30 research outputs found
Black carbon: Atmospheric measurements and radiative effect.
No full textAtmospheric black carbon concentrations have been measured in air, cloud, rain and snow samples collected over Nova Scotia during the Radiation, Aerosol, Cloud Experiment (RACE) of 1995. Atmospheric aerosol samples for black carbon analyses were collected by filtering a known amount of air or liquid dispersons (cloud water, rain or melted snow) through quartz filters, and the filters were later subjected to thermo-optical analyses for black carbon determination. The average black carbon atmospheric concentration found in air was \rm 0.13\pm 0.01\mu g/m\sp3 at an altitude between 100 and 1700m: \rm 0.22 \pm 0.02\mu g/m\sp3 at near-sea surface; and \rm 0.54 \pm 0.03\mu g/m\sp3 in summer and \rm 1.69 \pm 0.08\mu g/m\sp3 in winter over Halifax area. The black carbon to SO\sb4\sp{-2} mass mixing ratio was found to be 14% over all the samples collected during RACE and the typical black carbon mass fraction in total aerosol is 1-2%. About 6% of black carbon was in the form of an internal mixture inside cloud droplets. The average black carbon content found in cloud water was about g/kg. The average black carbon content was g/kg in rain, and g/kg in snow over all the samples collected in both rural and urban areas.The radiative effect of black carbon is discussed in the present study. The black carbon radiative effect is significant compared with sulfate aerosol effect. Black carbon aerosols act to reduce the cooling effect of sulfate aerosols. The reduction of the cooling depends on both the black carbon fraction and the surface albedo. For instances of high surface albedo or high black carbon loading a net heating can result. The results for the Quebec forest fire day show that the black carbon aerosol decreases the sulfate aerosol cooling effect by 20 to 50%. The impact of black carbon aerosol on the radiative properties of clouds is insignificant over the Nova Scotia region.Thesis (Ph.D.)--Dalhousie University (Canada), 1996
Development of new methods for analyzing lipid oxidation: accelerated solvent extraction and HPLC-DNPH analyses of carbonyl oxidation products
No full textThe basic reactions of lipid oxidation were first reported more than 50 years ago, yet accurate and reproducible measurement of lipid oxidation remains a serious problem and challenge for both industry and academia. This research addresses two critical issues in lipid oxidation measurements: 1) lack of extraction methods that do not induce adventitious oxidation or change existing oxidation products; 2) lack of sensitive reproducible methods for quantitating and identifying secondary non-volatile oxidation products such as carbonyls, core aldehydes in particular. This research aims to develop two reliable, sensitive and accurate methods for oxidation analyses: 1) a pressurized solvent extraction method that is efficient in removing lipid yet does not add to or destroy lipid oxidation products, and 2) an improved HPLC-DNPH assay to quantitate and identify soluble carbonyl oxidation products in individual lipid fractions. Baked pet food biscuits and dry extruded pet food kibbles were chosen as samples to conduct lipid extraction in pressurized accelerated solvent extractor (ASE) by adjusting a variety of factors such as temperature, sample particle size, polarity of extraction solvent, extraction static time and numbers of extraction cycles to investigate the effect of extraction conditions on lipid oxidation. Results showed extraction with two 15-minute cycles of chloroform:methanol at 40 C gave lipid yields of 75-100%, depending on the kibble. Lipid oxidation was minimal when temperature was limited to 40 C. Factors such as particle size, solvents and extraction static time and cycles could be combined and tailored to optimize extraction efficiency. Compared to traditional extraction methods, pressurized solvent extraction of lipids was significantly more efficient and induced less oxidation. A reverse phase HPLC-DNPH (2,4-dinitrophenylhydrazine) assay capable of quantitating and identifying carbonyls in all lipid classes was developed using an acetonitrile–isopropanol-water gradient and diode array detection at 360 nm. Optical response decreased with fatty acid chain length; quantitation was achieved using average slopes for three size ranges. The assay was specific for carbonyls and detected 6-50 g/L and accurately quantitated 20 g/L standard aldehydes. LC-MS/MS Q-TOF verified hydrazone structures. Monomer carbonyls and core aldehydes were distinguished and quantitated in oxidized Trilinolein, commercial oils, and lipid extracts.Ph.D.Includes bibliographical referencesby Linhong Ya
Binuclear iron-sulfur complexes with bidentate phosphine ligands as active site models of Fe-hydrogenase and their catalytic proton reduction
No full textThe displacement of CO in a few simple Fe(I)-Fe(I) hydrogenase model complexes by bisphosphine ligands Ph2P-(CH2)(n)-PPh2 [with n = 1 (dppm) or n = 2 (dppe)] is described. The reaction of [{mu-(SCH2)(2)CH2}Fe-2(CO)(6)] (1) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(6)] (2) with dppe gave double butterfly complexes [{mu-(SCH2)(2)CH2}Fe-2(CO)(5)(Ph2PCH2)](2) (3) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(5)(Ph2PCH2)](2) (4), where two Fe2S2 units are linked by the bisphosphine. In addition, an unexpected byproduct, [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(5){Ph2PCH2CH2(Ph2PS)}] (5), was isolated when 2 was used as a substrate, where only one phosphorus atom of dppe is coordinated, while the other has been converted to PS, presumably by nucleophilic attack on bridging sulfur. By contrast, the reaction of 1 and 2 with dppm under mild conditions gave only complexes [{mu-(SCH2)(2)CH2}Fe-2(CO)(5)(Ph2PCH2PPh2)] (6) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(5)(Ph2PCH2PPh2)] (8), where one ligand coordinated in a monodentate fashion to one Fe2S2 unit. Furthermore, under forcing conditions, the complexes [{mu-(SCH2)(2)CH2}Fe-2(CO)(4){mu-(Ph2P)(2)CH2}] (7) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(4){mu-(Ph2P)(2)CH2}] (9) were formed, where the phosphine acts as a bidentate ligand, binding to both the iron atoms in the same molecular unit. Electrochemical studies show that the complexes 3, 4, and 9 catalyze the reduction of protons to molecular hydrogen, with 4 electrolyzed already at -1.40 V versus Ag/AgNO3 (-1.0 V vs NHE).</p
SHLUT: Efficient Image Enhancement using Spatial-Aware High-Light Compensation Look-up Tables
No full textRecently, the look-up table (LUT)-based method has achieved remarkable success in image enhancement tasks with its high efficiency and lightweight nature. However, when considering edge scenarios with limited computational resources, most existing methods fail to meet practical requirements due to their costly floating-point operations on convolution layers, which limit their general use. Moreover, most LUT-based methods may not perform well in handling high-light regions. To address these issues, we propose SHLUT, an efficient and practical image enhancement method by using spatial-aware high-light compensation look-up tables (LUTs), which comprise two parts. Firstly, we propose a spatial-aware weight predictor to reduce the computational burden. A lightweight network is trained to predict spatial-aware weight values, and then we transfer the values to the LUTs. Additionally, to correct overexposure in high-light regions, we propose a high-light compensation 3D LUT. Our proposed method allows us to directly retrieve the values from the LUTs to achieve efficient image enhancement at test time. Extensive experimental results demonstrate that SHLUT exhibits competitive performance compared to other LUT-based methods both quantitatively and qualitatively in a more efficient manner. For instance, SHLUT significantly reduces computational resources (at least 18 times in GFLOPs compared to other LUT-based methods), while excelling in high-light region handling.Computer Graphics ForumFix it in Post: Image and Video Synthesis and Analysis44
Synthesis and Antibacterial Evaluation of N-phenylacetamide Derivatives Containing 4-Arylthiazole Moieties
No full textA series of new N-phenylacetamide derivatives containing 4-arylthiazole moieties was designed and synthesized by introducing the thiazole moiety into the amide scaffold. The structures of the target compounds were confirmed by 1H-NMR, 13C-NMR and HRMS. Their in vitro antibacterial activities were evaluated against three kinds of bacteria—Xanthomonas oryzae pv. Oryzae (Xoo), Xanthomonas axonopodis pv. Citri (Xac) and X.oryzae pv. oryzicola (Xoc)—showing promising results. The minimum 50% effective concentration (EC50) value of N-(4-((4-(4-fluoro-phenyl)thiazol-2-yl)amino)phenyl)acetamide (A1) is 156.7 µM, which is superior to bismerthiazol (230.5 µM) and thiodiazole copper (545.2 µM). A scanning electron microscopy (SEM) investigation has confirmed that compound A1 could cause cell membrane rupture of Xoo. In addition, the nematicidal activity of the compounds against Meloidogyne incognita (M. incognita) was also tested, and compound A23 displayed excellent nematicidal activity, with mortality of 100% and 53.2% at 500 μg/mL and 100 μg/mL after 24 h of treatment, respectively. The preliminary structure-activity relationship (SAR) studies of these compounds are also briefly described. These results demonstrated that phenylacetamide derivatives may be considered as potential leads in the design of antibacterial agents
Synthesis and Antibacterial Evaluation of Novel 1,3,4-Oxadiazole Derivatives Containing Sulfonate/Carboxylate Moiety
No full textIn order to discover new lead compounds with high antibacterial activity, a series of new derivatives were designed and synthesized by introducing a sulfonate or carboxylate moiety into the 1,3,4-oxadiazole structure. Antibacterial activity against two phytopathogens, Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac), was assayed in vitro. The preliminary results indicated that ten compounds including 4a-1-4a-4 and 4a-11-4a-16 had good antibacterial activity against Xoo, with EC50 values ranging from 50.1-112.5 µM, which was better than those of Bismerthiazol (253.5 µM) and Thiodiazole copper (467.4 µM). Meanwhile, 4a-1, 4a-2, 4a-3 and 4a-4 demonstrated good inhibitory effect against Xanthomonas axonopodis pv. citri with EC50 values around 95.8-155.2 µM which were better than those of bismerthiazol (274.3 µM) and thiodiazole copper (406.3 µM). In addition, in vivo protection activity of compound 4a-2 and 4a-3 against rice bacterial leaf blight was 68.6% and 62.3%, respectively, which were better than bismerthiazol (49.6%) and thiodiazole copper (42.2%). Curative activity of compound 4a-2 and 4a-3 against rice bacterial leaf blight was 62.3% and 56.0%, which were better than bismerthiazol (42.9%) and thiodiazole copper (36.1%). Through scanning electron microscopy (SEM) analysis, it was observed that compound 4a-2 caused the cell membrane of Xanthomonas oryzae pv. oryzae ruptured or deformed. The present results indicated novel derivatives of 5-phenyl sulfonate methyl 1,3,4-oxadiazole might be potential antibacterial agents
Design, Synthesis and Bioactivity of Novel Pyrimidine Sulfonate Esters Containing Thioether Moiety
No full textPesticides play an important role in crop disease and pest control. However, their irrational use leads to the emergence of drug resistance. Therefore, it is necessary to search for new pesticide-lead compounds with new structures. We designed and synthesized 33 novel pyrimidine derivatives containing sulfonate groups and evaluated their antibacterial and insecticidal activities. Results: Most of the synthesized compounds showed good antibacterial activity against Xanthomonas oryzae pv. Oryzae (Xoo), Xanthomonas axonopodis pv. Citri (Xac), Pseudomonas syringae pv. actinidiae (Psa) and Ralstonia solanacearum (Rs), and certain insecticidal activity. A5, A31 and A33 showed strong antibacterial activity against Xoo, with EC50 values of 4.24, 6.77 and 9.35 μg/mL, respectively. Compounds A1, A3, A5 and A33 showed remarkable activity against Xac (EC50 was 79.02, 82.28, 70.80 and 44.11 μg/mL, respectively). In addition, A5 could significantly improve the defense enzyme (superoxide dismutase, peroxidase, phenylalanine ammonia-lyase and catalase) activity of plants against pathogens and thus improve the disease resistance of plants. Moreover, a few compounds also showed good insecticidal activity against Plutella xylostella and Myzus persicae. The results of this study provide insight into the development of new broad-spectrum pesticides
Antifungal Mechanism of Phenazine-1-Carboxylic Acid against Pestalotiopsis kenyana
No full textPestalotiopsis sp. is an important class of plant pathogenic fungi that can infect a variety of crops. We have proved the pathogenicity of P. kenyana on bayberry leaves and caused bayberry blight. Phenazine-1-carboxylic acid (PCA) has the characteristics of high efficiency, low toxicity, and environmental friendliness, which can prevent fungal diseases on a variety of crops. In this study, the effect of PCA on the morphological, physiological, and molecular characteristics of P. kenyana has been investigated, and the potential antifungal mechanism of PCA against P. kenyana was also explored. We applied PCA on P. kenyana in vitro and in vivo to determine its inhibitory effect on PCA. It was found that PCA was highly efficient against P. kenyana, with EC50 around 2.32 μg/mL, and the in vivo effect was 57% at 14 μg/mL. The mechanism of PCA was preliminarily explored by transcriptomics technology. The results showed that after the treatment of PCA, 3613 differential genes were found, focusing on redox processes and various metabolic pathways. In addition, it can also cause mycelial development malformation, damage cell membranes, reduce mitochondrial membrane potential, and increase ROS levels. This result expanded the potential agricultural application of PCA and revealed the possible mechanism against P. kenyana
Unexpected Tandem Reactions of Tris(cyclopentadieny1)lanthanide with Diphenylketene and Regeneration of the η<sup>5</sup>-Bonding Mode: One-Pot Synthesis of Heteroleptic Yttrocenes from Simple (C<sub>5</sub>H<sub>5</sub>)<sub>3</sub>Y Precursors
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