35 research outputs found
Dcc Regulates Asymmetric Outgrowth of Forebrain Neurons in Zebrafish
The guidance receptor DCC (deleted in colorectal cancer) ortholog UNC-40 regulates neuronal asymmetry development in Caenorhabditis elegans, but it is not known whether DCC plays a role in the specification of neuronal polarity in vertebrates. To examine the roles of DCC in neuronal asymmetry regulation in vertebrates, we studied zebrafish anterior dorsal telencephalon (ADt) neuronal axons. We generated transgenic zebrafish animals expressing the photo-convertible fluorescent protein Kaede in ADt neurons and then photo-converted Kaede to label specifically the ADt neuron axons. We found that ADt axons normally project ventrally. Knock down of Dcc function by injecting antisense morpholino oligonucleotides caused the ADt neurons to project axons dorsally. To examine the axon projection pattern of individual ADt neurons, we labeled single ADt neurons using a forebrain-specific promoter to drive fluorescent protein expression. We found that individual ADt neurons projected axons dorsally or formed multiple processes after morpholino knock down of Dcc function. We further found that knock down of the Dcc ligand, Netrin1, also caused ADt neurons to project axons dorsally. Knockdown of Neogenin1, a guidance receptor closely related to Dcc, enhanced the formation of aberrant dorsal axons in embryos injected with Dcc morpholino. These experiments provide the first evidence that Dcc regulates polarized axon initiation and asymmetric outgrowth of forebrain neurons in vertebrates
Development of a Polyacrylate/Silica Nanoparticle Hybrid Emulsion for Delaying Nutrient Release in Coated Controlled-Release Urea
Polyacrylate/silica hybrid emulsions were prepared by blending aqueous silica nanoparticles with polyacrylate emulsion, which were used for coating urea granules. After incorporating 1.0 wt.% silica nanoparticles into polyacrylate emulsion, preliminary solubility of CRU was decreased from 38.3% to 2.2%, and the release duration was extended from 8 to 27 days. The hybrid coating remarkably delayed the release of urea via improving wear-resistance due to the enhanced hardness, reducing water vapor permeability because of the tortuous diffusion pathway, and less breakage of CRU granules resulted from higher glass transition temperature. Meanwhile, the processibility was improved, which prevented particle agglomeration during coating. Therefore, aqueous silica nanoparticles have potential application in polymer emulsion coated controlled-release fertilizers
Analysis of segregation solute redistribution and centerline in continuously cast thin slab
A model has been built to calculate the solute redistribution in continuously cast thin slab and the effect of the fluid flow in mush on the centerline segregation was analyzed. The corresponding simulation program was developed by applying the SIMPLER algorithm. The momentum, energy and species conservation equations were solved simultaneously. The macro-segregation of a 3-D thin slab with 900 mm x 50 mm cross section was simulated. The obtained results show that negative segregation forms near the slab surface and severe centerline segregation forms in the mid-thickness plane. The species concentration in the centerline of the slab increases obviously at the final solidification stage
Application of Graphene-Oxide-Modified Polyacrylate Polymer for Controlled-Release Coated Urea
Polyacrylate polymer (PA) was modified with graphene oxide (GO) and the obtained composites were applied as coatings for controlled-release coated urea (CRU). The physicochemical properties of the different PA/GO coatings were characterized in detail and the nitrogen-release characteristics of the obtained CRU samples were determined in water at 25 °C. The experimental results revealed that addition of GO to PA reduced the swelling degree from 83.01% to 46.35% and improved its mechanical properties (the Young’s modulus was improved from 31.52 to 34.97 MPa and the glass transition temperature was increased from 4.21 to 6.11 °C), thus dramatically slowing down the cumulative nutrient release from the CRU fertilizer from 87.25% to 59.71%. These results suggest that GO enhances the properties of PA for CRU applications, which shows that GO-modified PA is a good coating material
Rapid and Nondestructive Detection of Pesticide Residues by Depth-Profiling Fourier Transform Infrared Photoacoustic Spectroscopy
Fast and Simultaneous Determination of Soil Properties Using Laser-Induced Breakdown Spectroscopy (LIBS): A Case Study of Typical Farmland Soils in China
Accurate management of soil nutrients and fast and simultaneous acquisition of soil properties are crucial in the development of sustainable agriculture. However, the conventional methods of soil analysis are generally labor-intensive, environmentally unfriendly, as well as time- and cost-consuming. Laser-induced breakdown spectroscopy (LIBS) is a “superstar” technique that has yielded outstanding results in the elemental analysis of a wide range of materials. However, its application for analysis of farmland soil faces the challenges of matrix effects, lack of large-scale soil samples with distinct origin and nature, and problems with simultaneous determination of multiple soil properties. Therefore, LIBS technique, in combination with partial least squares regression (PLSR), was applied to simultaneously determinate soil pH, cation exchange capacity (CEC), soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available phosphorus (AP), and available potassium (AK) in 200 soils from different farmlands in China. The prediction performances of full spectra and characteristic lines were evaluated and compared. Based on full spectra, the estimates of pH, CEC, SOM, TN, and TK achieved excellent prediction abilities with the residual prediction deviation (RPDV) values > 2.0 and the estimate of TP featured good performance with RPDV value of 1.993. However, using characteristic lines only improved the predicted accuracy of SOM, but reduced the prediction accuracies of TN, TP, and TK. In addition, soil AP and AK were predicted poorly with RPDV values of < 1.4 based on both full spectra and characteristic lines. The weak correlations between conventionally analyzed soil AP and AK and soil LIBS spectra are responsible for the poor prediction abilities of AP and AK contents. Findings from this study demonstrated that the LIBS technique combined with multivariate methods is a promising alternative for fast and simultaneous detection of some properties (i.e., pH and CEC) and nutrient contents (i.e., SOM, TN, TP, and TK) in farmland soils because of the extraordinary prediction performances achieved for these attributes
Degradation of Polyacrylate in the Outdoor Agricultural Soil Measured by FTIR-PAS and LIBS
Recently, polyacrylates (PA) have been applied in coated controlled-release fertilizer (CRF), but the impacts of the soil on the degradation of PA have not been evaluated. In this study, an outdoor agriculture soil buried test was carried out for 12 months to investigate the degradation of PA films. The residual degraded films were taken regularly from the soil and analyzed by SEM, Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) and laser-induced breakdown spectroscopy (LIBS). The concentration of C⁻H and C=O molecular groups of PA were decreased, and the element concentrations of C, O, K, Si of PA were increased under the degradation process. The surface of PA became rough and the degradation of PA occurred on the surface layer. Principal component analysis (PCA) showed that soil invaded PA. The results indicated that PA were environmentally friendly when applied to CRF. FTIR-PAS and LIBS were advanced in the in-situ surface analysis of the degradation process of the polymer
Degradation of Metal-Organic Framework Materials as Controlled-Release Fertilizers in Crop Fields
The behavior of a metal-organic framework (MOF) compound synthesized in hydrothermal reaction conditions and rich in N, P, and Fe nutrients was explored in the field. The attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and laser induced breakdown spectroscopy (LIBS) characterization results showed that the chemical structures changed during the degradation process in crop field soil. The scanning electron microscope images showed that the micro-rod of the MOF peeled off and degraded in layers. During the growth period of wheat, the MOF degraded by 50.9%, with the degradation rate being closely related to soil temperature. It was also found that the degradation rate increased with soil temperature. Moreover, the nutrient concentration of the soil indicated that the MOF had stable nutrients release efficiencies and could provide a continuous supply of nutrients throughout the wheat growth period, which showed a great alternative for MOF as a fertilizer both benefiting agricultural production and environmental protection
Application of Nano Fe<sup>III</sup>–Tannic Acid Complexes in Modifying Aqueous Acrylic Latex for Controlled-Release Coated Urea
Acrylic
latexes are valuable waterborne materials used in controlled-release
fertilizers. Controlled-release urea coated with these latexes releases
a large amount of nutrients, making it difficult to meet the requirement
of plants. Herein, Fe<sup>III</sup>–tannic acid (TA) complexes
were blended with acrylic latex and subsequently reassembled on a
surface of polyacrylate particles. These complexes remarkably retarded
the release of urea (the preliminary solubility was decreased from
22.3 to 0.8%) via decreasing the coating tackiness (<i>T</i><sub>g</sub> was increased from 4.17 to 6.42 °C), increasing
the coating strength (tensile stress was improved from 3.88 to 4.45
MPa), and promoting the formation of denser structures (surface tension
was decreased from 37.37 to 35.94 mN/m). Overall, our findings showed
that a simple blending of Fe<sup>III</sup>–TA complexes with
acrylic latex produces excellent coatings that delay the release of
urea, which demonstrates great potential for use in controlled-release
fertilizers coated with waterborne polymers
Transcriptome response to copper heavy metal stress in hard-shelled mussel (Mytilus coruscus)
The hard-shelled mussel (Mytilus coruscus) has considerably one of the most economically important marine shellfish worldwide and considered as a good invertebrate model for ecotoxicity study for a long time. In the present study, we used Illumina sequencing technology (HiSeq2000) to sequence, assemble and annotate the transcriptome of the hard-shelled mussel which challenged with copper pollution. A total of 21,723,913 paired-end clean reads (NCBI SRA database SRX1411195) were generated from HiSeq2000 sequencer and 96,403 contigs (with N50Â =Â 1118Â bp) were obtained after de novo assembling with Trinity software. Digital gene expression analysis reveals 1156 unigenes are upregulated and 1681 unigenes are downregulated when challenged with copper. By KEGG pathway enrichment analysis, we found that unigenes in four KEGG pathways (aminoacyl-tRNA biosynthesis, apoptosis, DNA replication and mismatch repair) show significant differential expressed between control and copper treated groups. We hope that the gill transcriptome in copper treated hard-shelled mussel can give useful information to understand how mussel handles with heavy metal stress at molecular level. Keywords: Hard-shelled mussel, Heavy metal, Transcriptome, Ecotoxicit