Typical heavy metals accumulation, transport and allocation in a deglaciated forest chronosequence, Qinghai-Tibet Plateau.

Understanding heavy metals (HMs) accumulation and transportation is the foundation to assess the ecological risks caused by the pollution of HMs in terrestrial ecosystems. There are large knowledge gaps regarding impacts of vegetation succession on shaping the HMs accumulation, transportation and allocation in the remote alpine regions. Herein, we comprehensively investigated the distribution and source contribution of mercury (Hg), cadmium (Cd) and chromium (Cr) along with vegetation succession in a deglaciated forest chronosequence of Qinghai-Tibet Plateau. Results showed that Hg and Cd were highly enriched in organic soils, while Cr concentrations and pool sizes decreased significantly with the vegetation succession. Atmospheric Hg deposition contributed to the dominant Hg sources in topsoil (74 - 87%), whereas moraine weathering was the main source of Cr (73 - 76%). Both moraine (18 - 48%) and atmospheric deposition inputs (52 - 82%) affected Cd accumulation in topsoil. Over the last century, the accumulation rate of Hg and Cd showed the distinctly decreasing trends due to the vegetation leading to the elevated atmospheric depositions at the earlier deglacial sites. The negative accumulation rate of Cr along with the vegetation succession reflected the formation of organic soil diluting the geogenic inputs of Cr.

Silicone-Based Thermally Conductive Gel Fabrication via Hybridization of Low-Melting-Point Alloy-Hexagonal Boron Nitride-Graphene Oxide.

Thermal contact resistance between the microprocessor chip and the heat sink has long been a focus of thermal management research in electronics. Thermally conductive gel, as a thermal interface material for efficient heat transfer between high-power components and heat sinks, can effectively reduce heat accumulation in electronic components. To reduce the interface thermal resistance of thermally conductive gel, hexagonal boron nitride and graphene oxide were hybridized with a low-melting-point alloy in the presence of a surface modifier, humic acid, to obtain a hybrid filler. The results showed that at the nanoscale, the low-melting-point alloy was homogeneously composited and encapsulated in hexagonal boron nitride and graphene oxide, which reduced its melting range. When the temperature reached the melting point of the low-melting-point alloy, the hybrid powder exhibited surface wettability. The thermal conductivity of the thermally conductive gel prepared with the hybrid filler increased to 2.18 W/(m·K), while the corresponding thermal contact resistance could be as low as 0.024 °C/W. Furthermore, the thermal interface material maintained its excellent electric insulation performance, which is necessary for electronic device applications.

Latitudinal gradient for mercury accumulation and isotopic evidence for post-depositional processes among three tropical forests in Southwest China.

Tropical forest contributes to > 50% of global litterfall mercury (Hg) inputs and surface soil Hg storage, while with limited understanding of Hg biogeochemical processes. In this study, we displayed the 5-m resolution of Hg spatial distribution in three 1-ha tropical forest plots across the latitudinal gradient in Southwest China, and determined Hg isotopic signatures to understand factors driving Hg spatial distribution and sequestration processes. Our results show that tropical forest at the lowest latitude has the highest litterfall Hg input (74.95 versus 34.14-56.59 µg m-2 yr-1 at higher latitude plots), but the smallest surface soil Hg concentration (2-3 times smaller than at higher latitude sites). Hg isotopic evidence indicates that the decreasing climate mediated microbial Hg reduction in forest floor leads to the increasing Hg accumulation along the latitudinal gradient in three tropical forests. The terrain induced indirect effects by influencing litterfall Hg inputs, soil organic matters distribution and interplays between surface and deep soils drive the heterogeneity of surface soil Hg distribution within each sampling plot. Our results highlight though the elevated litterfall Hg inputs, the distinct post-depositional reductions induced Hg loss would remarkedly decrease atmospheric Hg net sink in tropical forest.

Decline of serum HBV DNA and no change apportioned by the same hepatic parenchyma cell volume from hepatic fibrosis stage 1 to stage 4 during the natural history of chronic hepatitis B.

During the initial phase of chronic hepatitis B virus (HBV) infection, serum HBV DNA levels are high. Contrarily, fibrosis, cirrhosis and hepatocellular carcinoma have been found in patients with lower serum HBV DNA levels. The aim of this study is to clarify HBV DNA level dynamics of serum apportioned by the same hepatic parenchyma cell volume (HPCV) in hepatic fibrosis stages 1-4 during the natural history of chronic hepatitis B. Serum HBV DNA levels were evaluated by real-time polymerase chain reaction. Further, serum HBV DNA levels were apportioned by and compared with the same HPCV in hepatic fibrosis stages 1-4, respectively. Serum HBV DNA levels were 8.91 x 10(6) +/- 4.37 x 10(1), 8.13 x 10(6) +/- 7.41 x 10(1), 9.55 x 10(5) +/- 1.02 x 10(2), and 4.07 x 10(5) +/- 7.24 x 10(1) copies/ml, respectively; there were differences among hepatic fibrosis stages 1-4 (p < 0.021-0.000). However, serum HBV DNA levels apportioned by the same volume of hepatic parenchyma cells in hepatic fibrosis stages 1-4 were 3.47 x 10(10) +/- 8.71 x 10(2), 1.02 x 10(11) +/- 9.55 x 10(2), 1.41 x 10(10) +/- 2.57 x 10(3), and 3.72 x 10(10) +/- 3.02 x 10(3) with HPCV proportions 65.9, 62.7, 58.9, and 53.3%, respectively; there were no differences among hepatic fibrosis stages 1-4 (p > 0.203-0.967).Following the progression of hepatic fibrosis from stage 1 to 4, ongoing decline of HPCV is responsible for a declining trend of serum HBV DNA levels.

Etiological investigation of fatal liver failure during the course of chronic hepatitis B in southeast China.

BACKGROUND: The purpose of this study was to clarify the relationships between patients who had fatal liver failure during the course of chronic hepatitis B and those who were also superinfected with hepatitis A, C, D, or E virus, as well as their hepatitis B virus e system status, so that suitable measures could be adopted to decrease the mortality of patients with chronic hepatitis B. METHODS: This study detected superinfections of hepatitis A, C, D, or E virus and the hepatitis B virus e system status in cases of fatal liver failure during the course of chronic hepatitis B by enzyme-lined immunosorbent assay. RESULTS: The frequency of superinfections of hepatitis A, C, D, and E virus was 1.4% (4/282), 6.4% (18/282), 1.8% (5/282), and 28.4% (80/282), respectively, overall, 37.9% (107/282). Hepatitis E was prominent and steady in superinfection rates during the past 12 years. In 62.1% (175/282) of patients, the causes of fatal liver failure were not clear. The serological status frequency of HBeAg(+) and anti-HBe(-), HBeAg(-) and anti-HBe(-), and HBeAg(-) and anti-HBe(+) was 20.6% (22/107), 23.4% (25/107), and 56.1% (60/107), respectively, in the group with superinfections of hepatitis A, C, D, or E virus and 31.4% (55/175), 21.1% (37/175), and 47.4% (83/175), respectively, in the group in which causes were not clear. The serological status HBeAg(+) and anti-HBe(-) was more frequent in the group in which causes were not clear than in the group with superinfections of hepatitis A, C, D, or E virus (P < 0.05). Statistically, there were no differences (P > 0.05) between the serological status HBeAg(-), anti-HBe(-) and HBeAg(-), anti-HBe(+) between the two groups. CONCLUSIONS: These results suggest that superinfection (107/282) is an important factor in fatal liver failure. The mortality of chronic hepatitis B can be decreased by strict food sanitation and the use of safe blood products. There were no significant relationships between hepatitis B e antigen seroconversion and fatal liver failure during the course of chronic hepatitis B.

[Detection of fetal SRY gene in maternal plasma by real-time fluorescence quantitative PCR].

OBJECTIVE: To isolate fetal DNA from maternal plasma and examine its fetal origin. METHODS: Fetal DNA in maternal plasma was isolated from 150 samples in the first trimester and mid-trimester of pregnancy, respectively. Real-time fluorescence quantitative polymerase chain reaction PCR (FQ-PCR) was used to determine sex-determining region Y (SRY) gene on Y chromosome. RESULTS: Eighty-two women in the first trimester and 90 women in the mid-trimester carried male fetuses,70 and 90 samples of them were positive, respectively. The mean concentrations were (58.82+/-20.90) copies/ml and (152.08+/-62.61) copies/ml. The results of FQ-PCR were negative in the women who carried female fetuses. CONCLUSION: The results show that fetal SRY gene can be found at a time as early as 42 days of gestation in maternal plasma by the use of FQ-PCR. The number of fetal DNA increases with gestational age. The real-time FQ-PCR is of great value in the non-invasive prenatal diagnosis.