Meta-learning shows great potential in plant disease recognition under few available samples.

Plant diseases worsen the threat of food shortage with the growing global population, and disease recognition is the basis for the effective prevention and control of plant diseases. Deep learning has made significant breakthroughs in the field of plant disease recognition. Compared with traditional deep learning, meta-learning can still maintain more than 90% accuracy in disease recognition with small samples. However, there is no comprehensive review on the application of meta-learning in plant disease recognition. Here, we mainly summarize the functions, advantages, and limitations of meta-learning research methods and their applications for plant disease recognition with a few data scenarios. Finally, we outline several research avenues for utilizing current and future meta-learning in plant science. This review may help plant science researchers obtain faster, more accurate, and more credible solutions through deep learning with fewer labeled samples.

Phase-modulated continuous-wave coherent ranging method for optical phased array lidar.

Light detection and ranging (lidar) is widely accepted as an indispensable sensor for autonomous vehicles. There are two fundamental challenges in a lidar system: optical beam steering technique and ranging method. Optical phased array (OPA) is considered as one of the most promising beam steering schemes due to its solid state, compact size, and high reliability. As for ranging method, time-of-flight and frequency-modulate continuous-wave (FMCW) are commonly utilized in numerous research. However, they are impractical to commercial OPA lidar due to either requiring excessive optical power or the poor stability, high complexity, and high insertion loss of the FMCW source. As a result, the development of OPA lidars is significantly hindered by the lack of a feasible ranging method. In this paper, we present a phase-modulated continuous-wave (PhMCW) ranging method with excellent ranging accuracy and precision. Ranging error as low as 0.1 cm and precision on the order of 3.5 cm are achieved. In addition, theoretical and experimental study on simultaneous velocity measurement is carried out and velocity error as low as 0.15 cm/s is obtained. Finally, we develop a proof-of-concept OPA-PhMCW lidar and obtain a point cloud with excellent fidelity. Our work paves a novel approach to solid-state, cost-effective and high-performance OPA lidars.

Contact Angle on Rough Curved Surfaces and Its Implications in Porous Media.

The equilibrium contact angle depends on both the chemistry of the two fluids and solid base and the microstructure on the solid surface. Actual surface of the pore wall in porous media is typically rough and curved, which has not been well-considered in related applications. This work uses a free interfacial energy minimization approach to theoretically derive the equilibrium contact angle on two specific surface structures on flat surfaces and extends the derivation considering the surface curvatures in porous media. Results reveal that the equilibrium contact angle is not dependent on the curvature of spherical surfaces, and we further prove that this conclusion applies to any point along the apparent common line at solid surfaces with any arbitrary curvature. The fundamental physics is the local mechanical balance of a composite contact among three interfacial tensions. Furthermore, the contacting mode can shift from non-wetting to wetting when the pressure difference between two fluids exceeds the entry pressure of the microstructures, which should be considered in relative dynamic scenarios such as rain droplet impact and fluid displacement in porous media. Note that these conclusions are from pure theoretical analysis based on idealistic assumptions, and real circumstances may deviate from these assumptions.

Femtosecond laser nanostructuring on a 4H-SiC surface by tailoring the induced self-assembled nanogratings.

Ultrafast laser micromachining of crystalline silicon carbide (SiC) has great perspectives in aerospace industry and integrated circuit technique. In this report, we present a study of femtosecond laser nanostructuring on the surface of an n-type 4H-SiC single crystal. Except for uniform nanogratings, new types of large-area periodic structures including nanoparticle array and nanoparticle-nanograting hybrid structures were induced on the surface of 4H-SiC by scanning irradiation. The effects of pulse energy, scan speed, and the polarization direction on the morphology and periodicity of nanogratings were systematically explored. The proper parameter window for nanograting formation in pulse energy-scan speed landscape is depicted. Both the uniformity and the periodicity of the induced nanogratings are polarization dependent. A planar light attenuator for linear polarized light was demonstrated by aligning the nanogratings. The transition between different large-area periodic structures is achieved by simultaneous control of pulse energy and scan interval using a cross scan strategy. These results are expected to open up an avenue to create and manipulate periodic nanostructures on SiC crystals for photonic applications.

High-Order Harmonic Film Bulk Acoustic Resonator Based on a Polymer Reflector.

A film bulk acoustic resonator (FBAR), based on a polymer air cavity, is presented. The polymer reflective layer on the polymer air cavity can serve both as the reflective layer and the function layer for inducing the high-order mode resonance. With the aluminum nitride as the piezoelectric layer, the resonance frequency of the FBAR can reach 6.360 GHz, based on the finite element method. The product of the corresponding frequency and the quality factor, f × Q is more than 2 × 1013. This design model provides a good solution for the high-frequency filters and high-sensitivity sensor designs.

High-Frequency Surface Acoustic Wave Resonator with Diamond/AlN/IDT/AlN/Diamond Multilayer Structure.

A high-frequency surface acoustic wave (SAW) resonator, based on sandwiched interdigital transducer (IDT), is presented. The resonator has the structure of diamond/AlN/IDT/AlN/diamond, with Si as the substrate. The results show that its phase velocity and electromechanical coupling coefficient are both significantly improved, compared with that of the traditional interdigital transduce-free surface structure. The M2 mode of the sandwiched structure can excite an operation frequency up to 6.15 GHz, with an electromechanical coupling coefficient of 5.53%, phase velocity of 12,470 m/s, and temperature coefficient of frequency of -6.3 ppm/°C. This structure provides a new ideal for the design of high-performance and high-frequency SAW devices.

Polarization-dependent microstructural evolution induced by a femtosecond laser in an aluminosilicate glass.

Manipulation of femtosecond laser induced microstructures in glass by tuning the laser polarization has great potential in optics. Here we report two different polarization-dependent microstructures and their evolution with pulse repetition rate in an aluminosilicate glass induced by femtosecond laser irradiation. A V-shaped crack oriented parallel to the laser polarization plane is induced at the bottom of modified regions by pulses operated at 200 kHz, 1030 nm, and 300 fs. Further increasing the pulse repetition rate to 500 kHz leads to the formation of a dumbbell-shaped structure, which is elongated perpendicularly to the laser polarization, at the top of the modified region. The size of the coloration area and the dumbbell-shaped structure can be controlled by tuning the pulse duration. Further investigation indicates that higher numerical apertures are in favor of the presence of the polarization effects in femtosecond laser irradiation. The possible mechanism responsible for the formation of the two microstructures is discussed. These results could be helpful for understanding of ultrafast laser interaction with glass.

Human MxB Inhibits the Replication of Hepatitis C Virus.

Type I interferon (IFN) inhibits viruses by inducing the expression of antiviral proteins. The IFN-induced myxovirus resistance B (MxB) protein has been reported to inhibit a limited number of viruses, including HIV-1 and herpesviruses, but its antiviral coverage remains to be explored further. Here we show that MxB interferes with RNA replication of hepatitis C virus (HCV) and significantly inhibits viral replication in a cyclophilin A (CypA)-dependent manner. Our data further show that MxB interacts with the HCV protein NS5A, thereby impairing NS5A interaction with CypA and NS5A localization to the endoplasmic reticulum, two events essential for HCV RNA replication. Interestingly, we found that MxB significantly inhibits two additional CypA-dependent viruses of the Flaviviridae family, namely, Japanese encephalitis virus and dengue virus, suggesting a potential link between virus dependence on CypA and virus susceptibility to MxB inhibition. Collectively, these data have identified MxB as a key factor behind IFN-mediated suppression of HCV infection, and they suggest that other CypA-dependent viruses may also be subjected to MxB restriction.IMPORTANCE Viruses of the Flaviviridae family cause major illness and death around the world and thus pose a great threat to human health. Here we show that IFN-inducible MxB restricts several members of the Flaviviridae, including HCV, Japanese encephalitis virus, and dengue virus. This finding not only suggests an active role of MxB in combating these major pathogenic human viruses but also significantly expands the antiviral spectrum of MxB. Our study further strengthens the link between virus dependence on CypA and susceptibility to MxB restriction and also suggests that MxB may employ a common mechanism to inhibit different viruses. Elucidating the antiviral functions of MxB advances our understanding of IFN-mediated host antiviral defense and may open new avenues to the development of novel antiviral therapeutics.

Refractive index sensor based on multiple Fano resonances in a plasmonic MIM structure.

A chip-scale refractive index sensor based on multiple Fano resonances is proposed by using a metal-insulator-metal (MIM) structure, which is constructed by two side-coupled semi-ring cavities and a vertical cavity. The finite-difference time-domain method and multimode interference coupled-mode theory are employed to simulate and analyze the transmission spectra of this structure, respectively. First, dual Fano resonances are generated in the MIM structure with a baffle and a semi-ring cavity. By arranging two additional cavities, the mode interferences successfully induce up to six ultra-sharp and asymmetrical Fano peaks. The calculated sensing performances are available with ultra-high sensitivity of 1405 nm/RIU and figure of merit of 3.62×105. This chip-scale refractive index sensor may have great applications in highly integrated photonic circuits.

Cardiotoxicity of Consolida rugulosa, a poisonous weed in Western China.

Poisonous weeds are a global problem since they not only hinder local economic development, but also cause ecological harm. Consolida rugulosa (family Ranunculaceae) is a weed that is widespread in Northwestern China and causes severe poisoning when ingested by livestock. In the present study, we purified the toxins in this plant and investigated their mechanism of action. Five natural diterpene alkaloids (compounds 1-5)-including two new compounds (1 and 2)-were isolated, and five semi-synthetic derivatives (6-10) were synthesised based on 4 or 5 for structure-activity analysis. The toxicity of the compounds was evaluated in vitro with lactate dehydrogenase (LDH) assay. All of the compounds-especially 1-stimulated LDH release in primary cultured rat myocardial cells, an effect that was blocked by the Na+ channel blocker lidocaine. Electrocardiography revealed that rats treated with 1 had severe arrhythmia, while heart Doppler echocardiography and analysis of serum biomarkers levels revealed that administration of 1 for 15 days induced changes in cardiac structure and myocardial enzyme levels. These effects were antagonised by lidocaine treatment. Thus, diterpene alkaloids are the main compounds responsible for the cardiotoxicity of C. rugulosa, which can be mitigated by co-administration of lidocaine.

Fabrication of hexagonal compound eye microlens array using DMD-based lithography with dose modulation.

In this study, a method is proposed for the rapid fabrication of a hexagonal compound eye microlens array (HCE-MLA) using maskless lithography technique based on digital micromirror device (DMD), in which a hexahedron array is lithographed, and subsequently, a microlens structure is lithographed layer by layer upon the hexahedron. Owing to the high filling rate of the hexagon and the aspheric surface of the paraboloid profile of the microlens, after the distribution of the required exposure dose of HCE-MLA was calculated based on dose modulation, a series of circular pattern with different radius could be obtained by equal-arc-mean slicing strategy that can adapt to the variable curvature of the target contour and improve its reconstruction precision. Then, after a hexagonal photoresist island was fabricated on the substrate, and the dose accumulated over multiple exposures, the required exposure dose profiles were reconstructed on the hexagonal photoresist island. Finally, a high-quality HCE-MLA with a smooth surface was fabricated via thermal reflow. The fabrication of the designed HCE-MLA using this method was demonstrated in experiments. The results indicate that the actual profile of HCE-MLA shows good agreement with the design profile and that simultaneously increasing the number of the slicing layers can improve the quality of the profile. The research indicated that this method is feasible and convenient for the fabrication of high-quality HCE-MLA.

Strontium Ranelate Combined with Insulin Is as Beneficial as Insulin Alone in Treatment of Fracture Healing in Ovariectomized Diabetic Rats.

BACKGROUND Type 2 diabetes mellitus (T2DM) and estrogen deficiency both predispose fracture patients to increased risk of delayed union or nonunion. The present study investigated the effects of strontium ranelate (SR) on fracture healing in ovariectomized (OVX) diabetic rats. MATERIAL AND METHODS A mid-shaft fracture was established in female normal control (CF), diabetic (DF), and OVX diabetic (DOF) rats. Treated DOF rats received either insulin alone (DOFI) or combined with SR (DOFIS). All rats were euthanized at 2 or 3 weeks after fracture. Fracture healing was evaluated using radiological, histological, immunohistochemical, and micro-computed tomography analyses. RESULTS At 3 weeks after fracture, radiological and histological evaluations demonstrated delayed fracture healing in the DF group compared with the CF group, which was exacerbated by OVX, as indicated by the significantly lower X-ray score, BMD, BV/TV, and Md.Ar/Ps.Cl.Ar, and the markedly decreased OCN and Col I expression in the DOF group. All these changes were prevented by insulin alone or combined with SR treatment. In comparison with the DOFI group, DOFIS rats displayed markedly higher OCN expression at 2 weeks after fracture and Col I expression at 2 and 3 weeks after fracture. CONCLUSIONS These results demonstrated delayed fracture healing with preexisting estrogen deficiency and T2DM. While insulin alone and combined with SR were both effective in promoting bone fracture healing in this model, their combined treatment showed significant improvement in promoting osteogenic marker expression, but not of the radiological appearance, compared with insulin alone.

A Plasmonic Chip-Scale Refractive Index Sensor Design Based on Multiple Fano Resonances.

In this paper, multiple Fano resonances preferred in the refractive index sensing area are achieved based on sub-wavelength metal-insulator-metal (MIM) waveguides. Two slot cavities, which are placed between or above the MIM waveguides, can support the bright modes or the dark modes, respectively. Owing to the mode interferences, dual Fano resonances with obvious asymmetrical spectral responses are achieved. High sensitivity and high figure of merit are investigated by using the finite-difference time-domain (FDTD) method. In view of the development of chip-scale integrated photonics, two extra slot cavities are successively added to the structure, and consequently, three and four ultra-sharp Fano peaks with considerable performances are obtained, respectively. It is believed that this proposed structure can find important applications in the on-chip optical sensing and optical communication areas.

Single- and dual-plasmonic induced absorption in a subwavelength end-coupled composite-square cavity.

A plasmonic end-coupled composite-square cavity (CSC) structure is proposed by adding two horizontal and normal slot cavities into a perfect square cavity (PSC) structure that is regarded as a Fabry-Perot resonator. Owing to the interference effect between the bright and dark modes, which is supported by the PSC and the slot cavities, respectively, a single plasmonic induced absorption (PIA) response with large abnormal dispersion is achieved at the former transmission peak in the CSC structure. The induced absorption window can be tuned to the wavelength of the first or second mode by using the horizontal and normal slot cavities. By changing the refractive index of the insulator inside the horizontal slot cavity, dual PIA responses are also obtained in the CSC structure. The performances of the proposed CSC structure are analyzed and investigated by using the finite-difference time-domain method.

MRI-localized biopsies reveal subtype-specific differences in molecular and cellular composition at the margins of glioblastoma.

Glioblastomas (GBMs) diffusely infiltrate the brain, making complete removal by surgical resection impossible. The mixture of neoplastic and nonneoplastic cells that remain after surgery form the biological context for adjuvant therapeutic intervention and recurrence. We performed RNA-sequencing (RNA-seq) and histological analysis on radiographically guided biopsies taken from different regions of GBM and showed that the tissue contained within the contrast-enhancing (CE) core of tumors have different cellular and molecular compositions compared with tissue from the nonenhancing (NE) margins of tumors. Comparisons with the The Cancer Genome Atlas dataset showed that the samples from CE regions resembled the proneural, classical, or mesenchymal subtypes of GBM, whereas the samples from the NE regions predominantly resembled the neural subtype. Computational deconvolution of the RNA-seq data revealed that contributions from nonneoplastic brain cells significantly influence the expression pattern in the NE samples. Gene ontology analysis showed that the cell type-specific expression patterns were functionally distinct and highly enriched in genes associated with the corresponding cell phenotypes. Comparing the RNA-seq data from the GBM samples to that of nonneoplastic brain revealed that the differentially expressed genes are distributed across multiple cell types. Notably, the patterns of cell type-specific alterations varied between the different GBM subtypes: the NE regions of proneural tumors were enriched in oligodendrocyte progenitor genes, whereas the NE regions of mesenchymal GBM were enriched in astrocytic and microglial genes. These subtype-specific patterns provide new insights into molecular and cellular composition of the infiltrative margins of GBM.

Ribosome profiling reveals a cell-type-specific translational landscape in brain tumors.

Glioma growth is driven by signaling that ultimately regulates protein synthesis. Gliomas are also complex at the cellular level and involve multiple cell types, including transformed and reactive cells in the brain tumor microenvironment. The distinct functions of the various cell types likely lead to different requirements and regulatory paradigms for protein synthesis. Proneural gliomas can arise from transformation of glial progenitors that are driven to proliferate via mitogenic signaling that affects translation. To investigate translational regulation in this system, we developed a RiboTag glioma mouse model that enables cell-type-specific, genome-wide ribosome profiling of tumor tissue. Infecting glial progenitors with Cre-recombinant retrovirus simultaneously activates expression of tagged ribosomes and delivers a tumor-initiating mutation. Remarkably, we find that although genes specific to transformed cells are highly translated, their translation efficiencies are low compared with normal brain. Ribosome positioning reveals sequence-dependent regulation of ribosomal activity in 5'-leaders upstream of annotated start codons, leading to differential translation in glioma compared with normal brain. Additionally, although transformed cells express a proneural signature, untransformed tumor-associated cells, including reactive astrocytes and microglia, express a mesenchymal signature. Finally, we observe the same phenomena in human disease by combining ribosome profiling of human proneural tumor and non-neoplastic brain tissue with computational deconvolution to assess cell-type-specific translational regulation.

E2F1 coregulates cell cycle genes and chromatin components during the transition of oligodendrocyte progenitors from proliferation to differentiation.

Cell cycle exit is an obligatory step for the differentiation of oligodendrocyte progenitor cells (OPCs) into myelinating cells. A key regulator of the transition from proliferation to quiescence is the E2F/Rb pathway, whose activity is highly regulated in physiological conditions and deregulated in tumors. In this paper we report a lineage-specific decline of nuclear E2F1 during differentiation of rodent OPC into oligodendrocytes (OLs) in developing white matter tracts and in cultured cells. Using chromatin immunoprecipitation (ChIP) and deep-sequencing in mouse and rat OPCs, we identified cell cycle genes (i.e., Cdc2) and chromatin components (i.e., Hmgn1, Hmgn2), including those modulating DNA methylation (i.e., Uhrf1), as E2F1 targets. Binding of E2F1 to chromatin on the gene targets was validated and their expression assessed in developing white matter tracts and cultured OPCs. Increased expression of E2F1 gene targets was also detected in mouse gliomas (that were induced by retroviral transformation of OPCs) compared with normal brain. Together, these data identify E2F1 as a key transcription factor modulating the expression of chromatin components in OPC during the transition from proliferation to differentiation.

Genetic polymorphism of the 26 short tandem repeat loci in the Chinese Hebei Han population using two commercial forensic kits.

We determined the allele frequencies and forensic parameters for the 26 short tandem repeat (STR) autosomal markers in two commercial kits (the Investigator HDplex and AmpFLSTR(®) Identifiler(®) systems) for 183 unrelated individuals from the Han population of the Hebei Province of China. The 26 STRs were all in Hardy-Weinberg equilibrium. No linkage disequilibrium was detected between any pair of loci. The combined power of discrimination and the combined power of exclusion for the 26 STR loci were 1-7.74E-31 and 1-1.21E-11, respectively. Six rare alleles of D10S2325 were identified and named 20, 21, 22, 23, 24, and 31. All the length of the six rare alleles were out of the range of allelic ladder. We calculated the population pairwise genetic distance based on the allele frequencies, using published population data including German, central Polish, south Dutch, northeastern Polish, south Brazilian, Korean, Sichuan Han of China, and Shanghai Han of China. Also we examined the population pairwise genetic distance of loci included in Identifiler system between Hebei Han and other ethnic population of China. These 26 autosomal STR loci could provide highly informative polymorphic data for paternity testing and forensic identification in the Hebei Han population in China. Because they are all in linkage equilibrium, they could be used together to solve deficient kinship cases or cases with mutations.

[The role of nuclear factor-κB in endothelial cell inflammatory injury by intermittent hypoxia in rat with emphysema].

OBJECTIVE: To investigate mechanism underlying the role of nuclear factor Kappa B (NF-κB) which induced inflammatory injury and functional lesions of aortic endothelial cells in rat with emphysema and intermittent hypoxia. METHODS: Sixty male Wistar rats were divided randomly into 4 experimental groups (n = 15 each group): control group, emphysema group, intermittent hypoxia (IH) group, emphysema with intermittent hypoxia group. The rats in control group had ad libitum access to food and water under normal circumstance. The rats in the emphysema group were exposed to cigarette smoke twice daily (30 min each time). As for IH group, the rats were exposed to intermittent hypoxia circumstance (8 h/day). Both cigarette smoke twice a day (30 min each time) and intermittent hypoxia circumstance (8 h/day) were imposed on the rats in emphysema with intermittent hypoxia group. All the rats were exposed for 8 weeks. Five rats were randomly selected from each group to measure the blood gas on the ninth week. We collected lung and endothelial tissues of thoracic aorta from the rest sacrificed rats, and observed the pathological changes of lung tissue through HE staining. The levels of ET-1, TNF-α and IL-8 in rat endothelial tissues of thoracic aorta were measured by ELISA testing. Nitrate reductase was used to measure the levels of NO, and RT-PCR to detect the levels of NF-κB mRNA, ICAM-1 mRNA, MMP-9 mRNA and eNOS mRNA. RESULTS: Lung pathology and blood gas results showed that the rat model of emphysema with intermittent hypoxia was established successfully. The levels of ET-1, TNF-α, IL-8 in emphysema with intermittent hypoxia group were (172.4 ± 1.6) ng/L, (104.1 ± 1.4) ng/L, (272.1 ± 3.6) ng/L respectively, significantly higher than the control group, emphysema group and intermittent hypoxia group (all P < 0.05). The level of NO was (27.07 ± 0.57) µmol/L, which was significant reduced; the expression of NF-κB mRNA, ICAM-1 mRNA, MMP-9 mRNA in emphysema with intermittent hypoxia group was significantly upregulated compared with the control goup, emphysema group and intermittent hypoxia group (all P < 0.05). The levels of eNOS mRNA expression were significantly lower than other three groups. The expression of NF-κB mRNA was positively correlated with MMP-9 mRNA level (r = 0.572, P < 0.001) and the expression of NF-κB mRNA was negatively correlated with eNOS mRNA level (r = 0.534, P < 0.001); there was no statistical difference in levels of NF-κB mRNA and eNOS mRNA expression between intermittent hypoxia and emphysema group (P > 0.05). CONCLUSION: Compared with only emphysema or intermittent hypoxia exposure, inflammatory injury of aortic endothelial cells of rats induced by emphysema with intermittent hypoxia was more serious, and may result in more serious cardiovascular complications. The activation of NF-κB pathway may be an important mechanism of its inflammatory response.

Single/multiple-mode-selection optical nanofilters based on end-coupled split-ring resonators.

A plasmonic mode-selection filter based on end-coupled circular split-ring resonators is proposed and demonstrated. In contrast to regular ring resonators, which can support only the integer modes, extra noninteger resonance modes will be excited by placing metallic nanowalls in the proposed circular ring resonators. Since all the modes are highly sensitive to the position of the nanowall, the associated modes are effectively excited or suppressed by manipulating the position. This proposed scheme offers great flexibility to design the transmission spectrum with expected modes. Moreover, each integer or noninteger resonance mode with high transmittance can be selected individually by cascading two proposed split-ring resonators that share an intersection of transmission peaks. The corresponding spectra and the propagation characteristics are numerically investigated by using the finite-difference time-domain method.