Deep learning methods have recently been successfully explored for hyperspectral image (HSI) classification. However, training a deep-learning classifier notoriously requires hundreds or thousands of ...labeled samples. In this paper, a deep few-shot learning method is proposed to address the small sample size problem of HSI classification. There are three novel strategies in the proposed algorithm. First, spectral-spatial features are extracted to reduce the labeling uncertainty via a deep residual 3-D convolutional neural network. Second, the network is trained by episodes to learn a metric space where samples from the same class are close and those from different classes are far. Finally, the testing samples are classified by a nearest neighbor classifier in the learned metric space. The key idea is that the designed network learns a metric space from the training data set. Furthermore, such metric space could generalize to the classes of the testing data set. Note that the classes of the testing data set are not seen in the training data set. Four widely used HSI data sets were used to assess the performance of the proposed algorithm. The experimental results indicate that the proposed method can achieve better classification accuracy than the conventional semisupervised methods with only a few labeled samples.
Abstract
Single-atom catalysts (SACs) have sparked broad interest recently while the low metal loading poses a big challenge for further applications. Herein, a dual protection strategy has been ...developed to give high-content SACs by nanocasting SiO
2
into porphyrinic metal–organic frameworks (MOFs). The pyrolysis of SiO
2
@MOF composite affords single-atom Fe implanted N-doped porous carbon (Fe
SA
–N–C) with high Fe loading (3.46 wt%). The spatial isolation of Fe atoms centered in porphyrin linkers of MOF sets the first protective barrier to inhibit the Fe agglomeration during pyrolysis. The SiO
2
in MOF provides additional protection by creating thermally stable FeN
4
/SiO
2
interfaces. Thanks to the high-density Fe
SA
sites, Fe
SA
–N–C demonstrates excellent oxygen reduction performance in both alkaline and acidic medias. Meanwhile, Fe
SA
–N–C also exhibits encouraging performance in proton exchange membrane fuel cell, demonstrating great potential for practical application. More far-reaching, this work grants a general synthetic methodology toward high-content SACs (such as Fe
SA
, Co
SA
, Ni
SA
).
•Ultrasound treatment (PUS) could increase lipid and protein oxidation significantly.•Protein aggregation occurred according to SDS–PAGE analysis.•Free sulfhydryl contents and protein surface ...hydrophobicity increased after PUS.•FTIR showed the increases in β-sheets while decreases in α-helix structures after PUS.
The aim of this study was to evaluate the effects of power ultrasound intensity (PUS, 2.39, 6.23, 11.32 and 20.96Wcm−2) and treatment time (30, 60, 90 and 120min) on the oxidation and structure of beef proteins during the brining procedure with 6% NaCl concentration. The investigation was conducted with an ultrasonic generator with the frequency of 20kHz and fresh beef at 48h after slaughter. Analysis of TBARS (Thiobarbituric acid reactive substances) contents showed that PUS treatment significantly increased the extent of lipid oxidation compared to static brining (P<0.05). As indicators of protein oxidation, the carbonyl contents were significantly affected by PUS (P<0.05). SDS–PAGE analysis showed that PUS treatment increased protein aggregation through disulfide cross-linking, indicated by the decreasing content of total sulfhydryl groups which would contribute to protein oxidation. In addition, changes in protein structure after PUS treatment are suggested by the increases in free sulfhydryl residues and protein surface hydrophobicity. Fourier transformed infrared spectroscopy (FTIR) provided further information about the changes in protein secondary structures with increases in β-sheet and decreases in α-helix contents after PUS processing. These results indicate that PUS leads to changes in structures and oxidation of beef proteins caused by mechanical effects of cavitation and the resultant generation of free radicals.
Background
With the onset of the coronavirus disease 2019 (COVID‐19) pandemic, many experts expected that asthma‐associated morbidity because of severe acute respiratory syndrome coronavirus 2 ...infection would dramatically increase. However, some studies suggested that there was no apparent increasing in asthma‐related morbidity in children with asthma, it is even possible children may have improved outcomes. To understand the relationship between the COVID‐19 pandemic and asthma outcomes, we performed this article.
Methods
We searched PubMed, Embase, and Cochrane Library to find literature from December 2019 to June 2021 related to COVID‐19 and children's asthma control, among which results such as s, comments, letters, reviews, and case reports were excluded. The level of asthma control during the COVID‐19 pandemic was synthesized and discussed by outcomes of asthma exacerbation, emergency room visit, asthma admission, and childhood asthma control test (c‐ACT).
Results
A total of 22,159 subjects were included in 10 studies. Random effect model was used to account for the data. Compared with the same period before the COVID‐19 pandemic, asthma exacerbation reduced (odds ratio OR = 0.26, 95% confidence interval CI = 0.14–0.48, Z = 4.32, p < 0.0001), the odds of emergency room visit decreased as well (OR = 0.11, 95% CI = 0.04–0.26, Z = 4.98, p < 0.00001). The outcome of asthma admission showed no significant difference (OR = 0.84, 95% CI = 0.32–2.20, Z = 0.36, p = 0.72). The outcome of c‐ACT scores were not analyzed because of the different manifestations used. Overall, c‐ACT scores reduced during the pandemic.
Conclusion
Compared to the same period before the COVID‐19 pandemic, the level of asthma control has been significantly improved. We need to understand the exact factors leading to these improvements and find methods to sustain it.
It remains highly desired but a great challenge to achieve atomically dispersed metals in high loadings for efficient catalysis. Now porphyrinic metal–organic frameworks (MOFs) have been synthesized ...based on a novel mixed‐ligand strategy to afford high‐content (1.76 wt %) single‐atom (SA) iron‐implanted N‐doped porous carbon (FeSA‐N‐C) via pyrolysis. Thanks to the single‐atom Fe sites, hierarchical pores, oriented mesochannels and high conductivity, the optimized FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and state‐of‐the‐art Pt/C, in both alkaline and more challenging acidic media. More far‐reaching, this MOF‐based mixed‐ligand strategy opens a novel avenue to the precise fabrication of efficient single‐atom catalysts.
Iron islands: Based on a mixed‐ligand strategy, a porphyrinic MOF was pyrolyzed to afford high‐content single‐atom iron‐implanted N‐doped porous carbon (FeSA‐N‐C). Thanks to the FeSA sites, hierarchical pores, oriented mesochannels, and high conductivity, FeSA‐N‐C exhibits excellent oxygen reduction activity and stability, surpassing almost all non‐noble‐metal catalysts and Pt/C, in both alkaline and the more challenging acidic media.
Single‐atom catalysts (SACs) are of great interest because of their ultrahigh activity and selectivity. However, it is difficult to construct model SACs according to a general synthetic method, and ...therefore, discerning differences in activity of diverse single‐atom catalysts is not straightforward. Herein, a general strategy for synthesis of single‐atom metals implanted in N‐doped carbon (M1‐N‐C; M=Fe, Co, Ni and Cu) has been developed starting from multivariate metal–organic frameworks (MOFs). The M1‐N‐C catalysts, featuring identical chemical environments and supports, provided an ideal platform for differentiating the activity of single‐atom metal species. When employed in electrocatalytic CO2 reduction, Ni1‐N‐C exhibited a very high CO Faradaic efficiency (FE) up to 96.8 % that far surpassed Fe1‐, Co1‐ and Cu1‐N‐C. Remarkably, the best‐performer, Ni1‐N‐C, even demonstrated excellent CO FE at low CO2 pressures, thereby representing a promising opportunity for the direct use of dilute CO2 feedstock.
A series of porphyrinic multivariate metal–organic frameworks (MTV‐MOFs) were pyrolyzed to generate a range of single‐atom metals implanted in N‐doped carbon (M1‐N‐C; M=Fe, Co, Ni and Cu). The M1‐N‐C model catalysts, with an almost identical carbon support environment, demonstrated different activities toward CO2 electroreduction. The best performer, Ni1‐N‐C, achieved highly selective reduction of CO2 even at low pressures.
The objective of this study was to investigate the biochemical difference of pork under high oxygen modified atmosphere packaging and their contribution to meat tenderness and water holding capacity ...of pork during postmortem storage. Twelve longissimus dorsi muscles were randomly assigned to either high oxygen modified atmosphere packaging or vacuum packaging and stored for 1, 4, and 6 days at 4 °C. The carbonyl content, protein surface hydrophobicity, protein solubility, calpain activity, desmin degradation, tenderness, and water loss of pork were determined. Results showed that carbonyl content, protein surface hydrophobicity, and protein solubility were significantly affected (
P
< 0.05) by packaging method, while storage time did not significantly influence protein surface hydrophobicity and the solubility of sarcoplasmic protein (
P
> 0.05). Samples from high oxygen modified atmosphere packaging at 1 day showed greater intensity of intact 80 KDa calpain and lower intensity of autolyzed 76 KDa calpain product compared to samples from vacuum packaging (
P
< 0.05). Desmin degradation was significantly affected (
P
< 0.05) by packaging method and storage time, while their interaction presented no significance (
P
> 0.05). Higher intensity of intact desmin was observed in samples from high oxygen modified atmosphere packaging than vacuum packaging samples from 1 day of postmortem storage. Both packaging method and storage time showed significant effects (
P
< 0.05) on tenderness and water loss of pork muscle during postmortem storage. Changes in protein oxidation, calpain activation, and protein proteolysis of postmortem pork under high oxygen modified atmosphere packaging could help to explain decreased meat tenderness and increased centrifuge loss of pork.
•Ultrasound (PUS) could increase the WHC and tenderness of beef during curing.•LF-NMR analysis showed that PUS could induce the higher P21 values of beef.•Higher ratio of myosin oligomer was related ...to the increased WHC of beef by PUS.•PUS could increase the MFI values and the extent of myofibril proteolysis of beef.
The objective of this study was to explore the mechanisms of power ultrasound (PUS, 150 and 300W) and treatment time (30 and 120min) on the water-holding capacity (WHC) and tenderness of beef during curing. Beef muscle at 48h post mortem was subjected to PUS treatment at a frequency of 20kHz. Analysis of compression loss and shear force showed that PUS-assisted curing significantly increased the WHC and the tenderness of beef compared to static brining (p<0.05). According to the analysis of LF-NMR, PUS treatment could increase the P21 values which indicated an improvement in water-binding ability of beef muscle. SDS-PAGE and LC-ESI-MS/MS analysis suggested that PUS induced moderate oxidation of myosin causing polymerization, which may contribute to increased water retention. On the other hand, an increased tenderness of beef is suggested by the increased MFI values and proteolysis of desmin and troponin-T. Transmission electron microscopy (TEM) further supported the effects of PUS on WHC and tenderness changes due to the swelling and disruption of myofibrils. Thus, these results provide knowledge about the mechanism for improving WHC and tenderness of beef by PUS curing, which could be employed as an emerging technology for various meat curing processes.
The effects of ultrasound intensity and salt concentration of brining for accelerating brine transfer into beef were evaluated. Samples were analyzed with NaCl and water content, effective diffusion ...coefficient and microstructure. Results showed that ultrasound intensity and NaCl concentration of brine could significantly affect NaCl and moisture content at different treating time during meat brining (p<0.05). According to the calculation of diffusion coefficients (D), measured and calculated data were consistent indicating the fitness of the applied model. The D values of NaCl or water significantly increased with ultrasound intensity while the salt concentration was slightly affected by D values of NaCl or water. These facts could be confirmed by microstructural analysis with TEM which illustrated that the space of separation of myofibrils improved with ultrasound intensity. However, with the different salt concentration of brining, ultrasound intensity 20.96W/cm2 caused a nearly consistent result of myofibrils ruptured but significantly better than other ultrasound intensity (p<0.05). Therefore, ultrasound could be considered a potential method to accelerate the brining process in meat products.
In our research, the ultrasound intensity could significantly affect diffusion coefficients (D) of NaCl or water while the salt concentration with ultrasound processing was slightly affected the values of D, these results indicated that in industrial application, we might focus on the effect of ultrasound intensity. In addition, along with the emerging technology, this could reduce the amount of NaCl supplemented in brining and shorten the processing time.
•US and NaCl concentration could significantly improve NaCl and moisture content during meat brining.•US could improve the diffusion coefficients (D) of NaCl or water while the salt concentration was slightly affected the D.•US intensity could significantly affect myofibrils structure during treatment.•Salt concentration caused a nearly consistent myofibrils ruptured at the same US intensity.
Summary
This study evaluated the effects of freezing method and storage time on the quality changes of pork longissimus thoracis (LT). The results showed that, compared to air blast freezing (AF), ...better microstructure was observed in pork under immersion solution freezing (ISF) mainly due to higher freezing rate. ISF group had significantly lower thawing loss at 1, 31 and 91 days and higher shear force at 1 day than AF (P < 0.05). A significant reduction in TBARS value at 61 and 91 days was observed in ISF samples (P < 0.05). No significant differences were observed between the two treatments in the colour, cooking loss and sulfhydryl groups (P > 0.05). All quality indicators were significantly affected by storage time (P < 0.05). It is concluded that ISF could maintain better microstructure, improve water‐holding capacity and inhibit lipid oxidation during pork LT frozen storage.
Pork longissimus thoracis was obtained at 24 h after slaughter. To determine the effects of two freezing methods on pork quality changes during frozen storage, muscles were randomly assigned to two treatments including air blast freezing (‐22 ℃) and immersion solution freezing (‐22 ℃). When the center temperature of pork reached to ‐18 ℃, the pork samples were preserved at ‐18 ℃ for 1, 31, 61, and 91 days. Then the microstructure, color, pH value, water‐holding capacity, shear force, thiobarbituric acid‐reactive substances (TBARS) value, total and free sulfhydryl group content of samples were analyzed.
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