Learning Discriminative Representation via Metric Learning for Imbalanced Medical Image Classification

Data imbalance between common and rare diseases during model training often causes intelligent diagnosis systems to have biased predictions towards common diseases. The state-of-the-art approaches apply a two-stage learning framework to alleviate the class-imbalance issue, where the first stage focuses on training of a general feature extractor and the second stage focuses on fine-tuning the classifier head for class rebalancing. However, existing two-stage approaches do not consider the fine-grained property between different diseases, often causing the first stage less effective for medical image classification than for natural image classification tasks. In this study, we propose embedding metric learning into the first stage of the two-stage framework specially to help the feature extractor learn to extract more discriminative feature representations. Extensive experiments mainly on three medical image datasets show that the proposed approach consistently outperforms existing onestage and two-stage approaches, suggesting that metric learning can be used as an effective plug-in component in the two-stage framework for fine-grained class-imbalanced image classification tasks

THE ISOKINETIC MUSCLE ASYMMETRY OF THE THIGH AT 1 YEAR AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION WAS SIGNIFICANTLY ASSOCIATED WITH GAIT ASYMMETRY

Objective: To study the correlation between muscle strength asymmetry and gait asymmetry in 1 year after （Anterior Cruciate Ligament Reconstruction， ACLR）. Methods: Twenty-five ACLR patients were enrolled in the Department of Sports Medicine, Peking University Third Hospital. Data of isokinetic muscle strength test one year after ACLR were collected. The concentric and eccentric strength of extensor and flexor muscles at 60°/s, 180°/s and 300°/s on the uninjured side and the injured side were measured respectively, and the peak value of muscle strength was analyzed. The three dimensional motion information and ground reaction force during gait were collected, and the peaks of three dimensional joint angle and moments during gait stance phase were calculated by inverse dynamics analysis. The paired-samples T test was used to analyze the difference of gait parameters and isokinetic muscle strength peaks. Spearman correlation analysis was used to study the correlation between bilateral asymmetry index of isokinetic muscle strength and gait asymmetry index. Results: One year after ACLR, the isokinetic muscle strength peaks of the flexor and extensor muscles on the injured side were significantly lower than those on the uninjured side【60°/s extensor concentric, the injured side: (1.22 ± 0.4)Nm·kg-1, uninjured side: (1.73 ± 0.42)Nm·kg-1, bilateral difference: (-0.5 ± 0.39)Nm·kg-1, P \u3c 0.01; 60°/s flexor concentric, injured side: (0.84 ± 0.19)Nm·kg-1, uninjured side: (1.05 ± 0.23)Nm·kg-1, bilateral difference: (-0.21 ± 0.14)Nm·kg-1, P \u3c 0.01】. Compared with the uninjured side, the injured side showed insufficient knee extension at the time of maximum knee extension during stance phase 【injured side: (5.25 ± 4.17) °, uninjured side: (2.24 ± 3.11) °, bilateral difference: (3.01 ± 2.44) °, P \u3c 0.01】, and the peak extension moment decreased significantly 【injured side: (0.1 ± 0.09) Nm·kg-1·m-1, (0.15 ± 0.07) Nm·kg-1·m-1, (-0.05 ± 0.06) Nm·kg-1·m-1, P \u3c 0.01】. One year after ACLR, the asymmetry of 180°/s isokinetic extensor concentric strength was significantly correlated with the asymmetry of peak flexion moment (R = 0.449, P = 0.024). The asymmetry of 60°/s isokinetic extensor concentric strength was significantly correlated with the asymmetry of peak internal rotation moment (R = 0.421, P = 0.036). One year after ACLR, asymmetries of 180°/s, 300°/s isokinetic extensor concentric strength and 60°/s isokinetic flexor eccentric strength were significantly correlated with peak asymmetries during stance phase. Conclusion: There is a significant correlation between isokinetic muscle strength asymmetry of knee and gait asymmetry. This study suggests that ACLR patients still need regular rehabilitation training to improve muscle strength and motor function 1 year after ACLR, so as to reduce the risk of reinjury and secondary injury

Antenna array calibration methods based on simultaneous perturbation

Antenna arrays have gained significant interest in millimetre-wave communication systems as an enabling technology to achieve higher capacity and mitigate the high propagation loss. Such arrays with a large bandwidth need to be efficiently calibrated to maximise their performance. An antenna array calibration method based on a stochastic approximation algorithm and simultaneous perturbation has been developed and the procedures to implement it in both frequency and time domains have been presented. The approaches to define objective functions and establish gradient approximations to fulfill a successful convergence for acquiring calibration coefficients in both domains have been explored. In the time domain implementation, only a fraction of the measurement time was required to calibrate an antenna array of ultrawide bandwidth compared with other methods using a perturbation technique. The effectiveness of the proposed method has been validated via numerical experiments in both domains

HLA Class II Genes HLA-DRB1, HLA-DPB1, and HLA-DQB1 Are Associated With the Antibody Response to Inactivated Japanese Encephalitis Vaccine

Aim: The objective of this study was to evaluate the association of the human leukocyte antigen (HLA) class II genes HLA-DRB1, HLA-DPB1, and HLA-DQB1 with the humoral immune response elicited by inactivated Japanese encephalitis (JE) vaccine (IJEV).Methods: A total of 373 individuals aged 3–12 years in the Inner Mongolia Autonomous Region in China, who received two doses of IJEV at 0 and 7 days, were enrolled in the current study. Based on the individuals' specific JE virus (JEV)-neutralizing antibodies (NAbs), they were divided into a seropositive and a seronegative group. HLA-DRB1, HLA-DPB1, and HLA-DQB1 were genotyped using a sequencing-based typing method. Next, the association of the HLA class II genes and their haplotypes with antibody response was evaluated.Results: Based on NAbs, a total of 161 individuals were classified as seropositive and 212 as seronegative. DQB1*02:01 was significantly associated with JEV seropositivity (P < 0.001, OR = 0.364, 95% CI: 0.221–0.600), while DQB1*02:02 was significantly associated with JEV seronegativity (P = 5.03 × 10−6, OR = 7.341, 95% CI: 2.876–18.736). The haplotypes DRB1*07:01-DPB1*04:01-DQB1*02:01, DRB1*15:01-DPB1*02:01-DQB1*06:02, DRB1*07:01-DQB1*02:01, and DPB1*02:01-DQB1*06:02 were very frequent in the seropositive group, while DRB1*07:01-DPB1*17:01-DQB1*02:02, DRB1*07:01-DQB1*02:02, and DPB1*17:01-DQB1*02:02 were very frequent in the seronegative group. The presence of DRB1*01:01, DRB1*04:05, DRB1*09:01, DRB1*12:02, DRB1*13:02, and DRB1*14:01 was associated with a higher geometric mean titer (GMT) of NAbs than that of DRB1*11:01 at the DRB1 locus (P < 0.05). At the DPB1 locus, the presence of DPB1*05:01 was associated with higher GMTs than that of DPB1*02:01 and DPB1*13:01 (P < 0.05), and the presence of DPB1*04:01 and DPB1*09:01 was associated with higher GMTs than that of DPB1*13:01 (P < 0.05).Conclusions: The present study suggests that HLA class II genes may influence the antibody response to IJEV

Photodynamic therapy with light-emitting diode arrays producing different light fields induces apoptosis and necrosis in gastrointestinal cancer

IntroductionLight-emitting diodes (LEDs) have become a new light source for photodynamic therapy (PDT) because of their excellent optical properties, small size, and low cost. LED arrays have so far been designed to meet the need for accurate illumination of irregular lesions. However, LED arrays determine not only the shape of the illuminated spot but also the light field, which has a significant impact on the efficacy of PDT.MethodsWe designed three types of LED arrays producing different light fields, namely an intensive LED array for a uniform light field, a sparse LED array for a non-uniform light field, and a point LED array for a Gaussian-like light field, and investigated the effect and mechanism of these light fields on PDT for gastrointestinal cancer both in vitro and in vivo.ResultsWe found that intensive LED-PDT induced earlier and more serious cell death, including apoptosis and necrosis, than sparse LED-PDT and point LED-PDT. Among the three LED arrays, the intensive LED array induced cells to produce more differential proteins (DEPs), mainly related to mitochondria, ribosomes, and nucleic acids. DEPs in cells subjected to sparse LED- and point LED-PDT were mainly involved in extracellular activities. For MGC-803 tumor-bearing mice, intensive LED-PDT and point LED-PDT had better tumor ablation effect than sparse LED-PDT. Notably, recurrence was observed on day 7 after sparse LED-PDT. VCAM-1 and ICAM-1 were highly expressed in sparse LEDs-PDT treated tumor tissues and were associated tumor angiogenesis, which in turn lead to poor tumor suppression.ConclusionsTherefore, the type of LED array significantly affected the performance of PDT for gastrointestinal cancer. Uniform light field with low power densities work better than non-uniform and Gaussian-like light fields

A New Screening Evaluation Method for Carbon Dioxide Miscible Flooding Candidate Reservoirs

Prior to the implementation of CO2 injection EOR projects, the screening evaluation of candidate reservoirs will promote the economic benefits of CO2 injection. Currently, a uniform screening method for CO2 miscible flooding does not exist. Based on more than 112 successfully implemented CO2 miscible flooding reservoirs, which was referred in 2010 Worldwide EOR Survey, and CO2 miscible flooding mechanisms, this paper picks out 12 reservoir and fluid parameters affecting CO2 miscible flooding results as comprehensive evaluation parameters for screening candidate reservoirs. According to investigations on a large number of domestic and international CO2 miscible flooding projects, the quantitative methods are determined by theoretical analyses, field experience, and probability statistics. By means of calculating the combinational weights by improved analytical hierarchy process (AHP) and entropy method and combining the advantages of technique for order preference by similarity to ideal solution (TOPSIS) with gray relational analysis to construct a new similarity nearness degree, the weighted GC-TOPSIS model is established for screening candidate reservoirs. This screening method was employed for the assessment of five classical candidate reservoirs proposed for CO2 miscible flooding. The results show that this new method can correctly evaluate and compare the potential of CO2 miscible flooding.</span

Nitrate and Nitrite Promote Formation of Tobacco-Specific Nitrosamines via Nitrogen Oxides Intermediates during Postcured Storage under Warm Temperature

Tobacco-specific nitrosamines (TSNAs) are carcinogenic and are present in cured tobacco leaves. This study was designed to elucidate the mechanisms of TSNAs formation under warm temperature storage conditions. Results showed that nitrogen oxides (NOx) were produced from nitrate and nitrite in a short period of time under 45 ∘ C and then reacted with alkaloids to form TSNAs. Nitrite was more effective than nitrate in promoting TSNAs formation during 45 ∘ C storage which may be due to the fact that nitrite can produce a large amount of NOx in comparison with nitrate. Presence of activated carbon effectively inhibited the TSNAs formation because of the adsorption of NOx on the activated carbon. The results indicated that TSNAs are derived from a gas/solid phase nitrosation reaction between NOx and alkaloids. Nitrate and nitrite are major contributors to the formation of TSNAs during warm temperature storage of tobacco