55 research outputs found
Sen2Pro: A Probabilistic Perspective to Sentence Embedding from Pre-trained Language Model
Sentence embedding is one of the most fundamental tasks in Natural Language
Processing and plays an important role in various tasks. The recent
breakthrough in sentence embedding is achieved by pre-trained language models
(PLMs). Despite its success, an embedded vector (Sen2Vec) representing a point
estimate does not naturally express uncertainty in a taskagnostic way. This
paper thereby proposes an efficient framework on probabilistic sentence
embedding (Sen2Pro) from PLMs, and it represents a sentence as a probability
density distribution in an embedding space to reflect both model uncertainty
and data uncertainty (i.e., many-to-one nature) in the sentence representation.
The proposed framework performs in a plug-and-play way without retraining PLMs
anymore, and it is easy to implement and generally applied on top of any PLM.
The superiority of Sen2Pro over Sen2Vec has been theoretically verified and
practically illustrated on different NLP tasks.Comment: Accepted to ACL2023 workshop Rep4NL
Flatness-Aware Prompt Selection Improves Accuracy and Sample Efficiency
With growing capabilities of large language models, prompting them has become
the dominant way to access them. This has motivated the development of
strategies for automatically selecting effective language prompts. In this
paper, we introduce prompt flatness, a new metric to quantify the expected
utility of a language prompt. This metric is inspired by flatness
regularization in statistical learning that quantifies the robustness of the
model towards its parameter perturbations. We provide theoretical foundations
for this metric and its relationship with other prompt selection metrics,
providing a comprehensive understanding of existing methods. Empirically, we
show that combining prompt flatness with existing metrics improves both
performance and sample efficiency. Our metric outperforms the previous prompt
selection metrics with an average increase of 5% in accuracy and 10% in Pearson
correlation across 6 classification benchmarks
Appliance of plastic hinge method considering distortional buckling in pushover analysis of cold-formed rack structure
The objective of this paper is to develop a yielding surface of thin-walled cold-formed steel members subjected to distortional buckling, and then integrate the surface into pushover analysis of rack structures. Distortional buckling is one of the dominant buckling behaviors of rack members due to their intrinsic section profile. In this study, the Axial-Moment-Moment (PMM) interaction surface for a perforated omega column is established using the finite element method and compared with the theoretical one by EN 15512. It is found that the theoretical PMM domain might be conservative. Then, pushover analyses using these two PMM surfaces along with PMM from ASCE 7 are performed on a cold-formed steel rack. The pushover curve and failure mechanism of the models are analyzed with those from a detailed shell Finite Element model and a full-scale experiment. Finally, this approach of employing distortional PMM is comprehensively assessed from computational cost and reliability for its efficiency in engineering practice.We are grateful to Natural Science Foundation of Jiangsu Province for their financial support (No: BK20191268) to this paper
The Trickle-down Impact of Reward (In-)consistency on RLHF
Standard practice within Reinforcement Learning from Human Feedback (RLHF)
involves optimizing against a Reward Model (RM), which itself is trained to
reflect human preferences for desirable generations. A notable subject that is
understudied is the (in-)consistency of RMs -- whether they can recognize the
semantic changes to different prompts and appropriately adapt their reward
assignments -- and their impact on the downstream RLHF model.
In this paper, we visit a series of research questions relevant to RM
inconsistency: (1) How can we measure the consistency of reward models? (2) How
consistent are the existing RMs and how can we improve them? (3) In what ways
does reward inconsistency influence the chatbots resulting from the RLHF model
training?
We propose Contrast Instructions -- a benchmarking strategy for the
consistency of RM. Each example in Contrast Instructions features a pair of
lexically similar instructions with different ground truth responses. A
consistent RM is expected to rank the corresponding instruction and response
higher than other combinations. We observe that current RMs trained with the
standard ranking objective fail miserably on Contrast Instructions compared to
average humans. To show that RM consistency can be improved efficiently without
using extra training budget, we propose two techniques ConvexDA and
RewardFusion, which enhance reward consistency through extrapolation during the
RM training and inference stage, respectively. We show that RLHF models trained
with a more consistent RM yield more useful responses, suggesting that reward
inconsistency exhibits a trickle-down effect on the downstream RLHF process
SemStamp: A Semantic Watermark with Paraphrastic Robustness for Text Generation
Existing watermarking algorithms are vulnerable to paraphrase attacks because
of their token-level design. To address this issue, we propose SemStamp, a
robust sentence-level semantic watermarking algorithm based on
locality-sensitive hashing (LSH), which partitions the semantic space of
sentences. The algorithm encodes and LSH-hashes a candidate sentence generated
by an LLM, and conducts sentence-level rejection sampling until the sampled
sentence falls in watermarked partitions in the semantic embedding space. A
margin-based constraint is used to enhance its robustness. To show the
advantages of our algorithm, we propose a "bigram" paraphrase attack using the
paraphrase that has the fewest bigram overlaps with the original sentence. This
attack is shown to be effective against the existing token-level watermarking
method. Experimental results show that our novel semantic watermark algorithm
is not only more robust than the previous state-of-the-art method on both
common and bigram paraphrase attacks, but also is better at preserving the
quality of generation
Mechanisms of action and synergetic formulas of plant-based natural compounds from traditional Chinese medicine for managing osteoporosis: a literature review
Osteoporosis (OP) is a systemic skeletal disease prevalent in older adults, characterized by substantial bone loss and deterioration of microstructure, resulting in heightened bone fragility and risk of fracture. Traditional Chinese Medicine (TCM) herbs have been widely employed in OP treatment owing to their advantages, such as good tolerance, low toxicity, high efficiency, and minimal adverse reactions. Increasing evidence also reveals that many plant-based compounds (or secondary metabolites) from these TCM formulas, such as resveratrol, naringin, and ginsenoside, have demonstrated beneficial effects in reducing the risk of OP. Nonetheless, the comprehensive roles of these natural products in OP have not been thoroughly clarified, impeding the development of synergistic formulas for optimal OP treatment. In this review, we sum up the pathological mechanisms of OP based on evidence from basic and clinical research; emphasis is placed on the in vitro and preclinical in vivo evidence-based anti-OP mechanisms of TCM formulas and their chemically active plant constituents, especially their effects on imbalanced bone homeostasis regulated by osteoblasts (responsible for bone formation), osteoclasts (responsible for bone resorption), bone marrow mesenchymal stem cells as well as bone microstructure, angiogenesis, and immune system. Furthermore, we prospectively discuss the combinatory ingredients from natural products from these TCM formulas. Our goal is to improve comprehension of the pharmacological mechanisms of TCM formulas and their chemically active constituents, which could inform the development of new strategies for managing OP
Genome-wide selection footprints and deleterious variations in young Asian allotetraploid rapeseed
Brassica napus (AACC, 2n=38) is an important oilseed crop grown worldwide. However, little is known about the population evolution of this species, the genomic difference between its major genetic groups, such as European and Asian rapeseed, and the impacts of historical large-scale introgression events on this young tetraploid. In this study, we reported the de novo assembly of the genome sequences of an Asian rapeseed (B. napus), Ningyou 7 and its four progenitors and compared these genomes with other available genomic data from diverse European and Asian cultivars. Our results showed that Asian rapeseed originally derived from European rapeseed but subsequently significantly diverged, with rapid genome differentiation after hybridization and intensive local selective breeding. The first historical introgression of B. rapa dramatically broadened the allelic pool but decreased the deleterious variations of Asian rapeseed. The second historical introgression of the double-low traits of European rapeseed (canola) has reshaped Asian rapeseed into two groups (double-low and double-high), accompanied by an increase in genetic load in the double-low group. This study demonstrates distinctive genomic footprints and deleterious SNP (Single Nucleotide Polymorphism) variants for local adaptation by recent intra- and interspecies introgression events and provides novel insights for understanding the rapid genome evolution of a young allopolyploid cro
Draft genome sequence of the Tibetan antelope
The Tibetan antelope (Pantholops hodgsonii) is endemic to the extremely inhospitable high-altitude environment of the Qinghai-Tibetan Plateau, a region that has a low partial pressure of oxygen and high ultraviolet radiation. Here we generate a draft genome of this artiodactyl and use it to detect the potential genetic bases of highland adaptation. Compared with other plain-dwelling mammals, the genome of the Tibetan antelope shows signals of adaptive evolution and gene-family expansion in genes associated with energy metabolism and oxygen transmission. Both the highland American pika, and the Tibetan antelope have signals of positive selection for genes involved in DNA repair and the production of ATPase. Genes associated with hypoxia seem to have experienced convergent evolution. Thus, our study suggests that common genetic mechanisms might have been utilized to enable high-altitude adaptation
Finishing the euchromatic sequence of the human genome
The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead
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