Missingness in mixed-type variables is commonly encountered in a variety of areas. The requirement of complete observations necessities data imputation when a moderate or large proportion of data is ***, inappropriate...
Missingness in mixed-type variables is commonly encountered in a variety of areas. The requirement of complete observations necessities data imputation when a moderate or large proportion of data is ***, inappropriate imputation would downgrade the performance of machine learning algorithms, leading to bad predictions and unreliable statistical inference. For high-dimensional large-scale mixed-type missing data, we develop a computationally efficient imputation method, missing value imputation via generalized factor models（MIG）, under missing at random. The proposed MIG method allows missing variables to be of different types,including continuous, binary, and count variables, and are scalable to both data size n and variable dimension p while existing imputation methods rely on restrictive assumptions such as the same type of missing variables,the low dimensionality of variables, and a limited sample size. We explicitly show that the imputation error of the proposed MIG method diminishes to zero with the rate Op(max{n-1/2, p-1/2}) as both n and p tend to infinity. Five real datasets demonstrate the superior empirical performance of the proposed MIG method over existing methods that the average normalized absolute imputation error is reduced by 5.3%–34.1%.
Nitrification is a key step in the global nitrogen *** with autotrophic nitrification,heterotrophic nitrification remains poorly *** this study,Halomonas venusta MA-ZP17-13,isolated from seawater in shrimp aquaculture...
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Nitrification is a key step in the global nitrogen *** with autotrophic nitrification,heterotrophic nitrification remains poorly *** this study,Halomonas venusta MA-ZP17-13,isolated from seawater in shrimp aquaculture (Penaeus vannamei),could simultaneously undertake nitrification and *** the initial ammonium concentration at 100 mg/L,the maximum ammonium-nitrogen removal rate reached98.7%under the optimal conditions including C/N concentration ratio at 5.95,p H at 8.93,and Na Cl at 2.33%.The corresponding average removal rate was 1.37 mg/(L·h)(according to nitrogen) in 3 d at 11.2℃.By whole genome sequencing and analysis,nitrification-and denitrification-related genes were identified,including ammonia monooxygenase,nitrate reductase,nitrite reductase,nitric oxide dioxygenase and nitric oxide synthase;while no gene encoding hydroxylamine oxidase was identified,it implied the existence of a novel nitrification pathway from hydroxylamine to *** results indicate heterotrophic bacterium *** MA-ZP17-13 can undertake simultaneous nitrification and denitrification at low temperature and has potential for NH_(4)^(+)-N/NH_(3)-N removal in marine aquaculture systems.
The method extracting the electromagnetic parameters from scattering coefficients was studied in this paper. The Support Vector Machine (SVM) method is used to solve the inverse problem of parameters extraction. The m...
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The method extracting the electromagnetic parameters from scattering coefficients was studied in this paper. The Support Vector Machine (SVM) method is used to solve the inverse problem of parameters extraction. The mapping relationship is set up by calculating a large number of S pa-rameters from the samples with different permittivity by using transmission line theory. The simulated data set is used as training data set for SVM. After the training, the SVM is used to predict the permittivity of material from the scattering coefficients.
A survey was made of the spore community of arbuscular mycorrhizal fungi (AMF) and root colonization by AMF in 16 plant species in Lhalu wetland on the outskirts of Lhasa city in Tibet. It was found that 13 of the 16 ...
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A survey was made of the spore community of arbuscular mycorrhizal fungi (AMF) and root colonization by AMF in 16 plant species in Lhalu wetland on the outskirts of Lhasa city in Tibet. It was found that 13 of the 16 plant species investigated (81. 5% ) formed arbuscular mycorrhizal structures and dark septate endophytic fungi colonized the roots of most species. Total AMF colonization ranged from 0 to 82. 6% in dicots and 0 to 54. 5% in monocots. Both total AMF and arbuscular colonization were greater in dicots than that in monocots. A total of 48 taxa representing 7 genera of AMF were isolated and identified. Of these,9 species belonged to Acaulospora,2 to Appendicispora,34 to Glomus,and 1 each to Pacispora,Paraglomus and Scutellospora. Spores of Glomus aggregatum,G. deserticola and G. etunicatum were most common and abundant in the spore survey. Spores of 8 to 26 AMF species were isolated from the rhizosphere soil of individual plant species. Spore densities in soil associated with the 16 plant species ranged from 20 to 475 per 20 g soil,with an average of (92. 3 ± 14. 6). Species richness of AMF ranged from 6 to 12. 7. There were no significant differences between dicots and monocots in AMF spore density or species richness. Future work directed towards under- standing the response of the wetland plants to AMF may provide some insight into the role that these fungal symbionts may play in influencing plant diversity in this important urban wetland.
DNA methylation is known to play a crucial role in regulating plant development and or- gan or tissue differentiation. In this study, we as- sessed the extent and pattern of cytosine methylation during rapeseed (Brass...
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DNA methylation is known to play a crucial role in regulating plant development and or- gan or tissue differentiation. In this study, we as- sessed the extent and pattern of cytosine methylation during rapeseed (Brassica napus L.) seed germina- tion, and compared the methylation level of various tissues in seedling, using the techniques of methyla- tion-sensitive amplified polymorphism (MSAP) and HPLC separation and quantification of nucleosides. In all, 484 bands, each representing a recognition site cleaved by either or both of the isoschizomers, were amplified by 12 pairs of selective primers in DNA ob- tained from dry seeds. A total of 76 sites were found to be differentially digested by the isoschizomers, indicating that approximately 15.7% of 5′-CCGG-3′ sites in the genome were cytosine methylated. Four classes of patterns were observed in a comparative assay of cytosine methylation in the dry and germi- nating seeds; a small number of hypermethylation events occurred at 5′-CCGG-3′ sites in germinating seeds compared with dry seeds, while many more hypomethylation events were detected after seed germination. Differences in DNA methylation level in various tissues were also detected; radicel was less methylated than hypocotyl and cotyledon. These observations were further confirmed by HPLC analy- sis. In addition, sequencing of eleven differentially methylated fragments and the subsequent blast search revealed that cytosine methylated 5′-CCGG- 3′ sequences were equally distributed between cod- ing and non-coding regions. These results clearly demonstrate the power of MSAP technique for large-scale DNA methylation detection in rapeseed genome, and the complexity of DNA methylationchange during seed germination. DNA Hypomethyla- tion going with seed germination appears to be a necessary step toward transcriptional activation in gene expression, and may well contribute to the de- velopmental gene regulation.
The techniques of oxygen electrode polarogra-phy and Fourier transform infrared (FT-IR) spectroscopy were employed to explore the roles of polar head-group of phosphatidylglycerol (PG) molecules in the functional and ...
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The techniques of oxygen electrode polarogra-phy and Fourier transform infrared (FT-IR) spectroscopy were employed to explore the roles of polar head-group of phosphatidylglycerol (PG) molecules in the functional and structural aspects of photosystem Ⅱ (PS Ⅱ) through enzymatic approach. It was shown that the depletion of PG by treatment of phospholipase C (PLC) on PS Ⅱ particles caused the inhibition of oxygen evolving activity in PS Ⅱ. This effect also gave rise to changes in the protein secondary structures of PS Ⅱ, that is, an increase in a-helical conformation which is compensated by the loss of p-strand structures. It revealed that the head-group of PG molecules plays an important structural role in the maintenance of normal structure of PS Ⅱ proteins, which is required to maintain the appropriate physiological activity of the PS Ⅱ complex such as the oxygen evolving activity. It is suggested that there most probably exist hydrogen-bonding interactions between PG molecules and PS Ⅱ proteins.
Twelve kinds of alcohol-based deep eutectic solvents（DESs） using choline chloride（ChCl） with different hydrogen donors（glycerol, glycol, and 1, 2-propanediol） with mixing ratios（1:2, 1:3, 1:4, 1:5, n/n） were p...
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Twelve kinds of alcohol-based deep eutectic solvents（DESs） using choline chloride（ChCl） with different hydrogen donors（glycerol, glycol, and 1, 2-propanediol） with mixing ratios（1:2, 1:3, 1:4, 1:5, n/n） were prepared under the reaction temperature of 80°C. Fourier transform infrared spectrometer（FT-IR） was used to analyze the spectra of the twelve kinds of alcohol-based DESs. Then alcohol-based DESs were used as the additives of mobile phase with the volume percent of additive（0.10%, v/v） to optimize chromatographic analysis of ferulic acid（FA） in high performance liquid chromatography（HPLC）. The result showed that alcohol-based DESs as additives shorten the retention time and modified the chromatogram shape, proving alcohol-based DESs as additives for effective theoretical plate numbers and tailing factors in HPLC. DES-7 with ChCl and glycol（1:4, n/n） was observed as the best additive among the alcohol-based DESs, and the mean chromatographic theoretical plate numbers and tailing factors of the FA under this condition were 3254.22 and 1.08.
＜正＞Molecularly impr inted polymers（MIPs）with caffeic acid as template and non-imprinted polymers（NIPs）materials were prepared in an in an identical *** emission scanning electron microscopy（FE-SEM）and adsorpt...
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＜正＞Molecularly impr inted polymers（MIPs）with caffeic acid as template and non-imprinted polymers（NIPs）materials were prepared in an in an identical *** emission scanning electron microscopy（FE-SEM）and adsorption capacity test were used to evaluate characteristics of the new
A taxonomic study was carried out on strain GCS-AE-31 T, which was isolated from a phenol-degrading consortium, enriched from coking wastewater activated sludge of Beijing Shougang Company limited during the screening...
A taxonomic study was carried out on strain GCS-AE-31 T, which was isolated from a phenol-degrading consortium, enriched from coking wastewater activated sludge of Beijing Shougang Company limited during the screening of phenol-degrading bacteria. Cells of strain GCS-AE-31 T were Gram-negative, short rods, gliding motile, oxidase-/catalase-positive. Growth was observed at salinities from 0 to 3 % and at temperatures from 10 to 37 °C. On the basis of 16 S rR NA gene sequence similarity, strain GCS-AE-31 T was most closely to Pedobacter saltans LMG 10337T(96.17 %), but it showed low similarity to all other species of genus Pedobacter(89.28-92.45 %). It also showed low 16 S rR NA similarity to all other species of the family Sphingobacteriaceae(87.25-92.45 %). The dominant fatty acids were iso-C15:0(34.5 %), Sum In Feature 3(C16:1ω7c/C16:1ω6c, 18.6 %), anteiso-C15:0(7.1 %) and iso-C17:0 3-OH(6.4 %). The menaquinones were MK-7(95.5 %) and MK-6(4.5 %). The polar lipids were phosphatidylethanolamine, three aminolipids and three unknown phospholipids. Sphingolipid was present. The G+C content of the chromosomal DNA was 36.2 mol%. According to its phylogenetic position and phenotypic traits, the novel strain could not be assigned to the genus Pedobacter, it should be classified as a novel species of a new genus in the family Sphingobacteriaceae, for which the name Pseudopedobacter beijingensis gen. nov., sp. nov. is proposed(type strain GCS-AE-31 T =MCCC 1A01299 T = CGMCC NO 1.12329 T = LMG 27180T). The misclassified species Pedobacter saltans is transferred to the new genus as Pseudopedobacter saltans com. nov.(type strain LMG 10337 T = MCCC 1A06472 T = DSM 12145 T = CCUG 39354 T = CIP 105500 T = JCM 21818 T = NBRC 100064T).
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