Microscopy Results Research Articles

Highly Dispersed ZnO Sites in a ZnO/ZrO2 Catalyst Promote Carbon Dioxide‐to‐Methanol Conversion

AbstractZnO/ZrO2 catalysts have shown better activity in the CO2 hydrogenation to methanol compared with single component counterparts, but the interaction between ZnO and ZrO2 is still poorly understood. In particular, the effect of the ZrO2 support phase (tetragonal vs. monoclinic) was not systematically explored. Here, we have synthesized ZnO/ZrO2 catalysts supported on tetragonal ZrO2 (ZnO/ZrO2‐t) and monoclinic ZrO2 (ZnO/ZrO2‐m), which resulted in the formation of different ZnOx species, consisting of sub‐nanometer ZnO moieties and large‐sized ZnO particles, respectively. ZnO/ZrO2‐t exhibited a higher methanol selectivity (81 vs. 39 %) and methanol yield (1.25 vs. 0.67 mmol g−1 h−1) compared with ZnO/ZrO2‐m. The difference in performance was attributed to the redox state and degree of dispersion of Zn, based on spectroscopy and microscopy results. ZnO/ZrO2‐t had a high density of ZnOx‐ZrOy sites, which favored the formation of active HCOO* species and enhanced the yield and selectivity of methanol along the formate pathway. Such ZnO clusters were further dispersed on ZrO2‐t during catalysis, while larger ZnO particles on ZnO/ZrO2‐m remained stable throughout the reaction. This study shows that the phase of ZrO2 supports can be used to control the dispersion of ZnO and the catalyst surface chemistry, and lead to enhanced catalytic performance.

Microstructure Evolution of Super304H Steel Used in a Service Power Station Boiler

The microstructure and structure of a Super304H superheater steel pipe after 47,000 h were analyzed by metallographic microscope, scanning electron microscope (SEM), and EDS, and its mechanical properties were measured by hardness meter. The results show that the austenitic grains appear on the outer wall of Super304H steel pipe after service, while the SEM and metallographic microscope tests show that the outer wall particles are coarse. There is an obvious corrosion layer on the outer surface, and the thickness of the corrosion layer on the windward surface is significantly higher than that on the leeward surface. The inner surface is refined and the hardness of the material is significantly increased; the outer surface, the inner surface, and the center all grow abnormally. In this case, the room temperature tensile strength and impact performance of the rough crystal area of the outer wall of the Super304H steel pipe are reduced and fracture along the crystal. Supervision should be strengthened to eliminate the safety risks caused by the abnormal growth of the outer wall austenite grain. The results of crystal phase microscopy show that the main structure of the material still maintains the basic structure of austenitic steel, and particle aggregation mainly occurs in the sub-inner layer of the inner and outer surface. Compared with the lee surface, the middle body structure is basically the same, but whether the thickness of the corrosion layer on the inner surface or the outer surface increases, the deformation degree of the deformation layer is greater. The hardness measurement finds that the hardness of the corrosion layer is caused by the increase in Super304H steel surface stress. In case of pipe explosion accident, the highest chance of pipe explosion here should be closely observed.

A green and efficient method to prepare oleic acid–modified CaCO3/reHDPE composites

Industrial recycling of waste plastics frequently utilizes mechanical recovery and recycling. However, plastics recycled through mechanical recovery tend to have reduced properties, limiting their applications. In this study, modified calcium carbonate (OA-CaCO3) was prepared using different amounts of oleic acid (OA) (0.5, 1.0, and 2.0 wt%). Infrared spectroscopic characterization showed OA was successfully adsorbed on the CaCO3 surface. Particle size, micromorphology, oil absorption value, and activation tests indicated that CaCO3 modified with 1.0 wt% OA yielded optimal results. Melt blending 1.0 wt% OA-modified CaCO3 with recycled high-density polyethylene (reHDPE) produced composites. Scanning electron microscopy results showed OA modification enhanced interfacial compatibility between the two phases. Mechanical property tests revealed at high filling levels, the impact strength of OA-modified composites increased considerably, reaching 42.6 kJ/m2 with 40 wt% OA-CaCO3 filling. Melt flow rate test results showed that OA-modified composites had increased melt flow and modified processing properties. Filling OA-CaCO3 to compensate for reHDPE properties caused by mechanical recycling is essential to expand mechanical recycling applications in plastics recycling.

Effect of Super Retarder on Recycled Water and Concrete Properties of Waste Slurry in Mixing Plant

A large amount of waste slurry water will be generated in the production process of concrete mixing plant, due to the complex composition of waste slurry water, if it is not handled in time when stored, serious coagulation will occur, which will accelerate the loss of equipment and reduce the utilization rate. In this paper, a super retarder suitable for waste slurry recycled water from concrete mixing plant was prepared using composite technology. The waste slurry recycled water mixed with super retarding agent was characterized by using microscopic testing means XRD, TG and DTG. The waste slurry recycled water mixed with super retarding agent was used to replace tap water in the production of concrete, and its effect on the workability and mechanical properties of concrete was investigated. It was found that the compounding of Butane 2-phospho-1,2,4-tricarboxylic acid (PBTCA) with Reclaimed water treatment agent (ACS) resulted in a setting time of 64 h for 10% concentration of recycled water, with optimal retarding effect. When PBTCA:ACS was 1:20, mixed at 1.5% of the mass of recycled water, the 1 h slump of concrete had no loss, the loss of extension was 15 mm, the 7 days compressive strength was increased by 3.5 MPa, and the 28 days compressive strength was increased by 3.0 MPa. The microscopic results showed that the use of ACS and PBTCA does not affect the type of cement hydration products, but only affects the the rate of hydration product generation.

Molecular beam epitaxy and band structures of type-II antiferromagnetic semiconductor EuTe thin films

The rare-earth Eu-based compounds with a unique half-filled 4f orbital have attracted an amount of research interest recently. Here, we synthesized EuTe(001) single-crystal thin films on SrTiO3(001) substrate via molecular beam epitaxy (MBE). The scanning tunneling microscopy and x-ray diffraction results indicate that the grown EuTe thin films orientated as EuTe[100]//SrTiO3[110] in plane. In the angle-resolved photoemission spectroscopic (ARPES) measurements, the grown EuTe films show a semiconductive band structure with the valence band maximum lying on the center point of the Brillouin zone. The bandgap size of EuTe was further identified by the optical transmission spectra as 2.2 eV. The antiferromagnetic transition temperature of the grown EuTe film is 10.5 K measured by a superconductive quantum interference device (SQUID). Our results provide important information on the fundamental electronic structures for the further research and applications of the Eu-based compounds.

AGOMELATINE ETHOSOMES FOR ENHANCED TRANSDERMAL DRUG DELIVERY

Objective: The current study aimed to prepare and optimize Agomelatine (AMN) ethosomes for enhanced transdermal drug delivery. Methods: In this study cold method was employed to manufacture the AMN-loaded ethosomes with dissimilar quantities of Phosphatidyl Choline (PC): Cholesterol: Ethanol. Transmission Electron Microscopy (TEM) was employed to evaluate the appearance of the formed ethosomes. Other formulation parameters like vesicle size and zeta potential, polydispersity index, transition temperature, and entrapment efficiency were also investigated. Results: The microscopy results showed that AMN ethosomes have a smooth surface. It was discovered that the AMN-3 formulation of transdermal ethosomes had 92.15±1.3 entrapment efficiency with good vesicle diameter. The release of agomelatine adhered to the zero-order release model. The polydispersity Index (PI) and zeta potential of the optimized formulation were found to be 0.209 and-14.09±1.95 mV, respectively. The maximum flux for the ethosome formulation (AMN-3) was 34.29 µg. h/cm2. A 10.71 fold increment was observed in the bioavailability of optimized formulation than control (oral suspension). A higher drug concentration in the blood suggested better systemic absorption of ethosomes. The optimized formula has a Tmax of 4.0±0.08h and 73.38±1.37 of Cmax. The AMN ethosomes were found to be more stable when stored at 4 °C. Conclusion: The current study suggests that ethosomal vesicles may improve transdermal dispersion without causing skin irritation. Agomelatine-loaded ethosome has the potential to be one of the most important transdermal application techniques for the treatment of depression.

Fabrication and application of a dual drug-loaded nanoniosomes encapsulating rutin and berberine: optimization, in vitro and ex vivo evaluation

Rutin and berberine are naturally occurring polyphenols but their usefulness is restricted by their low bioavailability and poor solubility. Thus, by delivering rutin–berberine in the form of niosomes simultaneously and hoped to enhance the permeability through nasal route for the treatment of depression. Thin-film hydration approach was used to generate dual drug-loaded niosomes (rutin–berberine) encapsulating rutin and berberine. Various analytical techniques were used to characterize the morphology, size, compatibility, and leakage of the particles. These techniques included transmission electron microscopy, dynamic light scattering, UV spectrophotometry, and differential scanning calorimetry. The optimized formulation (rutin–berberine optimized niosomal formulation) was subjected to additional characterization for drug release, ex-vivo penetration investigation, confocal laser scanning microscopy, and 2,2-diphenyl-1-picrylhydrazyl assay. The rutin–berberine optimized niosomal formulation analysis showed that the drug release was 76.66 ± 1.24% at 24 hours, the entrapment efficiency was 74.8 ± 2.13% (rutin), and 79.0 ± 3.47% (berberine) and the vesicle size was 72.6 nm with a polydispersion index of 0.208. The antioxidant activity showed 73.67 ± 2.5% which is close to regular ascorbic acid. Studies on permeation ex-vivo revealed that rutin–berberine optimized niosomal formulation had considerably higher permeation (84.89 ± 3.15%) compared to rutin–berberine suspension (37.28 ± 2.33%). Furthermore, rhodamine B-loaded rutin–berberine optimized niosomal formulation appeared to have higher penetration than the control (rhodamine B-solution) according to the confocal laser scanning microscope results of the nasal mucosa. Based on all the experimental data, rutin–berberine optimized niosomal formulations were determined to be a viable and successful intranasal delivery formulation.

PVDF‐based nanocomposite coatings with superhydrophobic and antibacterial properties on stainless steel surfaces

AbstractIn this study, using a spray‐coating technique, stainless steel surfaces were coated with polyvinylidene fluoride (PVDF) and carbon soot nanoparticles. We imparted various surface properties onto the coatings' surfaces by varying the nanoparticle content and the preparation method. The main aim was to develop antibacterial surfaces by inducing superhydrophobic properties in stainless steel surfaces. In a one‐step preparation method, 5% and 10% of nanoparticles were insufficient to achieve superhydrophobicity, whereas 20% significantly increased the water contact angle to 153°. Morphological evaluations revealed the formation of a nano‐scale structure, which also led to a staggering antibacterial rate of 99.5% against Listeria monocytogenes. Using a two‐step preparation, soot nanoparticles were localized at the coating's top layer, which led to superhydrophobicity at a lower nanoparticle content (10%). However, the bacterial adhesion study showed a lower antibacterial rate (~93%). The difference in bacterial adhesion results was explained by various roughness structures according to the atomic force microscopy results. The developed system has a promising potential to be used as self‐cleaning and antibacterial coatings in the medical and food industries.Highlights Stainless steel surfaces were coated with PVDF and carbon soot nanoparticles Imparted various surface properties onto the coatings' surfaces Developed antibacterial surfaces by inducing superhydrophobic properties Using a two‐step, soot nanoparticles were localized at the coating's top layer Bacterial adhesion study showed a lower antibacterial rate (~93%).

Properties of Steel Fiber Reinforced Desert Sand Concrete

To study the effect of steel fibers on the mechanical properties of desert sand concrete (DSC), three lengths (12 mm, 16 mm, and 20 mm) of steel fibers and five volumetric admixtures (0.4%, 0.8%, 1.2%, and 1.6%) of steel fibers were selected to make 13 groups of concrete specimens (78 cubic specimens and 39 prismatic specimens). Compressive test, splitting test and flexural test were carried out on the specimens of DSC after curing for 28 days. According to the test results, the influence law of each parameter on the mechanical properties of DSC was analyzed, and the working principle of steel fibers to improve the mechanical properties of DSC was described by combining macroscopic and microscopic methods. The results showed that the addition of steel fibers can effectively improve the damage pattern of DSC, and all the mechanical properties of DSC are improved; 12 mm steel fibers were relatively effective in enhancing the compressive strength of DSC and 20 mm steel fibers were relatively effective in enhancing the splitting and flexural strength of DSC; Both macroscopic and microscopic results showed that the addition of appropriate amount of steel fibers can effectively fill the internal pores of DSC. The results can provide theoretical basis and technical support for the engineering application of steel fiber reinforced DSC.

Green Synthesis of Platinum Nanoparticle Using Lemon (Citrus Limon) Peel Extract and its Characterization

Green synthesis of platinum nanoparticle using lemon peel extract is an alternative way to chemical synthesis of nanoparticles. This research was designed for the environmental friendly, pollution free, cost effective and has no side effects to the environment. The platinum nanoparticle was synthesized using (Citrus limon) lemon peel extract. Parameters such as time, pH, concentration, temperature and change in color from yellow to yellowish brown indicates the reduction of platinum ions which confirmed the synthesized platinum nanoparticle. The green synthesized platinum nanoparticle was further characterized by UV visible spectroscopy, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction Spectroscopy (XRD). The results of the UV spectroscopy revealed the reduction of platinum ions to platinum nanoparticle at the peak of 344 nm. The results of the Scanning Electron Microscopy confirmed the morphology of platinum nanoparticle which were smooth and spherical with a diameter of range from 71 to 90 nm at 41.0 kx magnification. The results of the Fourier Transform Infrared Spectroscopy revealed the strong broad band between 1095 to 3244.00 cm-1 which confirmed the presence of functional groups. X- ray diffraction (XRD) analysis confirmed the crystalline structure of synthesized platinum nanoparticle with the distinct peaks at 39.0°, 46.3° and 67.5°. Therefore the green synthesized platinum nanoparticle is an advantage to the environment than the chemical approaches. This technique is efficient and holds potential for various industrial applications and is sustainable.

Influence of starch on freeze-thaw stability of Hypophthalmichthys molitrix surimi gel observed via ice crystal distribution and gel properties

Starch has been recognized as a vital ingredient in surimi products due to its ability to absorb water, which reduces the deterioration of gels and water loss during freezing and thawing. However, it is essential to ascertain the role of starch in the formation of ice crystals and the texture of surimi gels. The impact of freeze-thaw cycles on the morphology and distribution of ice crystals, as well as the textural characteristics of gelatinized and ungelatinized starch-surimi gels was investigated. The results of light microscopy revealed that the presence of starch, irrespective of whether it was gelatinized, resulted in a reduction in the size of ice crystals within the surimi gel network during the freeze-thaw process. In addition, starch in surimi gels was subjected to freeze-thaw cycles, resulting in the emergence of two distinct states of bound water (0.1–1 ms and 1–10 ms). The higher relative content of immobile water indicated that the gelatinized starch had improved water holding properties. Furthermore, the incorporation of gelatinized starch into surimi enhanced its freeze-thaw stability and retarded the loss of gel strength, hardness, and whiteness. The addition of starch had a synergistic impact, enhancing the gel properties by affecting the formation of ice crystals and water absorption.

Analysis on the Influence law and Mechanism of the Strength of Reclaimed Aggregate-Industrial Waste Slag Solidified Silt

To optimize the usage of construction waste resources, industrial waste slag and silt, this paper used Portland cement, mineral waste residue and phosphogypsum composite to make cementing material (CMPS) with construction waste reclaimed aggregate to solidify silt. The laboratory solidification test and microscopic analysis were conducted to assess the mechanical characteristics of solidified sludge. In order to clarify the mineral composition, microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt (SS), XRD, SEM and nitrogen adsorption pore analyzer were employed for further explore the regenerated aggregate and CMPS solidified silt effectively, and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively. The findings indicated that the strength of Portland cementmineral waste residue phosphogypsum terpolymer system curing agent increased by 107.34% than that of single Port-land cement SS at 56 d, and the strength of CMPS solidified silt increased by 25.68% under the action of reclaimed aggregate framework. The maintenance period and water composition of the silt have high correlation with the strength. Therefore, influence law of above two influencing factors on its mechanical properties were further explored and the strength prediction were made. The microscopic test results showed that, drawing from the hydration of Portland cement and pozzolans reaction of mineral waste residue, the solidified system has pre-pared CaSiO3 hydrate gel and ettringite crystals with gelatinous properties, which help to fill the pores and form a denser structure.

Inhibitory effect of different degree of polymerization inulin on the retrogradation of rice starch gels and fresh rice noodles

This experiment investigated the effects of inulin (IN) with different degrees of polymerization at various addition levels on the water distribution, textural properties, microscopic and molecular structure, cooking quality, and sensory evaluation of rice starch (RS) and fresh rice noodles (FRN) during storage. The results showed that the addition of three kinds of IN significantly reduced the transverse relaxation time T2 of the starch gels system during storage, effectively combined the water molecules in the system. Meanwhile, the addition of IN reduced the increase of starch gels hardness during storage, inhibiting the retrogradation of the starch gels. Fourier transform infrared results further confirmed that IN could suppress the retrogradation behavior of starch during storage by controlling the rearrangement or recrystallization of starch molecular chains. The scanning electron microscopy results of FRN after 7 d of storage showed that the addition of IN enhanced the water retention capacity of FRN during the retrogradation process, which was consistent with the water distribution results. Furthermore, all three kinds of IN improved the cooking and sensory quality of FRN during storage, and the lower the degree of polymerization, the better the anti- retrogradation effect and the quality of the FRN.

Endogenous reactivation cases identified by whole genome sequencing of Mycobacterium tuberculosis: Exploration of possible causes in Latvian tuberculosis patients

BackgroundThe recurrence of tuberculosis (TB) continues to place a significant burden on patients and TB programs worldwide. Repeated TB episodes can develop either due to endogenous reactivation of previously treated TB or exogenous reinfection with a distinct strain of Mycobacterium tuberculosis (Mtb). Determining the precise cause of the recurrent TB episodes and identifying reasons for endogenous reactivation of previously successfully treated patients is crucial for introducing effective TB control measures. MethodsHere, we aimed to provide a retrospective individual analysis of the clinical data of pulmonary TB patients with assumed endogenous infection reactivation based on WGS results to identify the reasons for reactivation. Patient medical files were reviewed to describe the provoking factors for endogenous reactivation. ResultsIn total, 25 patients with assumed endogenous TB reactivation were included in the study group, and 30 patients with one TB episode during the study period were included in the control group. There were no statistically significant differences identified between studied patient groups in patients age (t(53) = −1.53, p = 0.13), body mass index (t(53) = 0.82, p = 0.42), area of residency (χ2(1;55) = 0.015, p = 0.9), employment status (χ2(1;55) = 0.076, p = 0.78) and presence of comorbidities (χ2(1;55) = 3.67, p = 0.78). Study group patients had statistically significantly more frequently positive sputum smear microscopy results (χ2(1;55) = 8.72, p = 0.0031), longer time to sputum smear (t(31) = −2.2, p = 0.036) and sputum culture conversion (W (55) = 198.5, p = 0.0029). Smoking was statistically significantly (χ2(1;55) = 5.77, p = 0.016) more frequently represented among study group patients. The median treatment duration for drug susceptible TB was 6 months in both in the control group (IQR 6–6) and among study group patients (IQR 6–7.75). The median treatment duration for multidrug-resistant TB was 20 months (IQR 17–23) in the control group and 19 months (IQR 16–19) in the study group patients. ConclusionPositive SSM for acid-fast bacteria, delayed time to sputum smear and sputum culture conversion, smoking, and incomplete therapy in the study group patients with multidrug-resistant TB should be considered as potential reasons for reactivation in recurrent TB patient group in our study.

Tearing properties, crystallization behavior, microstructure, and morphology of LLDPE with different short branched chain distributions

Abstract The length and distribution of comonomers with short-chain branching (SCB) have a significant influence on the crystallization behavior and crystal structure of polymers, as well as the mechanical properties of the material. This study investigates the crystallization behavior and properties of linear low-density polyethylene (LLDPE) samples with similar density, molecular weight, and branching degree but varying SCB distributions. The results show that LLDPE with butene as the comonomer has a stronger ability to suppress crystallization compared to LLDPE with hexene as the comonomer due to its more uniform SCB distribution. Additionally, among LLDPEs with comonomers of octene, hexene, and butene, the LLDPE with the most uniform SCB distribution exhibits the weakest crystallization ability. Small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) results indicate that LLDPE with more uniform distribution of SCB has smaller long-period and more regular lamellar structure. Therefore, LLDPE with more uniform SCB distribution exhibits weaker inhibition ability towards crystallization, leading to less agglomerated phases and weaker phase separation, resulting in higher tear strength.

Effect of carbon coating on improved electrical and electrochemical performance of Li3Co2SbO6

Abstract We reported a novel high voltage cathode having layered structure and manifold improvement (144%) in electrochemical performance on carbon coating Li3Co2SbO6. The carbon-coated Li3Co2SbO6 has been prepared using a high temperature solid-state method in an air medium with appropriate stoichiometry of the oxide and carbon source (sucrose). The x-ray diffraction and high-resolution transmission electron microscopy results have confirmed homogeneous carbon coating on oxide (Li3Co2SbO6) surface without disturbing phase, structure and morphology. The immediate effect of carbon coating resulted in electrical conductivity enhancement of the carbon coated Li3Co2SbO6 by four order of magnitudes ∼2.79 × 10−4 Scm−1 at room temperature vis-a-vis pristine Li3Co2SbO6. The electrochemical performance of the carbon coated Li3Co2SbO6 has shown sustainable improvement indicating redox activity by more than one Li+ transaction. The carbon coated Li3Co2SbO6 cathode exhibited an initial discharge capacity of 110 mAhg−1 compared to 45 mAhg−1 for its pristine counterpart. The improvement in electrochemical capacity on carbon coating, as reported in this work, is the highest ever compared to prior literature reports on Li3Co2SbO6.

Comparative analysis of airborne fungal spore distribution in urban and rural environments of Slovakia.

Monitoring airborne fungal spores is crucial for public health and plant production since they belong to important aeroallergens and phytopathogens. Due to different land use, their concentration can differ significantly between urban and rural areas. We monitored their spectrum and quantity on two geographically close sites with a different degree of urbanisation: Bratislava City and Kaplna Village in Slovakia, located 38km apart. We recorded the spectrum of airborne fungal spores over a year and confirmed the microscopic results by amplicon-based metagenomic analysis. The main spore season of the most frequent genera lasted over a week longer in Kaplna, but its intensity was approximately two-fold higher in Bratislava. This can be possibly connected to the microclimatic conditions of the urban area (especially wind speed and heat island effect) and the lesser use of fungicides. Cladosporium was the dominant genus on both sites, influencing the intensity most significantly. Through statistical analysis of the influence of meteorological parameters on airborne fungal spore levels, we identified a significant relationship with temperature, while the impact of other parameters varied depending on the spore type and release mechanism. Our results show the differences in airborne fungal spore levels between urban and rural areas and highlight the necessity for more monitoring stations in various environments.

Synthesis of Porous Carbons from Candlenut Shells Using Various Types of Activators for Environmentally Friendly Supercapacitors

Porous carbon is one of the promising electrode materials for supercapacitors due to its unique and engineerable microstructural properties. The study of the synthesis of porous carbon from waste biomass is very important due to the abundance of natural resources, low cost production and contribute to solving environmental problems. In this study, porous carbons derived from candlnut shell with various type of activator was studied the chemical structural, morphological and electrochemical properties then evaluated as electrodes for supercapacitor. We have been successfully synthesized of porous carbon from candlenut shells using three steps of the process, i.e.: carboni-zation, activation and calcination. Carbonization was carried out at 700°C in a furnace using a closed crucible to minimize the oxygen. The chemical activation conducted using three types of activators, i.e. ZnCl2, H3PO4 and KOH then calcination process by heated at 800°C for 1 h under Ar flow. The results of the Fourier-transform infrared (FTIR) analysis show that the carbonization process increases the content of aromatic C=C functional groups and reduce the OH, C-H, C-O and C=O functional groups. The carbonization process has also increased the electrical conductivity of the sample around 0.8525 S/m. The results of Scanning Electron Microscope (SEM) images can be observed that the activation process of carbon has formed which was indicated by the appearance of many pores on the surface area of carbon. N2 adsorption/desorption isotherms (Brunauer–Emmett–Teller (BET)) characterization was indicated that the porous carbon is dominated by mesoporous with a pore size around 2-50 nm. BET characterization also can be determined the surface area of porous carbon around 477 m2/g for ZnCl2, 636 m2/g for H3PO4, and 681 m2/g for KOH. This synthesized materials are further employed in a symmetric supercapacitor using simple glass cell. The best performance of supercapacitor achieved by KOH porous carbons with 16.30 F/g of specific capacitance, 2.26 Wh/kg of energy density and 1038 W/kg of power density.

Effect of Temperature and Electric Field Strength on Carrier Mobility of Oil-Impregnated Pressboard Under DC Voltage

The influence of carrier mobility on the space charge transport behavior inside the oil-impregnated pressboard insulation of converter transformers cannot be neglected. However, at present, current knowledge is usually derived from empirical or theoretical values, lacks experimental studies, and often ignores the effects of temperature and field strength under actual operating conditions. In this paper, based on the variable-temperature surface potential decay (SPD) method, a carrier mobility measurement platform for oil-impregnated pressboard is established, and the carrier mobility values for different combinations of oil and oil-impregnated pressboard are obtained experimentally to analyze and reveal the influence mechanisms of temperature and field strength on the carrier mobility. The results indicate the following: (1) The positive and negative carrier mobilities of oil-impregnated pressboard are in the range of 10−12–10−13 m2·V−1·s−1, and the negative carrier mobility is always higher than the positive carrier mobility. (2) The carrier mobility is positively correlated with the changes of temperature and field strength, and when the temperature increases from 20 °C to 80 °C, the positive and negative carrier mobilities increase by 4.01 times and 4.72 times, respectively; when the field strength increases from 1 kV/mm to 7 kV/mm, the positive and negative carrier mobility increases by 2.53 and 2.72 times, respectively. (3) The carrier mobility of the pressboard with a higher oil absorption rate changes more significantly with temperature; when the field strength is 7 kV/mm and the temperature increases from 20 °C to 80 °C, the positive polarity carrier mobility increases from 3.96 × 10−13 m2·V−1·s−1 to 2.64 × 10−11 m2·V−1·s−1, an increase of 66.67 times, while the increase in the carrier mobility of the pressboard with a lower oil absorption rate is only 1.59 times. (4) The carrier mobility of the naphthenic transformer oil-impregnated pressboard is higher than that of the paraffin-based transformer oil-impregnated pressboard, and the carrier mobility of two kinds of naphthenic transformer oil-impregnated pressboard is 3.16 times and 2.47 times higher than that of the paraffin-based transformer oil-impregnated pressboard, respectively, under the conditions of 60 °C and 7 kV/mm. (5) Utilizing the Darcy model and microscopic scanning results of the pressboard morphology, it was revealed that permeability and fiber structure are key factors influencing the variation in carrier mobility. The research results of this paper can provide theoretical basis for the calibration and optimization of the oil-pressboard insulation structure of converter transformers.

Cytospora azadirachtae sp. nov.—A new species associated with dieback disease in Azadirachta indica from southern India

Stem cankers associated with dieback disease of neem (Azadirachta indica) shoots were collected from Manasagangotri and Doddamaragowdanahalli, Mysore, Karnataka (India) and based on microscopic, cultural and initial blast results of ITS-rDNA identified the isolated fungus to the genus Cytospora. The phylogenetic analysis based on nrITS-rDNA-tef1-α-tub2 sequence data showed it represents a new species and is described as Cytospora azadirachtae. The concatenated phylogeny revealed that Cytospora azadirachtae is phylogenetically distinct and closely related to Cytospora shoreae and C. rhizophorae. Cytospora rhizophorae differs from C. azadirachtae in that it has shorter conidia and conidiogenous cells. Further, C. rhizophorae is halotolerant and saprobic and shows host-specificity usually associated with Rhizophora sp. (R. mangle and R. mucronata). Similarly, C. shoreae differs from C. azadirachtae in having larger flask-shaped conidiomata and larger conidia. Based on multi-locus sequence and phylogenetic analysis of the canker and dieback disease symptoms, the present study introduces C. azadirachtae as a new species.