317 research outputs found
Quantum Thermodynamics: Inside-Outside Perspective
We introduce an energy-resolved variant of quantum thermodynamics for open
systems strongly coupled to their baths. The approach generalizes the
Landauer-Buttiker inside-outside duality method [Phys. Rev. Lett. 120, 107701
(2018)] to interacting systems subjected to arbitrary external driving. It is
consistent with the underlying dynamical quantum transport description and is
capable of overcoming limitations of the only other consistent approach [New J.
Phys. 12, 013013 (2010)]. We illustrate viability of the generalized
inside-outside method with numerical simulations for generic junction models.Comment: 11 pages, 3 figure
Graph Neural Networks based Log Anomaly Detection and Explanation
Event logs are widely used to record the status of high-tech systems, making
log anomaly detection important for monitoring those systems. Most existing log
anomaly detection methods take a log event count matrix or log event sequences
as input, exploiting quantitative and/or sequential relationships between log
events to detect anomalies. Unfortunately, only considering quantitative or
sequential relationships may result in low detection accuracy. To alleviate
this problem, we propose a graph-based method for unsupervised log anomaly
detection, dubbed Logs2Graphs, which first converts event logs into attributed,
directed, and weighted graphs, and then leverages graph neural networks to
perform graph-level anomaly detection. Specifically, we introduce One-Class
Digraph Inception Convolutional Networks, abbreviated as OCDiGCN, a novel graph
neural network model for detecting graph-level anomalies in a collection of
attributed, directed, and weighted graphs. By coupling the graph representation
and anomaly detection steps, OCDiGCN can learn a representation that is
especially suited for anomaly detection, resulting in a high detection
accuracy. Importantly, for each identified anomaly, we additionally provide a
small subset of nodes that play a crucial role in OCDiGCN's prediction as
explanations, which can offer valuable cues for subsequent root cause
diagnosis. Experiments on five benchmark datasets show that Logs2Graphs
performs at least on par with state-of-the-art log anomaly detection methods on
simple datasets while largely outperforming state-of-the-art log anomaly
detection methods on complicated datasets.Comment: Preprint submitted to Engineering Applications of Artificial
Intelligenc
Wardrop Equilibrium Can Be Boundedly Rational: A New Behavioral Theory of Route Choice
As one of the most fundamental concepts in transportation science, Wardrop
equilibrium (WE) has always had a relatively weak behavioral underpinning. To
strengthen this foundation, one must reckon with bounded rationality in human
decision-making processes, such as the lack of accurate information, limited
computing power, and sub-optimal choices. This retreat from behavioral
perfectionism in the literature, however, was typically accompanied by a
conceptual modification of WE. Here we show that giving up perfect rationality
need not force a departure from WE. On the contrary, WE can be reached with
global stability in a routing game played by boundedly rational travelers. We
achieve this result by developing a day-to-day (DTD) dynamical model that
mimics how travelers gradually adjust their route valuations, hence choice
probabilities, based on past experiences. Our model, called cumulative logit
(CULO), resembles the classical DTD models but makes a crucial change: whereas
the classical models assume routes are valued based on the cost averaged over
historical data, ours values the routes based on the cost accumulated. To
describe route choice behaviors, the CULO model only uses two parameters, one
accounting for the rate at which the future route cost is discounted in the
valuation relative to the past ones and the other describing the sensitivity of
route choice probabilities to valuation differences. We prove that the CULO
model always converges to WE, regardless of the initial point, as long as the
behavioral parameters satisfy certain mild conditions. Our theory thus upholds
WE's role as a benchmark in transportation systems analysis. It also resolves
the theoretical challenge posed by Harsanyi's instability problem by explaining
why equally good routes at WE are selected with different probabilities
Enhancing the Protein Tertiary Structure Prediction by Multiple Sequence Alignment Generation
The field of protein folding research has been greatly advanced by deep
learning methods, with AlphaFold2 (AF2) demonstrating exceptional performance
and atomic-level precision. As co-evolution is integral to protein structure
prediction, AF2's accuracy is significantly influenced by the depth of multiple
sequence alignment (MSA), which requires extensive exploration of a large
protein database for similar sequences. However, not all protein sequences
possess abundant homologous families, and consequently, AF2's performance can
degrade on such queries, at times failing to produce meaningful results. To
address this, we introduce a novel generative language model, MSA-Augmenter,
which leverages protein-specific attention mechanisms and large-scale MSAs to
generate useful, novel protein sequences not currently found in databases.
These sequences supplement shallow MSAs, enhancing the accuracy of structural
property predictions. Our experiments on CASP14 demonstrate that MSA-Augmenter
can generate de novo sequences that retain co-evolutionary information from
inferior MSAs, thereby improving protein structure prediction quality on top of
strong AF2
An 89.3% Current Efficiency, Sub 0.1% THD Current Driver for Electrical Impedance Tomography
Accurate electrical impedance tomography (EIT) measurements require a current driver with low total harmonic distortion (THD) and high output impedance. Conventional EIT current drivers attain good performance for these parameters but at the expense of low current efficiency. This Brief presents a differential current driver based on a current feedback structure with isolated common-mode feedback, achieving very low THD, high output impedance and high current efficiency. In addition, it uses current DACs to remove any dc offsets at the output nodes. The current driver was fabricated in a 65-nm CMOS technology with 3.3 V supply. Measured results demonstrate a THD of 0.05% and 0.1% at 80 kHz, for 1 mAp-p and 1.375 mAp-p output current, respectively. The total current consumption is 1.54 mA, resulting in a maximum current efficiency of 89.3%. The measured output impedance is 1.023 MΩ at 500 kHz and 568 kΩ at 1 MHz
Electronic health record phenotyping improves detection and screening of type 2 diabetes in the general United States population: A cross-sectional, unselected, retrospective study
Objectives: In the United States, 25% of people with type 2 diabetes are
undiagnosed. Conventional screening models use limited demographic information
to assess risk. We evaluated whether electronic health record (EHR) phenotyping
could improve diabetes screening, even when records are incomplete and data are
not recorded systematically across patients and practice locations. Methods: In
this cross-sectional, retrospective study, data from 9,948 US patients between
2009 and 2012 were used to develop a pre-screening tool to predict current type
2 diabetes, using multivariate logistic regression. We compared (1) a full EHR
model containing prescribed medications, diagnoses, and traditional predictive
information, (2) a restricted EHR model where medication information was
removed, and (3) a conventional model containing only traditional predictive
information (BMI, age, gender, hypertensive and smoking status). We
additionally used a random-forests classification model to judge whether
including additional EHR information could increase the ability to detect
patients with Type 2 diabetes on new patient samples. Results: Using a
patient's full or restricted EHR to detect diabetes was superior to using basic
covariates alone (p<0.001). The random forests model replicated on out-of-bag
data. Migraines and cardiac dysrhythmias were negatively associated with type 2
diabetes, while acute bronchitis and herpes zoster were positively associated,
among other factors. Conclusions: EHR phenotyping resulted in markedly superior
detection of type 2 diabetes in a general US population, could increase the
efficiency and accuracy of disease screening, and are capable of picking up
signals in real-world records
Efficient Conversion of Phenylpyruvic Acid to Phenyllactic Acid by Using Whole Cells of Bacillus coagulans SDM
Background: Phenyllactic acid (PLA), a novel antimicrobial compound with broad and effective antimicrobial activity against both bacteria and fungi, can be produced by many microorganisms, especially lactic acid bacteria. However, the concentration and productivity of PLA have been low in previous studies. The enzymes responsible for conversion of phenylpyruvic acid (PPA) into PLA are equivocal. Methodology/Principal Findings: A novel thermophilic strain, Bacillus coagulans SDM, was isolated for production of PLA. When the solubility and dissolution rate of PPA were enhanced at a high temperature, whole cells of B. coagulans SDM could effectively convert PPA into PLA at a high concentration (37.3 g l 21) and high productivity (2.3 g l 21 h 21) under optimal conditions. Enzyme activity staining and kinetic studies identified NAD-dependent lactate dehydrogenases as the key enzymes that reduced PPA to PLA. Conclusions/Significance: Taking advantage of the thermophilic character of B. coagulans SDM, a high yield and productivity of PLA were obtained. The enzymes involved in PLA production were identified and characterized, which makes possible the rational design and construction of microorganisms suitable for PLA production with metaboli
Local and global convolutional transformer-based motor imagery EEG classification
Transformer, a deep learning model with the self-attention mechanism, combined with the convolution neural network (CNN) has been successfully applied for decoding electroencephalogram (EEG) signals in Motor Imagery (MI) Brain-Computer Interface (BCI). However, the extremely non-linear, nonstationary characteristics of the EEG signals limits the effectiveness and efficiency of the deep learning methods. In addition, the variety of subjects and the experimental sessions impact the model adaptability. In this study, we propose a local and global convolutional transformer-based approach for MI-EEG classification. The local transformer encoder is combined to dynamically extract temporal features and make up for the shortcomings of the CNN model. The spatial features from all channels and the difference in hemispheres are obtained to improve the robustness of the model. To acquire adequate temporal-spatial feature representations, we combine the global transformer encoder and Densely Connected Network to improve the information flow and reuse. To validate the performance of the proposed model, three scenarios including within-session, cross-session and two-session are designed. In the experiments, the proposed method achieves up to 1.46%, 7.49% and 7.46% accuracy improvement respectively in the three scenarios for the public Korean dataset compared with current state-of-the-art models. For the BCI competition IV 2a dataset, the proposed model also achieves a 2.12% and 2.21% improvement for the cross-session and two-session scenarios respectively. The results confirm that the proposed approach can effectively extract much richer set of MI features from the EEG signals and improve the performance in the BCI applications
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