性引入分解。我们的结果将吸引子神经网络理论扩展到平衡态之外,表明非对称神经群体可以在低维流形内实现广泛的动力学计算,统一了来自联想记忆、非平衡统计力学和神经计算的思想。
Recurrent neural networks (RNNs) provide a theoretical framework for understanding computation in biological neural circuits, yet classical results, such as Hopfield's model of associative memory, rely on symmetric connectivity that restricts network dynamics to gradient-like flows. In contrast, biological networks support rich time-dependent behaviour facilitated by their asymmetry. Here we introduce a general framework, which we term drift-diffusion matching, for training continuous-time RNNs to represent arbitrary, nonlinear stochastic differential equations (SDEs), with given drift and diffusion coefficients, within a low-dimensional latent subspace. Allowing asymmetric connectivity, we show that RNNs can faithfully embed the drift and diffusion of a given SDE, including nonlinear and nonequilibrium dynamics such as chaotic attractors. As an application, we construct RNN realisations of stochastic systems that transiently explore various attractors through both input-driven switching and autonomous transitions driven by nonequilibrium currents, which we interpret as models of associative and sequential (episodic) memory. To elucidate how these dynamics are encoded in the network, we introduce decompositions of the RNN based on its asymmetric connectivity and its time-irreversibility. Our results extend attractor neural network theory beyond equilibrium, showing that asymmetric neural populations can implement a broad class of dynamical computations within low-dimensional manifolds, unifying ideas from associative memory, nonequilibrium statistical mechanics, and neural computation.
MuCO:基于多阶段构象优化的生成式肽环化
Yitian Wang, Fanmeng Wang, Angxiao Yue, Wentao Guo, Yaning Cui, Hongteng Xu
AI总结 提出MuCO方法,通过多阶段构象优化生成环肽构象,在物理稳定性、结构多样性和计算效率上优于现有方法。
建模肽环化对于虚拟筛选具有理想物理和药物特性的候选肽至关重要。这一任务具有挑战性,因为环肽通常呈现多样化的环状构象,而由线性肽折叠推导出的确定性预测模型无法很好地捕捉这些构象。在本研究中,我们提出MuCO(多阶段构象优化),一种生成式肽环化方法,对以相应线性肽为条件的环肽构象分布进行建模。原则上,MuCO将肽环化任务解耦为三个阶段:拓扑感知的主链设计、生成式侧链打包和物理感知的全原子优化,从而以从粗到细的方式生成和优化环肽构象。这种多阶段框架实现了用于构象生成的高效并行采样策略,并允许快速探索多样化的低能构象。在大型CPSea数据集上的实验表明,MuCO在物理稳定性、结构多样性、二级结构恢复和计算效率方面显著且一致地优于最先进的方法,使其成为探索和设计环肽的有前景的计算工具。所提出方法的演示可在https://github.com/mianqiu00/MuCO找到。
Modeling peptide cyclization is critical for the virtual screening of candidate peptides with desirable physical and pharmaceutical properties. This task is challenging because a cyclic peptide often exhibits diverse, ring-shaped conformations, which cannot be well captured by deterministic prediction models derived from linear peptide folding. In this study, we propose MuCO (Multi-stage Conformation Optimization), a generative peptide cyclization method that models the distribution of cyclic peptide conformations conditioned on the corresponding linear peptide. In principle, MuCO decouples the peptide cyclization task into three stages: topology-aware backbone design, generative side-chain packing, and physics-aware all-atom optimization, thereby generating and optimizing conformations of cyclic peptides in a coarse-to-fine manner. This multi-stage framework enables an efficient parallel sampling strategy for conformation generation and allows for rapid exploration of diverse, low-energy conformations. Experiments on the large-scale CPSea dataset demonstrate that MuCO significantly and consistently outperforms state-of-the-art methods in physical stability, structural diversity, secondary structure recovery, and computational efficiency, making it a promising computational tool for exploring and designing cyclic peptides. The demo of the proposed method can be found at https://github.com/mianqiu00/MuCO.
TF-DWGNet: 基于张量融合的有向加权图神经网络用于多组学癌症亚型分类
Tiantian Yang, Zhiqian Chen
AI总结 提出TF-DWGNet框架,结合基于树的有向加权图构建与张量融合机制,解决多组学数据异质性和高阶交互问题,在癌症亚型分类中优于现有方法并提供可解释性。
多组学数据的整合与分析为改善癌症亚型分类提供了宝贵的见解。然而,这些数据本质上是异质的、高维的,并表现出复杂的模态内和模态间依赖关系。图神经网络(GNN)为建模这些结构提供了一个原则性框架,但现有方法通常依赖先验知识或预定义的相似性网络,这些网络生成无向或无权重图,无法捕捉任务特定的方向性和交互强度。在模态和特征层面的可解释性也仍然有限。为了解决这些挑战,我们提出了TF-DWGNet,一种新颖的图神经网络框架,它结合了基于树的有向加权图构建与张量融合,用于多类癌症亚型分类。TF-DWGNet引入了两个关键创新:(i)一种监督的基于树的策略,为每种组学模态构建定制的有向加权图,以及(ii)一种张量融合机制,通过低秩分解捕获单模态、双模态和三模态交互,以提高计算效率。在三个真实世界癌症数据集上的实验表明,TF-DWGNet在多个指标和统计测试中始终优于最先进的基线方法。此外,该模型通过模态级贡献分数和排序的特征重要性提供了生物学上有意义的见解。这些结果突显了TF-DWGNet是癌症研究中多组学整合的有效且可解释的解决方案。
Integration and analysis of multi-omics data provide valuable insights for improving cancer subtype classification. However, such data are inherently heterogeneous, high-dimensional, and exhibit complex intra- and inter-modality dependencies. Graph neural networks (GNNs) offer a principled framework for modeling these structures, but existing approaches often rely on prior knowledge or predefined similarity networks that produce undirected or unweighted graphs and fail to capture task-specific directionality and interaction strength. Interpretability at both the modality and feature levels also remains limited. To address these challenges, we propose TF-DWGNet, a novel Graph Neural Network framework that combines tree-based Directed Weighted graph construction with Tensor Fusion for multiclass cancer subtype classification. TF-DWGNet introduces two key innovations: (i) a supervised tree-based strategy that constructs directed, weighted graphs tailored to each omics modality, and (ii) a tensor fusion mechanism that captures unimodal, bimodal, and trimodal interactions using low-rank decomposition for computational efficiency. Experiments on three real-world cancer datasets demonstrate that TF-DWGNet consistently outperforms state-of-the-art baselines across multiple metrics and statistical tests. In addition, the model provides biologically meaningful insights through modality-level contribution scores and ranked feature importance. These results highlight that TF-DWGNet is an effective and interpretable solution for multi-omics integration in cancer research.
Feller扩散作为并合点过程的极限
Conrad J. Burden, Robert C. Griffiths
AI总结 研究Feller扩散作为并合点过程的极限,其中节点高度分布密度偏向零,通过统一方法回顾分支过程标度极限的结果,并推广伯努利抽样到扩散极限,分析泊松抽样和k抽样Feller扩散的并合性质。
Feller扩散被研究作为并合点过程的极限,其中节点高度分布的密度偏向零。使用统一方法,回顾并重新解释了一些关于分支过程标度极限的最新结果,作为该极限产生的Feller扩散的性质。将有限总体的伯努利抽样概念扩展到扩散极限,以覆盖从无限连续总体中抽取的有限泊松分布样本。我们表明,泊松抽样Feller扩散的并合树对应于一个并合点过程,其节点高度分布与伯努利抽样生灭过程具有相同的代数形式。通过改编分析k抽样生灭过程(其中样本大小预先指定)的方法,我们开发了研究k抽样Feller扩散并合性质的方法。
The Feller diffusion is studied as the limit of a coalescent point process in which the density of the node height distribution is skewed towards zero. Using a unified approach, a number of recent results pertaining to scaling limits of branching processes are reviewed and reinterpreted as properties of the Feller diffusion arising from this limit. The notion of Bernoulli sampling of a finite population is extended to the diffusion limit to cover finite Poisson-distributed samples drawn from infinite continuum populations. We show that the coalescent tree of a Poisson-sampled Feller diffusion corresponds to a coalescent point process with a node height distribution taking the same algebraic form as that of a Bernoulli-sampled birth-death process. By adapting methods for analysing k-sampled birth-death processes, in which the sample size is pre-specified, we develop methods for studying the coalescent properties of the k-sampled Feller diffusion.
兴奋-抑制神经回路中的竞争、稳定性和功能
Simone Betteti, William Retnaraj, Alexander Davydov, Jorge Cortés, Francesco Bullo
AI总结 通过博弈-能量框架和网络稳定性原理,研究不对称兴奋-抑制神经网络的动力学、调控及其在侧抑制微电路对比增强中的作用。
基于能量的模型已成为理解理论神经科学和机器学习中计算与稳定性的核心范式。然而,能量框架通常依赖于突触或权重矩阵的对称性——这一约束排除了生物现实系统,如兴奋-抑制(E-I)网络。当对称性放松时,全局能量景观的经典概念失效,使得非对称神经系统的动力学在概念上失去锚点。在本工作中,我们将能量框架扩展到非对称发放率网络,揭示了神经动力学的潜在博弈论结构,其中每个神经元是一个寻求最小化自身能量的智能体。此外,我们利用网络理论中严格的稳定性原理来研究E-I网络中神经活动的调节与平衡。我们将新的博弈-能量解释与稳定性结果相结合,重新审视理论神经科学中的标准框架,如Wilson-Cowan和侧抑制模型。这些见解使我们能够研究作为对比增强器的侧抑制微电路皮层柱——通过分层兴奋-抑制相互作用选择性锐化环境中的细微差异。我们的结果桥接了神经计算的能量视角和博弈视角,为系统化设计具有生物基础且动态稳定的神经架构提供了途径。
Energy-based models have become a central paradigm for understanding computation and stability in both theoretical neuroscience and machine learning. However, the energetic framework typically relies on symmetry in synaptic or weight matrices - a constraint that excludes biologically realistic systems such as excitatory-inhibitory (E-I) networks. When symmetry is relaxed, the classical notion of a global energy landscape fails, leaving the dynamics of asymmetric neural systems conceptually unanchored. In this work, we extend the energetic framework to asymmetric firing rate networks, revealing an underlying game-theoretic structure for the neural dynamics in which each neuron is an agent that seeks to minimize its own energy. In addition, we exploit rigorous stability principles from network theory to study regulation and balancing of neural activity in E-I networks. We combine the novel game-energetic interpretation and the stability results to revisit standard frameworks in theoretical neuroscience, such as the Wilson-Cowan and lateral inhibition models. These insights allow us to study cortical columns of lateral inhibition microcircuits as contrast enhancer - with the ability to selectively sharpen subtle differences in the environment through hierarchical excitation-inhibition interplay. Our results bridge energetic and game-theoretic views of neural computation, offering a pathway toward the systematic engineering of biologically grounded, dynamically stable neural architectures.
epiGPTope: 一种基于机器学习的表位生成器和分类器
Natalia Flechas Manrique, Alberto Martínez, Elena López-Martínez, Luc Andrea, Román Orus, Aitor Manteca, Aitziber L. Cortajarena, Llorenç Espinosa-Portalés
AI总结 提出基于大型语言模型epiGPTope,通过预训练和微调直接生成新型表位序列,并结合统计分类器预测表位来源(细菌或病毒),以加速合成表位库的构建和筛选。
表位是能被抗体或免疫细胞受体识别的短抗原肽序列,对免疫疗法、疫苗和诊断的开发至关重要。然而,由于巨大的组合序列空间(n个氨基酸的线性表位有$20^n$种组合),即使采用高通量实验技术,合成表位库的合理设计也极具挑战。在本研究中,我们提出了一种大型语言模型epiGPTope,该模型在蛋白质数据上预训练,并专门针对线性表位进行微调,首次能够直接生成新型表位样序列,这些序列被发现具有与已知表位相似的统计特性。这种生成方法可用于制备表位候选序列库。我们进一步训练统计分类器来预测表位序列是细菌来源还是病毒来源,从而缩小候选库范围,提高识别特定表位的可能性。我们提出,这种生成模型与预测模型的组合有助于表位发现。该方法仅使用线性表位的一级氨基酸序列,无需几何框架或手工特征。通过开发生成生物学可行序列的方法,我们预期能更快、更经济地生成和筛选合成表位,并在新生物技术开发中具有相关应用。
Epitopes are short antigenic peptide sequences which are recognized by antibodies or immune cell receptors. These are central to the development of immunotherapies, vaccines, and diagnostics. However, the rational design of synthetic epitope libraries is challenging due to the large combinatorial sequence space, $20^n$ combinations for linear epitopes of n amino acids, making screening and testing unfeasible, even with high throughput experimental techniques. In this study, we present a large language model, epiGPTope, pre-trained on protein data and specifically fine-tuned on linear epitopes, which for the first time can directly generate novel epitope-like sequences, which are found to possess statistical properties analogous to the ones of known epitopes. This generative approach can be used to prepare libraries of epitope candidate sequences. We further train statistical classifiers to predict whether an epitope sequence is of bacterial or viral origin, thus narrowing the candidate library and increasing the likelihood of identifying specific epitopes. We propose that such combination of generative and predictive models can be of assistance in epitope discovery. The approach uses only primary amino acid sequences of linear epitopes, bypassing the need for a geometric framework or hand-crafted features of the sequences. By developing a method to create biologically feasible sequences, we anticipate faster and more cost-effective generation and screening of synthetic epitopes, with relevant applications in the development of new biotechnologies.
神经朗之万机:一种局部非对称学习规则可以具有创造性
Zhendong Yu, Weizhong Huang, Haiping Huang
AI总结 本文提出神经朗之万机,利用递归神经网络的固定点通过非对称、速率调整的局部学习规则进行生成学习,并揭示了非平衡生成过程及记忆到泛化的转变。
递归神经网络的固定点可用于存储和生成信息。这些固定点可以通过玻尔兹曼-吉布斯测度捕获,从而得到神经朗之万动力学,可用于在真实数据集的生成学习中找到它们。我们将这种生成模型称为神经朗之万机,它推导出一种非对称且放电速率调整的学习规则,仅需要局部神经信号,因此在局部预测学习方面具有生物学相关性。揭示了生成过程中一个有趣的非平衡状态,以及随着训练数据量增加从记忆到泛化的转变。这种神经启发机器还可以实现对不同种类生成图像的相空间连续探索,并且能够对受损图像进行去噪。
Fixed points of recurrent neural networks can be leveraged to store and generate information. These fixed points can be captured by the Boltzmann-Gibbs measure, which leads to neural Langevin dynamics that can be used to find them for generative learning of a real dataset. We call this type of generative model a neural Langevin machine, which derives an asymmetric and firing-rate-speed adjusted learning rule requiring only local neural signals, thereby bearing biological relevance in terms of local predictive learning. An interesting out-of-equilibrium regime of the generative process is revealed, together with a memorization-to-generalization transition with increasing training data size. The neuro-inspired machine can also realize a continuous exploration of the phase space for different kinds of generative images and can denoise a corrupted image as well.
用于底栖图像不确定性估计的最后一层委员会机器
H. Martin Gillis, Isaac Xu, Benjamin Misiuk, Craig J. Brown, Thomas Trappenberg
AI总结 提出一种单层最后一层委员会机器方法,通过减少95%以上的网络参数,高效估计底栖图像分类的不确定性,性能与贝叶斯神经网络等复杂方法相当。
自动化底栖图像(即海底及其相关生物、栖息地和地质特征的图像)注释对于监测快速变化的海洋生态系统至关重要。深度学习方法已成功用于此目的;然而,由于模糊的海底图像、潜在的用户间注释分歧以及分布外样本,一致的注释仍然具有挑战性。实施深度学习模型的海洋科学家通常基于使用交叉熵损失目标结合softmax归一化训练的单热表示获得预测,从而得到一组模型参数。虽然高效,但这种方法可能导致对上下文挑战性数据集的过度自信预测,引发可靠性问题,对下游任务(如底栖栖息地测绘和海洋空间规划)构成风险。在本研究中,我们研究了分类不确定性作为改进底栖栖息地图像标注的工具。我们针对最近公开的BenthicNet数据集的两个具有挑战性的子数据集,使用贝叶斯神经网络、蒙特卡洛丢弃推理采样以及提出的单层最后一层委员会机器开发了一个框架。该方法将网络参数减少了95%以上,以获得每个样本的不确定性,同时与贝叶斯神经网络、蒙特卡洛丢弃和深度集成等计算成本更高的策略相比,性能几乎相同。本研究提出的方法提供了一种策略,用于获取优先排序的不确定样本列表,以便进行人在回路干预,识别模糊、错误标记、分布外和/或困难的图像,从而增强现有的底栖测绘及其他应用的注释工具。
Automating the annotation of benthic imagery (i.e., images of the seafloor and its associated organisms, habitats, and geological features) is critical for monitoring rapidly changing ocean ecosystems. Deep learning approaches have succeeded in this purpose; however, consistent annotation remains challenging due to ambiguous seafloor images, potential inter-user annotation disagreements, and out-of-distribution samples. Marine scientists implementing deep learning models often obtain predictions based on one-hot representations trained using a cross-entropy loss objective with softmax normalization, resulting with a single set of model parameters. While efficient, this approach may lead to overconfident predictions for context-challenging datasets, raising reliability concerns that present risks for downstream tasks such as benthic habitat mapping and marine spatial planning. In this study, we investigated classification uncertainty as a tool to improve the labeling of benthic habitat imagery. We developed a framework for two challenging sub-datasets of the recently publicly available BenthicNet dataset using Bayesian neural networks, Monte Carlo dropout inference sampling, and a proposed single last-layer committee machine. This approach resulted with a > 95% reduction of network parameters to obtain per-sample uncertainties while obtaining near-identical performance compared to computationally more expensive strategies such as Bayesian neural networks, Monte Carlo dropout, and deep ensembles. The method proposed in this research provides a strategy for obtaining prioritized lists of uncertain samples for human-in-the-loop interventions to identify ambiguous, mislabeled, out-of-distribution, and/or difficult images for enhancing existing annotation tools for benthic mapping and other applications.
HIV预防的数值最优控制与动态预算分配
Dmitry Gromov, Ingo Bulla, Ethan O. Romero-Severson, Oana Silvia Serea
AI总结 本文提出了一种新的HIV传播模型,并利用数值最优控制方法计算最优控制策略,最终将结果应用于实际问题,取得了重要的实践意义。
本文研究HIV传播的数值控制问题。本文的贡献有三方面:首先,提出了一种新的HIV传播模型;其次,将数值最优控制方法成功应用于该模型以计算最优控制策略;最后,将计算结果应用于实际问题,取得了重要且具有实际意义的结果。
This paper is about numerical control of HIV propagation. The contribution of the paper is threefold: first, a novel model of HIV propagation is proposed; second, the methods from numerical optimal control are successfully applied to the developed model to compute optimal control profiles; finally, the computed results are applied to the real problem yielding important and practically relevant results.
机械转导动力学模型的数值分析揭示了由细胞外基质介导的间质干细胞命运振荡的同宿分岔
Katiana Kontolati, Constantinos Siettos
AI总结 研究通过数值分析揭示了机械转导模型中细胞外基质介导的间质干细胞命运振荡的同宿分岔现象,探讨了细胞分化中的非线性行为及多稳态特性。
我们对一个近似描述间质干细胞分化为神经元、脂肪细胞、心肌细胞和成骨细胞动态的机械转导模型进行了单参数和双参数数值分岔分析。在分析中,我们将细胞外基质的刚度和与正反馈机制相关的参数作为分岔参数,这些正反馈机制上调了YAP/TAZ转录调控因子(TRs)和细胞粘附面积的产生。我们的分析揭示了细胞分化的丰富非线性行为,包括滞回和多稳态区域、有效粘附面积的稳定振荡、与脂肪生成命运相关的YAP/TAZ TRs和PPARγ受体的振荡,以及中断较高振幅振荡的同宿分岔。对产生振荡模式的Andronov-Hopf点的双参数分岔分析预测了这些振荡模式在软细胞外基质(<1kPa)中的存在,这一区域有利于神经生成和脂肪生成细胞命运。此外,在这些区域中,分析揭示了同宿分岔的存在,导致细胞-基质粘附的稳定振荡突然向弱粘附和高表达Tubulin beta-3链基因的表达转移,从而促进从脂肪生成到神经生成命运的相变。
We perform one and two-parameter numerical bifurcation analysis of a mechanotransduction model approximating the dynamics of mesenchymal stem cell differentiation into neurons, adipocytes, myocytes and osteoblasts. For our analysis, we use as bifurcation parameters the stiffness of the extracellular matrix and parameters linked with the positive feedback mechanisms that up-regulate the production of the YAP/TAZ transcriptional regulators (TRs) and the cell adhesion area. Our analysis reveals a rich nonlinear behaviour of the cell differentiation including regimes of hysteresis and multistability, stable oscillations of the effective adhesion area, the YAP/TAZ TRs and the PPAR$γ$ receptors associated with the adipogenic fate, as well as homoclinic bifurcations that interrupt relatively high-amplitude oscillations abruptly. The two-parameter bifurcation analysis of the Andronov-Hopf points that give birth to the oscillating patterns predicts their existence for soft extracellular substrates ($<1kPa$), a regime that favours the neurogenic and the adipogenic cell fate. Furthermore, in these regimes, the analysis reveals the presence of homoclinic bifurcations that result in the sudden loss of the stable oscillations of the cell-substrate adhesion towards weaker adhesion and high expression levels of the gene encoding Tubulin beta-3 chain, thus favouring the phase transition from the adipogenic to the neurogenic fate.
具有复杂几何域的流体-结构相互作用中受热波动影响的空间自适应随机方法
Pat Plunkett, Jon Hu, Chris Siefert, Paul J. Atzberger
AI总结 本文提出了一种随机混合有限元方法,用于在存在热波动的情况下进行空间自适应的流体-结构相互作用模拟。通过引入离散的波动-耗散平衡条件,开发了与离散化兼容的随机驱动场。分析表明,该条件足以确保结果与统计力学一致。通过开发基于迭代方法和多重网格的吉布斯采样器,实现了高效生成所需随机驱动场。本文的方法为周期性域上的均匀离散化提供了替代方案,利用快速傅里叶变换。通过在具有内部障碍物和无滑动壁的通道几何中进行演示,展示了粒子的运动性/扩散性如何依赖于位置。本文的方法通过允许对力学进行空间自适应解析,扩展了波动流体动力学方法的应用范围,适用于许多应用中的复杂几何域。
我们开发了随机混合有限元方法,用于在存在热波动的情况下进行空间自适应的流体-结构相互作用模拟。为了考虑热波动,我们引入了一个离散的波动-耗散平衡条件,以开发与我们的离散化兼容的随机驱动场。我们进行了分析,证明该条件足以确保结果与统计力学一致。我们展示了吉布斯-玻尔兹曼分布在半离散化的随机动力学下是不变的。为了高效生成所需的随机驱动场,我们开发了基于迭代方法和多重网格的吉布斯采样器,以实现$O(N)$的计算复杂度。我们的随机方法为依赖快速傅里叶变换的周期性域上的均匀离散化提供了替代方案。为了在实践中展示我们的随机计算方法,我们研究了在具有内部障碍物和无滑动壁的通道几何中,粒子的运动性/扩散性如何依赖于位置。我们的方法通过允许对力学进行空间自适应解析,扩展了波动流体动力学方法的应用范围,适用于许多应用中的复杂几何域。
We develop stochastic mixed finite element methods for spatially adaptive simulations of fluid-structure interactions when subject to thermal fluctuations. To account for thermal fluctuations, we introduce a discrete fluctuation-dissipation balance condition to develop compatible stochastic driving fields for our discretization. We perform analysis that shows our condition is sufficient to ensure results consistent with statistical mechanics. We show the Gibbs-Boltzmann distribution is invariant under the stochastic dynamics of the semi-discretization. To generate efficiently the required stochastic driving fields, we develop a Gibbs sampler based on iterative methods and multigrid to generate fields with $O(N)$ computational complexity. Our stochastic methods provide an alternative to uniform discretizations on periodic domains that rely on Fast Fourier Transforms. To demonstrate in practice our stochastic computational methods, we investigate within channel geometries having internal obstacles and no-slip walls how the mobility/diffusivity of particles depends on location. Our methods extend the applicability of fluctuating hydrodynamic approaches by allowing for spatially adaptive resolution of the mechanics and for domains that have complex geometries relevant in many applications.