55 research outputs found
Subwavelength grating devices in silicon photonics
Subwavelength grating (SWG) waveguides in silicon-on-insulator are emerging as an enabling technology for implementing compact, high-performance photonic integrated devices and circuits for signal processing and sensing applications. We provide an overview of our recent work on developing wavelength selective SWG filters based on Bragg gratings and ring resonators, as well as optical delay lines. These components increase the SWG toolbox and can be used to realize more complex photonic integrated circuits with enhanced or new functionality
Subwavelength grating filters in SOI
We demonstrate subwavelength grating filters in silicon-on-insulator based on Bragg gratings and racetrack resonators. The Bragg grating has a 3 dB bandwidth = 0.5 nm and reflectivity > 90%; the resonator has a 3 dB bandwidth = 1 nm and extinction ratio > 33 dB
SoftGPT: Learn Goal-oriented Soft Object Manipulation Skills by Generative Pre-trained Heterogeneous Graph Transformer
Soft object manipulation tasks in domestic scenes pose a significant
challenge for existing robotic skill learning techniques due to their complex
dynamics and variable shape characteristics. Since learning new manipulation
skills from human demonstration is an effective way for robot applications,
developing prior knowledge of the representation and dynamics of soft objects
is necessary. In this regard, we propose a pre-trained soft object manipulation
skill learning model, namely SoftGPT, that is trained using large amounts of
exploration data, consisting of a three-dimensional heterogeneous graph
representation and a GPT-based dynamics model. For each downstream task, a
goal-oriented policy agent is trained to predict the subsequent actions, and
SoftGPT generates the consequences of these actions. Integrating these two
approaches establishes a thinking process in the robot's mind that provides
rollout for facilitating policy learning. Our results demonstrate that
leveraging prior knowledge through this thinking process can efficiently learn
various soft object manipulation skills, with the potential for direct learning
from human demonstrations.Comment: 6 pages, 5 figures, accepted by IROS 202
Mixline: A Hybrid Reinforcement Learning Framework for Long-horizon Bimanual Coffee Stirring Task
Bimanual activities like coffee stirring, which require coordination of dual
arms, are common in daily life and intractable to learn by robots. Adopting
reinforcement learning to learn these tasks is a promising topic since it
enables the robot to explore how dual arms coordinate together to accomplish
the same task. However, this field has two main challenges: coordination
mechanism and long-horizon task decomposition. Therefore, we propose the
Mixline method to learn sub-tasks separately via the online algorithm and then
compose them together based on the generated data through the offline
algorithm. We constructed a learning environment based on the GPU-accelerated
Isaac Gym. In our work, the bimanual robot successfully learned to grasp, hold
and lift the spoon and cup, insert them together and stir the coffee. The
proposed method has the potential to be extended to other long-horizon bimanual
tasks.Comment: 10 pages, conferenc
View-Disentangled Transformer for Brain Lesion Detection
Deep neural networks (DNNs) have been widely adopted in brain lesion
detection and segmentation. However, locating small lesions in 2D MRI slices is
challenging, and requires to balance between the granularity of 3D context
aggregation and the computational complexity. In this paper, we propose a novel
view-disentangled transformer to enhance the extraction of MRI features for
more accurate tumour detection. First, the proposed transformer harvests
long-range correlation among different positions in a 3D brain scan. Second,
the transformer models a stack of slice features as multiple 2D views and
enhance these features view-by-view, which approximately achieves the 3D
correlation computing in an efficient way. Third, we deploy the proposed
transformer module in a transformer backbone, which can effectively detect the
2D regions surrounding brain lesions. The experimental results show that our
proposed view-disentangled transformer performs well for brain lesion detection
on a challenging brain MRI dataset.Comment: International Symposium on Biomedical Imaging (ISBI) 2022, code:
https://github.com/lhaof/ISBI-VDForme
Subwavelength grating waveguide devices for telecommunications applications
Subwavelength grating (SWG) waveguides in silicon-on-insulator are emerging as an enabling technology for implementing compact, high-performance photonic integrated devices and circuits for signal processing and sensing applications. We provide an overview of recent work on developing wavelength selective SWG waveguide filters based on Bragg gratings, ring resonators, and contra-directional couplers, as well as optical delay lines for applications in optical communications and microwave photonics. These components increase the SWG waveguide component toolbox and can be used to realize more complex photonic integrated circuits with enhanced or new functionalit
Carbapenemase-Producing Escherichia coli among Humans and Backyard Animals
Background:
The rapidly increasing dissemination of carbapenem-resistant Enterobacteriaceae (CRE) in both humans and animals poses a global threat to public health. However, the transmission of CRE between humans and animals has not yet been well studied.
Objectives:
We investigated the prevalence, risk factors, and drivers of CRE transmission between humans and their backyard animals in rural China.
Methods:
We conducted a comprehensive sampling strategy in 12 villages in Shandong, China. Using the household [residents and their backyard animals (farm and companion animals)] as a single surveillance unit, we assessed the prevalence of CRE at the household level and examined the factors associated with CRE carriage through a detailed questionnaire. Genetic relationships among human- and animal-derived CRE were assessed using whole-genome sequencing–based molecular methods.
Results:
A total of 88 New Delhi metallo-β-lactamases
–type carbapenem-resistant Escherichia coli (NDM-EC), including 17 from humans, 44 from pigs, 12 from chickens, 1 from cattle, and 2 from dogs, were isolated from 65 of the 746 households examined. The remaining 12 NDM-EC were from flies in the immediate backyard environment. The NDM-EC colonization in households was significantly associated with a) the number of species of backyard animals raised/kept in the same household, and b) the use of human and/or animal feces as fertilizer. Discriminant analysis of principal components (DAPC) revealed that a large proportion of the core genomes of the NDM-EC belonged to strains from hosts other than their own, and several human isolates shared closely related core single-nucleotide polymorphisms and blaNDM
genetic contexts with isolates from backyard animals.
Conclusions:
To our knowledge, we are the first to report evidence of direct transmission of NDM-EC between humans and animals. Given the rise of NDM-EC in community and hospital infections, combating NDM-EC transmission in backyard farm systems is needed. https://doi.org/10.1289/EHP525
Push–pull type manganese (III) corroles
The synthesis of three low symmetry A2B type Mn(III)triarylcorroles with meso-aryl substituents that provide push–pull electron-donating and -withdrawing properties is reported. An analysis of the structure-property relationships for the optical and redox properties has been carried out through a comparison with the results of theoretical calculations. The results demonstrate that A2B type Mn(III)triarylcorroles interact strongly with cell-free circulating tumor deoxyribonucleic acid (ctDNA) in solution, and that the interaction constants are enhanced when a stronger electron-donating substituent is introduced at the 10-position of the meso-triarylcorrole ligand
Prevalence and factors of COVID-19 vaccine refusal among solid cancer patients in China: an application of the health belief model
IntroductionIt is essential to protect cancer patients from contracting COVID-19 through vaccination. A majority of cancer patients are recommended by international health authorities to take up the vaccines. COVID-19 vaccine refusal among cancer patients during the pandemic period is under-researched. This study investigated factors of vaccine refusal based on the Health Belief Model (HBM).MethodsA cross-sectional study was conducted among female breast cancer patients, male/female thyroid cancer patients, and gynecological cancer patients in Shantou, China from April to August 2022 (n = 1,115). Multinomial logistic regression analysis adjusted for socio-demographics was conducted to test factors of COVID-19. Adjusted odds ratios of the two models comparing vaccine refusal vs. “vaccine non-refusal” and vaccine refusal vs. ever-vaccination were derived and presented.ResultsOf all the participants, the prevalence of vaccine refusal, “vaccine non-refusal,” and ever-vaccination was 25.9, 22.2, and 51.8%, respectively. In both multinomial logistic regression models, significant factors of vaccine refusal included socio-demographics (age, education level, employment status, monthly household income, cancer type, duration since cancer diagnosis, current treatment status) and some vaccine-related HBM (perceived benefits, perceived barriers, cue to action, and self-efficacy). Perceived severity of COVID-19 was significant only in the vaccine refusal vs. ever-vaccination model. In neither model, perceived susceptibility to contract COVID-19 was statistically significant.ConclusionAbout ¼ of the participants expressed vaccine refusal. Interventions are warranted. Future longitudinal studies are needed to verify this study’s findings. Pilot interventions should also be launched to test effectiveness of interventions modifying the significant HBM factors found in this study
Performance and characterization of the SPT-3G digital frequency-domain multiplexed readout system using an improved noise and crosstalk model
The third-generation South Pole Telescope camera (SPT-3G) improves upon its predecessor (SPTpol) by an order of magnitude increase in detectors on the focal plane. The technology used to read out and control these detectors, digital frequency-domain multiplexing (DfMUX), is conceptually the same as used for SPTpol, but extended to accommodate more detectors. A nearly 5Ă— expansion in the readout operating bandwidth has enabled the use of this large focal plane, and SPT-3G performance meets the forecasting targets relevant to its science objectives. However, the electrical dynamics of the higher-bandwidth readout differ from predictions based on models of the SPTpol system due to the higher frequencies used and parasitic impedances associated with new cryogenic electronic architecture. To address this, we present an updated derivation for electrical crosstalk in higher-bandwidth DfMUX systems and identify two previously uncharacterized contributions to readout noise, which become dominant at high bias frequency. The updated crosstalk and noise models successfully describe the measured crosstalk and readout noise performance of SPT-3G. These results also suggest specific changes to warm electronics component values, wire-harness properties, and SQUID parameters, to improve the readout system for future experiments using DfMUX, such as the LiteBIRD space telescope
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