Comparative analysis of the essential oils from normal and hairy roots of Panax japonicas C.A. Meyer

The essential oils were extracted with steam distillation from normal and hairy roots of Panax japonicus C.A. Meyer. The constituents of essential oils were analyzed by gas chromatography mass spectrometry (GC-MS). The results showed that 40 and 46 kinds of compounds were identified from the essential oils of normal and hairy roots; they amount to 93.3 and 95.89% of the total detected constituents, respectively. Both of them own 18 kinds of same compounds, relative peak areas all exceed 50%, except that, the roots alone own 22 kinds of compounds, and the hairy roots alone own 28 kinds of compounds. In the roots, those higher content compounds were hexanoic acid (11.6%), falcarinol (10.04%) and 3-methylbutyric acid (9.56%); however, in the hairy roots, they were caproic acid (13.92%), spathulenol (9.96%), 1H-cycloprop azulene (9.15%). These compounds have lots of bioactivity, for anticancer, antitumor and antibiosis among others. The result showed tremendous value on producing the medical components with the skill of hairy roots.Key words: Panax japonicus, essential oils, gas chromatography mass  spectrometry

Rock-salt SnS and SnSe: Native Topological Crystalline Insulators

Unlike time-reversal topological insulators, surface metallic states with Dirac cone dispersion in the recently discovered topological crystalline insulators (TCIs) are protected by crystal symmetry. To date, TCI behaviors have been observed in SnTe and the related alloys Pb$_{1-x}$Sn$_{x}$Se/Te, which incorporate heavy elements with large spin-orbit coupling (SOC). Here, by combining first-principles and {\it ab initio} tight-binding calculations, we report the formation of a TCI in the relatively lighter rock-salt SnS and SnSe. This TCI is characterized by an even number of Dirac cones at the high-symmetry (001), (110) and (111) surfaces, which are protected by the reflection symmetry with respect to the ($\bar{1}$10) mirror plane. We find that both SnS and SnSe have an intrinsically inverted band structure and the SOC is necessary only to open the bulk band gap. The bulk band gap evolution upon volume expansion reveals a topological transition from an ambient pressure TCI to a topologically trivial insulator. Our results indicate that the SOC alone is not sufficient to drive the topological transition.Comment: 5 pages, 5 figure

Tuning the vertical location of helical surface states in topological insulator heterostructures via dual-proximity effects

In integrating topological insulators (TIs) with conventional materials, one crucial issue is how the topological surface states (TSS) will behave in such heterostructures. We use first-principles approaches to establish accurate tunability of the vertical location of the TSS via intriguing dual-proximity effects. By depositing a conventional insulator (CI) overlayer onto a TI substrate (Bi2Se3 or Bi2Te3), we demonstrate that, the TSS can float to the top of the CI film, or stay put at the CI/TI interface, or be pushed down deeper into the otherwise structurally homogeneous TI substrate. These contrasting behaviors imply a rich variety of possible quantum phase transitions in the hybrid systems, dictated by key material-specific properties of the CI. These discoveries lay the foundation for accurate manipulation of the real space properties of TSS in TI heterostructures of diverse technological significance

Drought Occurring With Hot Extremes: Changes Under Future Climate Change on Loess Plateau, China

© 2019. The Authors. Drought is one of the most widespread and destructive hazards over the Loess Plateau (LP) of China. Due to climate change, extremely high temperature accompanied with drought (expressed as hot drought) may lead to intensive losses of both properties and human deaths in future. A hot drought probabilistic recognition system is developed to investigate how potential future climate changes will impact the simultaneous occurrence of drought and hot extremes (hot days exceeding certain values) on the LP. Two regional climate models, coupled with multiple bias-correction techniques and multivariate probabilistic inference, are innovative integrated into the hot drought probabilistic recognition system to reveal the concurrence risk of droughts and hot extremes under different Representative Concentration Pathway (RCP) scenarios. The hot-day index, TX90p, indicating the number of days with daily maximum temperature (Tmax) exceeding the 90th percentile threshold, and the Standardized Precipitation Index are applied to identify the joint risks on the LP using copula-based methods. The results show that precipitation will increase throughout most of the LP under both RCP4.5 and RCP8.5 scenarios of 2036–2095, while Tmax may increase significantly all over the LP (1.8–2.7 °C for RCP4.5 and 2.7–3.6 °C for RCP8.5). The joint return periods of Standardized Precipitation Index and TX90p show that fewer stations will experience severe drought with long-term hot extremes in two future scenarios. However, some stations may experience hot droughts that are more frequent and extreme, particularly certain stations in the southwest and south-central regions of the LP with recurrence period less than 10 years.This research was supported by the National Key Research and Development Plan (2016YFA0601502), the Natural Sciences Foundation (51520105013, 51679087), the 111 Program (B14008), the Natural Science and Engineering Research Council of Canada, and the Fundamental Research Funds for the Central Universities (2016XS89). The observed temperature and precipitation data are collected and available at the National Meteorological Information Center (http://data.cma.cn/). The RCM simulations are available at Climate Change Data Portal (http://chinaccdp.org/)

Development of specific PCR assays for the detection of Cryptocaryon irritans

Cryptocaryon irritans is one of the most important protozoan pathogens of marine fish, causing the “white spot” disease and posing a significant problem to marine aquaculture. In the present study, a C. irritans-specific reverse primer (S15) was designed based on the published sequence of the second internal transcribed spacer (ITS-2) of ribosomal DNA (rDNA) of C. irritans and used together with the conserved forward primer P1 to develop a specific polymerase chain reaction (PCR) assay for direct, rapid, and specific detection of C. irritans. The specificity of these primers was tested with both closely and distantly related ciliates (Pseudokeroronpsis rubra, Pseudokeroronpsis carnae, Euplotes sp. 1, Ichthyophthirius multifiliis, Pseudourostyla cristata, and Paramecium caudaium), and only C. irritans was detected and no product was amplified from any other ciliates examined in this study using the specific primer set P1-S15. The specific PCR assay was able to detect as low as 45 pg of C. irritans DNA and a nested PCR assay using two primer sets (P1/NC2, P1/S15) increased the sensitivity, allowing the detection of a single C. irritans. The species-specific PCR assays should provide useful tools for the diagnosis, prevention, and molecular epidemiological investigations of C. irritans infection in marine fish

Effect of laser remelting on microstructure and properties of WC reinforced Fe-based amorphous composite coatings by laser cladding

The WC reinforced Fe-based amorphous composite coatings were prepared by laser cladding with rectangular spot. The effect of laser remelting on the microstructure and properties of composite coatings was investigated. The results showed that laser remelting can reduce the cracks and porosities of the cladding coating and improve its surface quality. Large amounts of crystalline phases were precipitated at the top of the cladding and remelting coatings. However, the microstructure at the top of the remelting coating was finer compared to that at the top of the cladding coating. With increasing distance from the surface of substrate, the amorphous phase appeared within the remelting coating and large amounts of carbides rich in Fe and Mo, Fe23B6, gamma-Fe and Cr-9.1.Si-0.9 Slag phases were also precipitated in the remelting coating. As a result, the corrosion resistance of the remelting coating was higher than that of the cladding coating. The microhardness of the remelting coating was approximately 1.13 times higher than that of the cladding coating. (C) 2018 Elsevier Ltd. All rights reserved

The prevalence of metabolic syndrome and cardiovascular risk factors in adults in southern China

<p>Abstract</p> <p>Background</p> <p>The metabolic syndrome has been shown to increase the incidence of cardiovascular disease. Little information exists on the prevalence of the metabolic syndrome for southern Chinese. We therefore investigate the prevalence of the metabolic syndrome in a southern Chinese population with 85 million residents.</p> <p>Methods</p> <p>The Guangdong Nutrition and Health Survey 2002 is a cross-sectional survey designed to assess the health and nutritional status of 85 million residents in Guangdong province located in southern China. Stratified multistage random sampling method was applied in this survey and a provincial representative sample of 6,468 residents aged 20 years or above was obtained in the present study. The participants received a full medical check-up including measurement of blood pressure, obesity indices, fasting lipids and glucose levels. Data describing socioeconomic and lifestyle factors was also collected through interview. Metabolic syndrome was defined in accordance with the International Diabetes Federation criteria.</p> <p>Results</p> <p>The prevalence of metabolic syndrome was 7.30%, translating into a total of 4.0 million residents aged 20 years or above having the condition in this southern Chinese population. The urban population had higher prevalence of the syndrome than the rural population (10.57% vs 4.30%). Females had a higher prevalence of metabolic syndrome than males (8.99% vs 5.27%). More than 60% of the adults had at least one component of the metabolic syndrome.</p> <p>Conclusions</p> <p>Our results indicate that a large proportion of southern Chinese adults have the metabolic syndrome and associated risk factors. The metabolic syndrome has become an important public health problem in China. These findings emphasize the urgent need to develop population level strategies for the prevention, detection, and treatment of cardiovascular risk in China.</p