A single-electron tunneling model: a theoretical analysis of a metal nanoparticle-doped epoxy resin to suppress surface charge accumulation on insulators subjected to DC voltages.

In high-voltage direct current transmission systems, charges accumulate at the gas-solid interface, distorting the local field strength, causing a reduction in the flashover voltage, and threatening the safe and reliable operation of the power system. The latest research has found that doping metal nanoparticles into an epoxy resin effectively suppresses the surface charge accumulation on insulators and improves their flashover voltage. This paper further analyzes the microscopic mechanism of this phenomenon, establishes a single-electron tunneling mode, and draws two conclusions: when there is no agglomeration of the doped nanoparticles, a higher doping concentration can be achieved, which provides a better insulative performance. The optimal metal nanoparticle radius is several to tens of nanometers. This work provides theoretical guidance for the future improvement of insulating materials through metal nanoparticle doping and has good prospects in engineering applications.

Metal nanoparticle-doped epoxy resin to suppress surface charge accumulation on insulators under DC voltage.

In high-voltage direct current (HVDC) transmission systems, electric charge accumulates on insulator surfaces, causing surface electric field distortion and flashover voltage reduction. Therefore, studying a material that can improve the insulator surface insulation strength is of great engineering value. In this work, several types of metal nanoparticles with different particle sizes and concentrations are doped into epoxy resin. The experimental phenomena enables some interesting conclusions: when no agglomeration of doped nanoparticles occurs, a higher doping concentration provides a better insulation performance. The larger the doping particle size is, the lower the insulation performance. Additionally, under the same conditions, different types of metal nanoparticles lead to slightly different results after doping. Especially after doping with low concentration (approximately 120 parts per million (ppm)) and small particle size (approximately 10 nm) nanocopper particles, the insulator surface charge accumulation was effectively suppressed, and the flashover voltage was significantly improved. Our analysis suggests that it may be related to the single-electron tunneling phenomenon. Relevant results provide a new way to improve the surface insulation strength of insulators in the future.

Anti-malarial activity of new N-acetyl-L-leucyl-L-leucyl-L-norleucinal (ALLN) derivatives against Plasmodium falciparum.

Malaria is the most common of the parasitic diseases in tropical and subtropical regions. Adverse side effects of anti-malarial drugs have precluded them as a potential clinical drug. In this study, novel derivatives of N-acetyl-L-leucyl-L-leucyl-L-norleucinal (ALLN) based on a variety of dipeptidyl α,ß-unsaturated amides containing lysine as a part were synthesized and evaluated. Lower toxicity was achieved by reducing or eliminating the tendency of forming chemically reactive and toxic intermediates and metabolites. The synthesized compounds were evaluated for anti-malarial efficacy against Plasmodium falciparum and cytotoxicity in human epitheloid carcinoma cervix (HeLa cells) by estimating the therapeutic index (TI). N-Methyl amide with N'-Boc protection among them exhibited strong anti-malarial activity and N-methyl amide with N'-m-methylbenzyl amide showed excellent anti-malarial activity with much lower toxicity than the ALLN. Therefore, the two chemicals, as well as the underlying design rationale, could be useful in the discovery and development of new anti-malarial drugs.

Synthesis and evaluation of peptidyl α,ß-unsaturated carbonyl derivatives as anti-malarial calpain inhibitors.

Malarial calpain is a cysteine protease believed to be a central mediator essential for parasitic activities. N-Acetyl-L-leucyl-L-leucyl-L-norleucinal (ALLN), a calpain inhibitor, showed an excellent inhibitory effect on the erythrocytic stages of Plasmodium falciparum. However the aldehyde group of ALLN makes it susceptible to metabolism. Therefore, we designed α,ß-unsaturated carbonyl peptides that could serve as electrophiles for cysteine residues in calpain. Among the synthetic analogs based on the structure of ALLN, peptidyl esters 7, 8 and 9 showed the most potent anti-malarial effects, with the same IC50 values of 5.0 µM. Also they showed the high selective toxicity for the malaria versus Hela cell with 40.6, 69.2 and 24.3 fold for 7, 8 and 9, respectively. Dipeptidyl α,ß-unsaturated carbonyl derivatives consisting of two amino acids gave better anti-malarial effects than those consisting with one amino acid. The fluctuation in anti-malarial activity with small changes in chemical structure indicates the possibilities of improving synthetic analogs.

[Genetic potential analysis of six tilapia populations by microsatellite DNA markers].

Twenty five microsatellite loci were used to analyze two blue tilapia populations ["Xia'ao 1" (ZA), Guangxi population] and four nile tilapia populations [Egypt strain (ZN), 88 strain (XN), Guangxi population (GN), American strain (MN)]. A total of 7775 fragments ranging from 100 bp to 400 bp in length were obtained. Three to eight alleles were amplified in 25 loci and 143 alleles in all the six populations. The average number of alleles in each locus was 5.72. The average values of observed heterozygosity (Ho) ranged from 0.7253 to 0.8160, the average expected heterozygosity (He) ranged from 0.5146 to 0.6834, the average polymorphic information content (PIC) ranged from 0.4212 to 0.6105, and the number of average effective alleles (Ae) ranged from 2.20 to 3.23. The highest genetic similarity index was 0.9130 (between ZA and GA); and the lowest was 0.4352 (between ZA and ZN). The results showed that the four nile tilapia populations contained a high level of genetic potential, and the two blue tilapia populations were moderate.

Development of 10 tri- and tetranucleotide microsatellite loci for population studies in the common carp (Cyprinus carpio L.).

Ten tri- and tetranucleotide microsatellite DNA markers were isolated and characterized from common carp (Cyprinus carpio L.) to estimate genetic potential. These markers were tested in the samples from two closely related carp populations (Cyprinus carpio var. xingguonensis and Cyprinus carpio var. wananensis). The number of the alleles ranged from three to nine, and observed and expected hererozygosities varied from 0.207 to 1.000 and from 0.499 to 0.900 in each population, respectively. No evidence for linkage disequilibrium was found, indicating that these markers will be useful for population studies.

[Genetic potential analysis of Germany mirror carp (Cyprinus carpio L.) using microsatellite markers].

Using 30 microsatellite markers and combining quantity characters such as body weight, body size and body width, we evaluated the genetic potential of 3 Germany mirror carp populations. Number of effective alleles (Ae), observed (Ho) and expected (He) heterozygosity values and polymorphic information contents (PIC) were all calculated. 287 alleles and 559 genotypes were detected. The DNA fragment length was 109-400 bp. The Hardy-Weinberg Equilibrium was checked and phenomenon of some disequilibrium were studied according to the test of c2. The result showed that the level of genetic variability was moderate, but genetic potential of Shuanglai population was much lower than that Huanxin and Songpu breeding populations. Polymorphic Information Contents (PIC) of the 3 populations of Germany mirror carp were between 0.08787 and 0.5377, both of highly and moderately polymorphic markers were 13. The number of effective alleles (Ae) were between 1.1014 and 6.4665. The observed (Ho) and expected (He) heterozygosity values were 0.0968-0.9892 and 0.0926-0.8554 respectively. The linkage correlation was analyzed using data of body weight, body size and body width and 30 loci. The result shown that there existed 2 loci, HLJ319 and HLJ693 associated with body size. The HLJ693 locus significantly correlated with body weight character. The HLJ677 locus linked with body width. And then the result were verified in Recombinant Inbred Lines (RIL) of common carp. It shown that the HLJ319 locus was significantly linked with body size, the same as the result of common carp QTL location.

[Population genetic variation and structure analysis on five populations of mirror carp Cyprinus carpio L. using microsatellites].

In this paper, population genetic variability and genetic structure of five populations of an important cultivation species, mirror carp (Cyprinus carpio L.) were analyzed using 30 microsatellite loci. The observed (Ho) and expected (He) heterozygosity values, polymorphic information content (PIC) and number of effective alleles (Ae) were all determined. The genetic similarity coefficient and Nei's standard genetic distance were computed based on the allele frequencies. The Hardy-Weinberg equilibrium was checked by chi2 test. Genetic differentiation and hierarchical partition of genetic diversity were evaluated by FST and Nm. A dendrogram was constructed based on UPGMA methods using PHYLIP software package supported by a bootstrap value of 91.0%. Totally 7,083 fragments were procured. Their lengths were from 102 bp to 446 bp. For each locus, 1-16 alleles were amplified, adding up to 356 alleles in all the 5 populations. We found the genetic variability level was relatively high in all five populations, as shown by Ae = 1.07-2.30, He= 0.70-0.78 and PIC=0.69-0.75, respectively. The genetic similarity coefficients were all above 0.52, indicating their close genetic relationships. The UPGMA phylogenetic tree showed mirror carps sampled from Donggang, Fengcheng and Liaozhong were clustered into one group and the other two populations, both collected from Songpu, were grouped together. There were obvious relations between genetic distances and geographical distributions of the five populations. No fragments were amplified from some loci of EST-SSRs, which may suggest the loss of these loci in mirror carp genome or sequence divergence at the primer binding sites. These null alleles may result from selection because functional genes are under more selection pressure than non-encoding loci. Overall, population genetic variation is high for each of the five mirror carp, and the differentiations are also significant among populations.