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An organocatalytic asymmetric Mannich reaction of pyrazoleamides with cyclic trifluoromethyl ketimines: enantioselective access to dihydroquinazolinone skeletons
No full textAn organocatalyzed asymmetric Mannich reaction of pyrazole-amides and cyclic trifluoromethyl ketimines with a chiral bifunctional amine-squaramide as the catalyst was developed. A wide range of trifluoromethyl dihydroquinazolinone derivatives bearing adjacent quaternary and tertiary stereogenic centers were readily obtained in good to excellent yields (up to 99%) with high diastereo- and enantioselectivities (up to 99% ee and >20 : 1 dr). The large scale experiment and transformation of the product have also been demonstrated
Osteology of Batrachuperus londongensis (Urodela, Hynobiidae): study of bony anatomy of a facultatively neotenic salamander from Mount Emei, Sichuan Province, China
No full textThe Longdong Stream Salamander Batrachuperus londongensis, living in a mountain stream environment at Mt. Emei in Sichuan Province, China, represents a rare species that is facultatively neotenic in the family Hynobiidae. Although the species has been known to science for some 40 years since its initial discovery in the late 1970s, anatomical details of its osteology remain poorly understood and developmental information is still lacking for the species. This study (1) provides a detailed osteological account of B. londongensis based on micro-CT scanning and clearing and staining of multiple specimens from the type locality; (2) provides a discussion of intraspecific variation related to life-history differences; and (3) presents a discussion on limb features related to morphological evolution of limb patterns correlative with ecological adaptation to mountain stream environments. Osteological comparisons with congeneric species has led to recognition of several diagnostic features that are unique to B. londongensis, including: vomers widely separated from one another, lacking a midline contact; presence of uncommon perichondral ossification of the ascending process of the palatoquadrate as part of the suspensorium; and presence of a prominent posterodorsal process of the scapular blade, which serves as a ligamentous insertion of the levator muscle of the scapula. In addition, some but not all neotenic individuals retain the palatine as a discrete element, indicative of its delayed absorption after sexual maturity. Postmetamorphic and neotenic individuals are strikingly different in the complexity of hyobranchial structures. Neotenes display a high degree of ossification of hyobranchial elements, tend to increase ossification of both hypobranchial I and ceratobranchial I during aging, and retain fully ossified ceratobranchial III and IV; in contrast, these elements remain entirely cartilaginous or are totally lost by resorption in postmetamorphic individuals. In addition, all postmetamorphic forms display an inverted "T"-shaped basibranchial II, whereas neotenes show transformation from a "fork"-shaped to the "T"-shaped configuration after sexual maturity. B. londongensis displays a mosaic of apomorphic and plesiomorphic states in its limb ossifications: presence of a single centrale element in both the manus and pes is a derived condition in Hynobiidae and other families as well, whereas retention of a postminimus in the pes is obviously plesiomorphic within Urodela. Reduction in number of digits from five to four in the pes and possession of a cornified sheath covering the terminal phalanges are also derived features shared with some but not all mountain stream salamanders that are adapted to a similar type of environment
Diastereo- and Enantioselective Dearomative [3+2] Cycloaddition Reaction of 2-Nitrobenzofurans with 3-Isothiocyanato Oxindoles
No full textEnantioselective dearomative [3 + 2] cycloaddition reaction of 2-nitrobenzofurans with 3-isothiocyanato oxindoles was developed. The reaction employs a chiral bis(oxazoline)/Zn(OTf)(2) catalyst, allowing a practical, straightforward access to structurally diverse spirooxindoles containing a 2,3-dihydrobenzofuran motif and three contiguous stereo-centers with excellent diastereo- and enantioselectivities. The synthetic potentials of the method have been demonstrated by the scale-up experiment and transformations of the products. The preliminary mechanism was investigated with experimental observations, nonlinear effects studies, and MS experiments
Impacts of wise grazing on physicochemical and biological features of soil in a sandy grassland on the Tibetan Plateau
No full textDesertification is a serious environmental problem on the Tibetan Plateau and various strategies, such as long-term fencing and grazing management, have been implemented in that region to control the soil degradation. However, little is known about the role of interactions among the soil aggregate, microbial communities, and nutrient traits in the soil restoration. In this study, we compared the effects of different restoration strategies on the formation of aggregates, the amount and distribution of soil nutrients, as well as the abundance and diversity of bacteria in a sandy soil of grassland at the Tibetan Plateau. The results demonstrated that both the grazing exclusion (GE: artificial planting and nutrient addition) and wise grazing (WG: artificial planting and nutrient addition with controlled grazing) treatments significantly increased the proportion of macroaggregates (4.0-and 5.2- times, p < 0.05) compared with the control. Increased soil organic carbon, total carbon, total nitrogen, and total phosphorus were found in the aggregates of WG treatment, but not in the GE samples. In addition, WG significantly changed the bacterial composition and increased bacterial abundance in soil. This study evaluated WG as an efficient management for restoration of degraded sandy grassland in the Tibetan Plateau because it significantly enriched the soil nutrients, improved the soil structure, and increased bacterial abundance. This is the first study to relate the aggregates with nutrient accumulation and bacterial community during the soil restoration in the Tibetan Plateau
Structural and functional differentiation of the microbial community in the surface and subsurface peat of two minerotrophic fens in China
No full textBackground and aimsMicrobial communities are the primary drivers of organic matter decomposition in peatlands. However, limited knowledge is available regarding depth-dependent microbial community structure and function in East Asian peatlands, using cultivation independent approaches.MethodsWe investigated the vertical stratification of prokaryote and fungal communities in a moderately rich fen in northeast China (Hani) and a rich fen in southwest China (Riganqiao).ResultsFungal and prokaryotic operational taxonomic unit (OTU) composition exhibited strong site and/or depth responses. Prokaryotic OTUs exhibited the greatest alpha diversity at the mesotelm hot spot', whereas the predicted metagenomic metabolic functions did not align with the pattern of prokaryote alpha diversity. The large cover of shrubs contributed to a greater relative abundance of ericoid- and ecto-mycorrhizal fungi at Hani, whereas Riganqiao showed more arbuscular mycorrhizal fungi. Soil pH and water table depth were among the predominant abiotic factors associated with microbial community composition.ConclusionsProjected shifts in hydrology and/or vegetation with global change may cause substantial impacts on peatland microorganisms and thus the associated biogeochemistry. It is critical to better understand the mechanism of the discrepancy between microbial community structure and the functions at the mesotelm hot spot' when evaluating the ecosystem functions in peatlands
Climate and soil parameters are more important than denitrifier abundances in controlling potential denitrification rates in Chinese grassland soils
No full textDenitrification is an important process that influences nitrogen (N) loss and the production of greenhouse gas in grassland soils. However, the relative contributions of abiotic and biotic factors to soil denitrification potential at the regional and sub-regional scales in grassland ecosystems remain elusive. In this study, soil samples were collected from 21 sites at three steppes of China, including the Inner Mongolia Plateau (IMP), the Xinjiang Autonomous Region (XAR) and the Tibetan Plateau (TP) grasslands. Results showed that the key factors controlling the denitrification potential were regional and scale-dependent. At the sub-regional scales, soil pH, aridity index (AI) and total organic carbon (TOC) explained the highest variances on denitrification potential in the IMP, XAR and TP steppe, respectively. At the regional scale, the mean annual precipitation (MAP) was the most important environmental driver for the denitrification potential. Partial least squares (PLS) path modeling revealed that the MAP might regulate denitrification potential directly and indirectly by its effects on the plant and soil properties. Overall, these results help to improve our understandings on the prediction of the denitrification potential under global changes and revealed that the denitrification potential at various scales could be regulated by the multiple interactions of abiotic and biotic factors. (C) 2019 Published by Elsevier B.V
Rapid analysis of sludge concentration using a microwave-assisted heating method: Parameters, modelling, and application
No full textIn this paper, the parameters, models, and application of a microwave-assisted heating (MWAH) method for rapid analysis of sludge concentration were studied. For activated/physicochemical sludge concentrations (2000-4000 mg/L) analysis, the feasible parameters using a MWAH method were microwave drying time of 5-10 min with microwave radiation power of 280, 560, 800 W, respectively. F- and t-tests confirmed that there were no significant differences between MWAH and conventional method. MWAH models between activated/physicochemical sludge concentrations (1000-12,000 mg/L), microwave radiation power as well as drying time were established. The relative errors were in the range of +/- 10% by applying these models. In addition, MWAH model based on 800 W of microwave radiation power was applied for rapid analysis of real wastewater sludge samples with different properties. Results demonstrated that sludge concentrations determined by MWAH method had high precision and could satisfy the analysis requirement of conventional method. Compared with conventional method, the microwave drying time and energy consumption by MWAH method can be reduced by 83.3% and 86.7%, respectively. Our study indicated that MWAH method was a rapid and low energy alternative to conventional method for sludge concentration determination in wastewater treatment systems
Female-biased Dispersal of the Emei Moustache Toad (Leptobrachium boringii) under Local Resource Competition
Full text linkDispersal is an important area of ecological and evolutionary research. Although many studies have been conducted in mammals and birds, dispersal pattern in amphibians is still unclear. To verify dispersal patterns of amphibians, an endangered species the Emei Moustache Toad (Leptobrachium boringii) was selected. In this study, we analyzed six genetic parameters: inbreeding coefficient (FIS), gene diversity (HS), the mean of corrected assignment index (mAIC), the variance of corrected assignment index (vAIC), relatedness (r) for all three years together and each year separately based on eight highly polymorphic microsatellite loci. Data in totaled across years and each year for 581 individuals captured during 2013–2015 revealed a significant female-biased dispersal pattern. Significantly higher FIS and HS in females, and lower mAIC and r for each year separately in females support that L.boringii displays female-biased dispersal, although r for the total dataset and vAIC tests did not show significant differences between the sexes. Female-biased dispersal patterns may be explained by the local resource competition hypothesis
Macroecological Patterns of Climatic Niche Breadth Variation in Lacertid Lizards
Full text linkMeasuring climatic niche position and breadth may help to determine where species can occur over space and time. Using GIS-based and phylogenetic comparative methods, we investigated global patterns of variation in climatic niche breadth in lacertid lizards to test the following three hypotheses about climatic niche widths. First, does a species’ temperature or precipitation niche breadth relate to its temperature or precipitation niche position (the mean value of annual mean temperature or annual precipitation across sampled localities in the range of each species)? Second, are there trade-offs between a species’ temperature niche breadth and precipitation niche breadth? Third, does a species’ temperature or precipitation niche breadth relate to altitude or latitude? We expect that: (1) species distributed in cold regions are specialized for low-temperature environments (i.e. narrow niche breadth center around low temperatures); (2) a negative relationship between species niche breadth on temperature and precipitation axes according to the trade-off hypothesis (i.e. species that tolerate a broad range of precipitation regimes cannot also tolerate a broad range of temperatures); (3) precipitation niche breadth decreases with altitude or latitude, whereas temperature climatic niche breadth increases with altitude or latitude. Based on the analytical results we found that: (1) temperature niche breadth and position are negatively related, while precipitation niche breadth and position are positively related; (2) there is no trade-off between temperature and precipitation niche breadths; and (3) temperature niche breadth and latitude/altitude are positively related, but precipitation niche breadth and latitude/altitude are not significantly related. Our results show many similarities with previous studies on climatic niche widths reported for amphibians and lizards, which provide further evidence that such macroecological patterns of variation in climatic niche breadths may be widespread
Protection of Danio rerio from cadmium (Cd2+) toxicity using biological iron sulfide composites
No full textCadmium (Cd2+) pollution has become a global environmental problem. This study is the first to demonstrate the feasibility and effects of applying biological iron sulfide composites (BISC) for the protection of Cd2+ exposed fish, aiming at remediation of Cd2+ polluted waters during emergency pollution events. Experimental results indicate that BISC can remove Cd2+ efficiently and significantly protect Cd2+ exposed Danio rerio, by increasing its overall survival rates. Meanwhile, the protective effect of BISC is significantly enhanced with optimized BISC dosing ratios of 2.4 or more, as well as with more rapid onset of BISC dosing following Cd2+ exposure and in water with higher pH levels in the range of 6-8, with D. rerio survival rates increased by more than 90% (P = 0.05). Additionally, BISC confers advantages over SRB and combinations of its constituents, with effective removal of Cd2+ and increasing survival rates of Cd2+ exposed D. rerio