256 research outputs found
Conditional Lie-Bäcklund Symmetries and Reductions of the Nonlinear Diffusion Equations with Source
Conditional Lie-Bäcklund symmetry approach is used to study the invariant subspace of the nonlinear diffusion equations with source ut=e−qx(epxP(u)uxm)x+Q(x,u), m≠1. We obtain a complete list of canonical forms for such equations admit multidimensional invariant subspaces determined by higher order conditional Lie-Bäcklund symmetries. The resulting equations are either solved exactly or reduced to some finite-dimensional dynamic systems
FoxM1B transcriptionally regulates vascular endothelial growth factor expression and promotes the angiogenesis and growth of glioma cells.
We previously found that FoxM1B is overexpressed in human glioblastomas and that forced FoxM1B expression in anaplastic astrocytoma cells leads to the formation of highly angiogenic glioblastoma in nude mice. However, the molecular mechanisms by which FoxM1B enhances glioma angiogenesis are currently unknown. In this study, we found that vascular endothelial growth factor (VEGF) is a direct transcriptional target of FoxM1B. FoxM1B overexpression increased VEGF expression, whereas blockade of FoxM1 expression suppressed VEGF expression in glioma cells. Transfection of FoxM1 into glioma cells directly activated the VEGF promoter, and inhibition of FoxM1 expression by FoxM1 siRNA suppressed VEGF promoter activation. We identified two FoxM1-binding sites in the VEGF promoter that specifically bound to the FoxM1 protein. Mutation of these FoxM1-binding sites significantly attenuated VEGF promoter activity. Furthermore, FoxM1 overexpression increased and inhibition of FoxM1 expression suppressed the angiogenic ability of glioma cells. Finally, an immunohistochemical analysis of 59 human glioblastoma specimens also showed a significant correlation between FoxM1 overexpression and elevated VEGF expression. Our findings provide both clinical and mechanistic evidence that FoxM1 contributes to glioma progression by enhancing VEGF gene transcription and thus tumor angiogenesis
Pre-trained transformer for adversarial purification
With more and more deep neural networks being deployed as various daily
services, their reliability is essential. It's frightening that deep neural
networks are vulnerable and sensitive to adversarial attacks, the most common
one of which for the services is evasion-based. Recent works usually strengthen
the robustness by adversarial training or leveraging the knowledge of an amount
of clean data. However, in practical terms, retraining and redeploying the
model need a large computational budget, leading to heavy losses to the online
service. In addition, when adversarial examples of a certain attack are
detected, only limited adversarial examples are available for the service
provider, while much clean data may not be accessible. Given the mentioned
problems, we propose a new scenario, RaPiD (Rapid Plug-in Defender), which is
to rapidly defend against a certain attack for the frozen original service
model with limitations of few clean and adversarial examples. Motivated by the
generalization and the universal computation ability of pre-trained transformer
models, we come up with a new defender method, CeTaD, which stands for
Considering Pre-trained Transformers as Defenders. In particular, we evaluate
the effectiveness and the transferability of CeTaD in the case of one-shot
adversarial examples and explore the impact of different parts of CeTaD as well
as training data conditions. CeTaD is flexible, able to be embedded into an
arbitrary differentiable model, and suitable for various types of attacks
Decomposing Uncertainty for Large Language Models through Input Clarification Ensembling
Uncertainty decomposition refers to the task of decomposing the total
uncertainty of a model into data (aleatoric) uncertainty, resulting from the
inherent complexity or ambiguity of the data, and model (epistemic)
uncertainty, resulting from the lack of knowledge in the model. Performing
uncertainty decomposition for large language models (LLMs) is an important step
toward improving the reliability, trustworthiness, and interpretability of
LLMs, but this research task is very challenging and remains unresolved. The
existing canonical method, Bayesian Neural Network (BNN), cannot be applied to
LLMs, because BNN requires training and ensembling multiple variants of models,
which is infeasible or prohibitively expensive for LLMs. In this paper, we
introduce an uncertainty decomposition framework for LLMs, called input
clarifications ensemble, which bypasses the need to train new models. Rather
than ensembling models with different parameters, our approach generates a set
of clarifications for the input, feeds them into the fixed LLMs, and ensembles
the corresponding predictions. We show that our framework shares a symmetric
decomposition structure with BNN. Empirical evaluations demonstrate that the
proposed framework provides accurate and reliable uncertainty quantification on
various tasks. Code will be made publicly available at
https://github.com/UCSB-NLP-Chang/llm_uncertainty .Comment: 15 pages, 3 figure
Harnessing the Spatial-Temporal Attention of Diffusion Models for High-Fidelity Text-to-Image Synthesis
Diffusion-based models have achieved state-of-the-art performance on
text-to-image synthesis tasks. However, one critical limitation of these models
is the low fidelity of generated images with respect to the text description,
such as missing objects, mismatched attributes, and mislocated objects. One key
reason for such inconsistencies is the inaccurate cross-attention to text in
both the spatial dimension, which controls at what pixel region an object
should appear, and the temporal dimension, which controls how different levels
of details are added through the denoising steps. In this paper, we propose a
new text-to-image algorithm that adds explicit control over spatial-temporal
cross-attention in diffusion models. We first utilize a layout predictor to
predict the pixel regions for objects mentioned in the text. We then impose
spatial attention control by combining the attention over the entire text
description and that over the local description of the particular object in the
corresponding pixel region of that object. The temporal attention control is
further added by allowing the combination weights to change at each denoising
step, and the combination weights are optimized to ensure high fidelity between
the image and the text. Experiments show that our method generates images with
higher fidelity compared to diffusion-model-based baselines without fine-tuning
the diffusion model. Our code is publicly available at
https://github.com/UCSB-NLP-Chang/Diffusion-SpaceTime-Attn.Comment: 20 pages, 16 figure
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