60 research outputs found
Stability of the solitary wave solutions to a coupled BBM system
In this work, we present a stability criteria for the solitary wave solutions
to a BBM system that contains coupled nonlinear terms. Using the idea by Bona,
Chen and Karakashian and exploiting the accurate point spectrum information of
the associated Schrodinger operator, we improve the stability results
previously got by Pereira.Comment: 15 page
A fast topology optimization method of damping material layer for noise reduction to elastic curved plate-cavity structure
This paper presents a fast topology optimization method of damping material layer for noise reduction to elastic curved plate (shell)-cavity structure. Using less as far as possible the damping materials reach the maximum efficiency of one's vibration or noise reduction. Energy method is employed. The way to determine the location where the damping material pasted on is to find the location where damping material’s energy will lose more. The computational model is based on a finite element discretization. Assuming pasting a small amount of damping materials on the structure has little effect on vibration mode, the relationship between energy loss of the damping material on each element and the displacement of the nodes of the plate (shell) during a period of vibration was deduced. Damping material was laid out on the element location where damping layer energy will lose most, and then the second gradually, until optimization target was achieved. Commercial finite element software was used to obtain the finite element model of complex engineering structures. Nodes information, stiffness and mass matrix were read out by Matlab subroutines. A numerical result of topology optimization of damping material layer on the curved plate-cavity structure noise reduction was presented. The topology optimization method is approximate, simple and suitable for complex engineering applications
Comparative Transcriptional Profiling of Melatonin Synthesis and Catabolic Genes Indicates the Possible Role of Melatonin in Developmental and Stress Responses in Rice
As a well-known animal hormone, melatonin (N-acetyl-5-methoxytryptamine) is also involved in multiple plant biological processes, especially in various stress responses. Rice is one of the most important crops, and melatonin is taken in by many people everyday from rice. However, the transcriptional profiling of melatonin-related genes in rice is largely unknown. In this study, the expression patterns of 11 melatonin related genes in rice in different periods, tissues, in response to different treatments were synthetically analyzed using published microarray data. These results suggest that the melatonin-related genes may play important and dual roles in rice developmental stages. We highlight the commonly regulation of rice melatonin-related genes by abscisic acid (ABA), jasmonic acid (JA), various abiotic stresses and pathogen infection, indicating the possible role of these genes in multiple stress responses and underlying crosstalks of plant hormones, especially ABA and JA. Taken together, this study may provide insight into the association among melatonin biosynthesis and catabolic pathway, plant development and stress responses in rice. The profile analysis identified candidate genes for further functional characterization in circadian rhythm and specific stress responses
Quantifying lens elastic properties with optical coherence elastography as a function of intraocular pressure
Normal intraocular pressure (IOP) is crucial for proper maintaining of eye-globe geometry, ocular tissue health, and visual acuity. An elevated IOP is associated with diseases such as glaucoma and uveitis. While the effects of an elevated IOP on the delicate tissues of the optic nerve head and retina are well-studied, the changes in lenticular biomechanical properties as a function of IOP are not as clear. Moreover, changes in lenticular biomechanical properties have been implicated in conditions and diseases such as presbyopia and cataract. However, measuring the biomechanical properties of the lens as it sits inside the eye-globe is a challenge, but it is necessary to correctly understand the interplay between lenticular biomechanical properties and IOP. In this work, we utilized optical coherence elastography (OCE) to measure the biomechanical properties of the porcine lens in situ
Quantifying changes in lenticular stiffness with optical coherence elastography
Maintaining a normal intraocular pressure (IOP) is important for visual health. Elevated IOPs have been implicated in many diseases, such as glaucoma and uveitis. The effects of an elevated IOP on the delicate tissues of the optic nerve head and retina are well-studied, but there is a lack of information about the effects of high IOPs on the stiffness of the crystalline lens. Changes in lenticular biomechanical properties have been implicated in diseases such as presbyopia and cataract, therefore, measuring lenticular biomechanical properties is crucial to understanding the etiology and progression of the leading causes of vision impairment. Additionally, there has been even less research focused on the effects of storage media on lenticular stiffness. Previous studies have been focused on the “gold standard” of mechanical testing on excised lenses. However, mechanical testing is invasive and destructive, and removal of the lens from the eyeglobe does not allow for properly replicating the lens environment in the eye-globe. Thus, there is a need for noninvasive measurement techniques capable of performing in situ and in vivo elastographic measurements of the lens. Here, we artificially controlled the IOP of whole porcine eye-globes (N=3). Acoustic radiation force induced low amplitude displacements (<10 µm) at the apex of the lenses, which then propagated as an elastic wave. The elastic wave propagation was detected by a phase-sensitive optical coherence elastography (PhS-OCE) system. The results show that the stiffness of the lenses increased when IOP increased from 10 mmHg IOP to 40 mmHg. Additional OCE measurements were made on excised lenses stored in various media (PBS, DMEM, and M-199) at different pHs (4-7) and at different temperatures (4°C, 22°C, and 37°C). The results show that the stiffness of the lenses increased slightly when incubated at 4°C or 22°C, but decreased when the lenses were incubated at 37°C, while lenses incubated in M-199 showed more stability in their stiffness than lenses incubated in PBS and DMEM. Moreover, the lenses stored in M-199 at a pH of 7 showed a decrease in stiffness over 24 hours, while the more acidic M-199 media caused an increase in lenticular stiffness
Dual-Reference Source-Free Active Domain Adaptation for Nasopharyngeal Carcinoma Tumor Segmentation across Multiple Hospitals
Nasopharyngeal carcinoma (NPC) is a prevalent and clinically significant
malignancy that predominantly impacts the head and neck area. Precise
delineation of the Gross Tumor Volume (GTV) plays a pivotal role in ensuring
effective radiotherapy for NPC. Despite recent methods that have achieved
promising results on GTV segmentation, they are still limited by lacking
carefully-annotated data and hard-to-access data from multiple hospitals in
clinical practice. Although some unsupervised domain adaptation (UDA) has been
proposed to alleviate this problem, unconditionally mapping the distribution
distorts the underlying structural information, leading to inferior
performance. To address this challenge, we devise a novel Sourece-Free Active
Domain Adaptation (SFADA) framework to facilitate domain adaptation for the GTV
segmentation task. Specifically, we design a dual reference strategy to select
domain-invariant and domain-specific representative samples from a specific
target domain for annotation and model fine-tuning without relying on
source-domain data. Our approach not only ensures data privacy but also reduces
the workload for oncologists as it just requires annotating a few
representative samples from the target domain and does not need to access the
source data. We collect a large-scale clinical dataset comprising 1057 NPC
patients from five hospitals to validate our approach. Experimental results
show that our method outperforms the UDA methods and achieves comparable
results to the fully supervised upper bound, even with few annotations,
highlighting the significant medical utility of our approach. In addition,
there is no public dataset about multi-center NPC segmentation, we will release
code and dataset for future research
SegRap2023: A Benchmark of Organs-at-Risk and Gross Tumor Volume Segmentation for Radiotherapy Planning of Nasopharyngeal Carcinoma
Radiation therapy is a primary and effective NasoPharyngeal Carcinoma (NPC)
treatment strategy. The precise delineation of Gross Tumor Volumes (GTVs) and
Organs-At-Risk (OARs) is crucial in radiation treatment, directly impacting
patient prognosis. Previously, the delineation of GTVs and OARs was performed
by experienced radiation oncologists. Recently, deep learning has achieved
promising results in many medical image segmentation tasks. However, for NPC
OARs and GTVs segmentation, few public datasets are available for model
development and evaluation. To alleviate this problem, the SegRap2023 challenge
was organized in conjunction with MICCAI2023 and presented a large-scale
benchmark for OAR and GTV segmentation with 400 Computed Tomography (CT) scans
from 200 NPC patients, each with a pair of pre-aligned non-contrast and
contrast-enhanced CT scans. The challenge's goal was to segment 45 OARs and 2
GTVs from the paired CT scans. In this paper, we detail the challenge and
analyze the solutions of all participants. The average Dice similarity
coefficient scores for all submissions ranged from 76.68\% to 86.70\%, and
70.42\% to 73.44\% for OARs and GTVs, respectively. We conclude that the
segmentation of large-size OARs is well-addressed, and more efforts are needed
for GTVs and small-size or thin-structure OARs. The benchmark will remain
publicly available here: https://segrap2023.grand-challenge.orgComment: A challenge report of SegRap2023 (organized in conjunction with
MICCAI2023
The Persistent Circulation of Enterovirus 71 in People's Republic of China: Causing Emerging Nationwide Epidemics Since 2008
Emerging epidemics of hand-foot-and-mouth disease (HFMD) associated with enterovirus 71 (EV71) has become a serious concern in mainland China. It caused 126 and 353 fatalities in 2008 and 2009, respectively. The epidemiologic and pathogenic data of the outbreak collected from national laboratory network and notifiable disease surveillance system. To understand the virological evolution of this emerging outbreak, 326 VP1 gene sequences of EV71 detected in China from 1987 to 2009 were collected for genetic analyses. Evidence from both traditional and molecular epidemiology confirmed that the recent HFMD outbreak was an emerging one caused by EV71 of subgenotype C4. This emerging HFMD outbreak is associated with EV71 of subgenotype C4, circulating persistently in mainland China since 1998, but not attributed to the importation of new genotype. Originating from 1992, subgenotype C4 has been the predominant genotype since 1998 in mainland China, with an evolutionary rate of 4.6∼4.8×10−3 nucleotide substitutions/site/year. The phylogenetic analysis revealed that the majority of the virus during this epidemic was the most recent descendant of subgenotype C4 (clade C4a). It suggests that the evolution might be one of the potential reasons for this native virus to cause the emerging outbreak in China. However, strong negative selective pressure on VP1 protein of EV71 suggested that immune escape might not be the evolving strategy of EV71, predicting a light future for vaccine development. Nonetheless, long-term antigenic and genetic surveillance is still necessary for further understanding
Well-posedness for a higher-order, nonlinear, dispersive equation on a quarter plane
The focus of the current paper is the higher order nonlinear dispersive equation which models unidirectional propagation of small amplitude long waves in dispersive media. The specific interest is in the initial-boundary value problem where spatial variable lies in R+; namely, quarter plane problem. With proper requirement on initial and boundary condition, we show local and global well posedness
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