X.D. Zhang

First results of the use of a continuously flowing lithium limiter in high performance discharges in the EAST device

As an alternative choice of solid plasma facing components (PFCs), flowing liquid lithium can serve as a limiter or divertor PFC and offers a self-healing surface with acceptable heat removal and good impurity control. Such a system could improve plasma performance, and therefore be attractive for future fusion devices. Recently, a continuously flowing liquid lithium (FLiLi) limiter has been successfully designed and tested in the EAST superconducting tokamak. A circulating lithium layer with a thickness of <0.1 mm and a flow rate ~2 cm3 s−1 was achieved. A novel in-vessel electro-magnetic pump, working with the toroidal magnetic field of the EAST device, was reliable to control the lithium flow speed. The flowing liquid limiter was found to be fully compatible with various plasma scenarios, including high confinement mode plasmas heated by lower hybrid waves or by neutral beam injection. It was also found that the controllable lithium emission from the limiter was beneficial for the reduction of recycling and impurities, for the reduction of divertor heat flux, and in certain cases, for the improvement of plasma stored energy, which bodes well application for the use of flowing liquid lithium PFCs in future fusion devices.

Reconstitution of UCP1 using CRISPR/Cas9 in the white adipose tissue of pigs decreases fat deposition and improves thermogenic capacity

Significance Uncoupling protein 1 (UCP1) is responsible for brown adipose tissue-mediated thermogenesis and plays a critical role in protecting against cold and regulating energy homeostasis. Modern pigs lack functional UCP1, which makes them susceptible to cold and prone to fat deposition and results in neonatal mortality and decreased production efficiency. In the current study, a CRISPR/Cas9-mediated homologous recombination-independent approach was established, and mouse adiponectin-UCP1 was efficiently inserted into the porcine endogenous UCP1 locus. The resultant UCP1 KI pigs showed an improved ability to maintain body temperature, decreased fat deposition, and increased carcass lean percentage. UCP1 KI pigs are a potentially valuable resource for the pig industry that can improve pig welfare and reduce economic losses. Uncoupling protein 1 (UCP1) is localized on the inner mitochondrial membrane and generates heat by uncoupling ATP synthesis from proton transit across the inner membrane. UCP1 is a key element of nonshivering thermogenesis and is most likely important in the regulation of body adiposity. Pigs (Artiodactyl family Suidae) lack a functional UCP1 gene, resulting in poor thermoregulation and susceptibility to cold, which is an economic and pig welfare issue owing to neonatal mortality. Pigs also have a tendency toward fat accumulation, which may be linked to their lack of UCP1, and thus influences the efficiency of pig production. Here, we report application of a CRISPR/Cas9-mediated, homologous recombination (HR)-independent approach to efficiently insert mouse adiponectin-UCP1 into the porcine endogenous UCP1 locus. The resultant UCP1 knock-in (KI) pigs showed an improved ability to maintain body temperature during acute cold exposure, but they did not have alterations in physical activity levels or total daily energy expenditure (DEE). Furthermore, ectopic UCP1 expression in white adipose tissue (WAT) dramatically decreased fat deposition by 4.89% (P < 0.01), consequently increasing carcass lean percentage (CLP; P < 0.05). Mechanism studies indicated that the loss of fat upon UCP1 activation in WAT was linked to elevated lipolysis. UCP1 KI pigs are a potentially valuable resource for agricultural production through their combination of cold adaptation, which improves pig welfare and reduces economic losses, with reduced fat deposition and increased lean meat production.

[Production of GHR double-allelic knockout Bama pig by TALENs and handmade cloning].

DNA editing techniques for targeted genome modification have witnessed remarkable advances and been widely used in various organisms. However, traditional gene targeting and cloning method has been shown to be low efficient, time-consuming and expensive for generating knockout animals, especially for big animals. Here we report the generation of site-specific genome modified pig with the newly developed artificially engineered sequence-specific endonucleases (transcription activator-like effector nuclease, TALENs) and handmade cloning (HMC) methods. First, we constructed the porcine GHR-knockout vector according to TALENs kit protocol. To obtain the nuclear donor, the fetal fibroblast cell of Bama (BM) pig were transfected with GHR-knockout vector in G418 selection medium. We collected 173 cell for further positive identification which showed that 46.2% (78/173) of the clones were GHR-knockout cell strains. We chose one bi-allelic knockout cell strain as nuclear donor to produce reconstructed embryos by HMC. It was shown that the blastocyst rate was 43.5% at the 6(th) day in vitro, then 654 HMC-blastocysts were transplanted to uterus of six recipient sows. Finally, a total of 10 live offspring were delivered including 7 bi-allelic knockout piglets. Fibroblasts were obtained from ear biopsies for GHR knockout detection. The body weight of the piglets was measured consecutively, and it was found that the GHR(-)(/)(-) pigs were only 50% smaller than that of the controls at the 20(th) week. In conclusion, our results indicate that TALENs and HMC technology can rapidly and efficiently produce knockout animals for agricultural and biomedical research.

Observation of ion-cyclotron-frequency mode conversion plasma rotation on HT-7

In this paper, we present a study on D?H (7Li) plasmas with moderate hydrogen concentration (?15%) on the HT-7 tokamak. Enhanced density fluctuation induced by ion cyclotron range of frequencies (ICRF) at the centre of the plasma is observed by a continuous wave CO2 (??=?10.6??m) collective scattering system. At the same time, the Doppler shift VD due to plasma rotation in the mode-converted ICRF D?H (7Li) plasmas is observed experimentally for the first time on the HT-7 tokamak, and the Doppler shift VD is approximately linear versus the change in plasma stored energy ?W.

Recycling behaviour during long pulse discharges after ICRF boronization in the HT-7 tokamak

The evolution of recycling behaviour has been investigated during long pulse discharges in the HT-7 tokamak after ICRF boronization (C2B10H12) using the H/(H+D) ratio and the edge recycling coefficient R. After boronization, impurity reduction is observed, attributed to the fresh boron film, but the recycling coefficient can exceed unity due to a large amount of hydrogen absorbed in the film, leading to an uncontrollable density rise and discharge termination. When the H/(H+D) ratio was reduced to less than 25%, the electron density was easily controlled. The longest discharge, up to 240 s with central electron temperature Te(0) of about 1.0 keV and central electron density ne(0) of 0.8 × 1019 m−3, was achieved following boronization. After many discharges the effectiveness of boron film was weakened, and the density rise was correlated with an increase in both carbon and oxygen radiation which limited the duration of long pulse discharges.

No seasonal variation in physical activity of Han Chinese living in Beijing

BackgroundPhysical activity (PA) is widely acknowledged to be beneficial to health and wellbeing, and is potentially influenced by a variety of environmental factors such as ambient temperature, weather conditions and air pollution levels. Since these factors vary seasonally, physical activity participation may also respond seasonally. Current population studies to profile physical activity often sample individuals only once, and this may result in biased estimates if there is strong seasonal variation.MethodsWe conducted a study of 40 Han Chinese adults living in Beijing using GT3X accelerometers. We measured PA levels every two months across a complete year, while simultaneously monitoring ambient temperatures and air pollution levels. Average hourly vector magnitude (VM) and percentage time spent at each PA intensity (sedentary to light, moderate, vigorous and very vigorous) were measured. General Linear models (GLMs) were used to explore the effects of time of day, temperature and PM 2.5 levels on PA. One way ANOVA was used to test whether there were seasonal differences in body weight and body fatness.ResultsThe main factors influencing activity levels were the time of day and individual characteristics including age and body fatness, but there was no significant difference between the months. In addition, there was no significant impact of either ambient temperature or air pollution levels (PM2.5). There were also no significant differences over the year in the time spent at sedentary-light, moderate and very vigorous PA levels, but for vigorous PA level which occupied less than 0.5% daily physical activity, both month and individual were significant factors.ConclusionsThe relatively constant pattern of urban daily life, independent of time of year, may override the potential impacts of environmental factors that would be anticipated to impact PA levels. These subjects did not specifically avoid activity coincident with elevated air pollution levels (PM2.5). Single week long measurements of physical activity could provide a representative measurement of the physical active levels in this population.

Performance predictions of RF heated plasma in EAST

Scenario development of high power L- and H-mode plasmas in the Experimental Advanced Superconducting Tokamak (EAST) tokamak is reported. The simulations use PTRANSP in combination with TSC to explore EAST plasmas with various radio frequency (RF) auxiliary heating methods, including ion cyclotron resonant heating (ICRH) and lower hybrid current drive. The GLF23 transport model is found to give a better fit to temperature measurements compared with the MMM95 and MMM08 models. A series of ICRH simulations are performed to optimize parameters of a new ICRH system in EAST. The highest plasma stored energy and other related plasma parameters using the current auxiliary power limits are predicted. The discharge length of high power plasma can be 8–200 s, depending on the volt–second consumption in different scenarios. Various phenomena are reported including the influence of different fractions of RF power on their deposition behavior, and on thermal diffusivity, the linear relation between q0 and LHW power fraction, different behavior of fast ions between L- and H-mode plasmas. The scenario development is predicted to improve the performance of EAST.

Fast generation of an inward electric field due to ion orbit losses in the tokamak edge plasma during transition from low-to-high confinement

The formation of radial electric field Er in the tokamak edge region is calculated based on the collisionless ion orbit loss. The ion orbit loss generates a negative Er, which in turn affects the ion loss. As a result, Er can saturate at either a low or a high value, depending on the plasma parameters. When the ion temperature in the plasma edge is higher than a threshold, a self-sustaining growth in both ion loss and Er is found, leading to a high saturation value of Er in milliseconds. This mechanism provides a possible explanation for the formation of a strong radial electric field during the transition from the low (L) to the high (H) confinement regime observed in tokamak edge plasmas.

The longer life and high performance of lithium containing coatings developed by ICRF in the HT-7 superconducting tokamak☆

Abstract A new wall conditioning method, lithium containing silicon coatings (α-C:H/Li–Si) in situ realized by means of ion cyclotron range of frequency plasma assisted chemical vapor deposition, has been successfully developed in the HT-7 superconducting tokamak, which leads to not only the effective suppression of carbon and oxygen impurities, but also lower hydrogen recycling than siliconization. After the wall conditioning, the impurity level in the vacuum vessel of HT-7 device measured by QMS and spectroscopy was largely reduced and obviously lower than siliconization and even approaches lithium in situ coatings. The depth profile of deposition was investigated by Auger surface analysis. The decreases of edge plasma temperature and electron density showed that the plasma confinement has been significantly improved comparing with siliconization, and is sustained for nearly 350 shots.

Screening and SNP mapping of copper-resistant mutations in C. elegans.

Copper plays critical roles in biological system; however, it is toxic in excess. To identify novel genes involved in copper metabolism, we performed a whole genome-wide genetic screen in C. elegans model organism to search for mutants which are resistant to excessive copper. Wild type (N2) L4 worms were mutagenized with ethylmethane sulfonate (EMS), and the F₂progeny were screened on culture medium with excess copper. Two copper-resistant mutants, ms₁and ms₂, were recovered from the screening of 100 000 hyploid genomes. No obvious developmental defects were observed in ms₁and ms₂mutants, and they were able to grow into adults on screen medium plate, but N₂worms arrested in L₁stage. Results of backcross test suggested that copper-resistant phenotype in ms₁may be controlled by a single recessive gene, but probably there are mutations in multiple genes in ms₂, as no copper resistant worms could be found in F₂progeny when ms₂mutants were backcrossed with N₂worms. To determine the mutation positions of ms₁, we employed single nucleotide polymorphisms (SNPs) mapping. Our mapping results indicated that ms₁mutation is on chromosome II (LGII). By analysis of 8 SNP markers from -18 to 23 on LGII, we found that ms₁mutation is at approximately LGII:-6. Further study on ms₁mutants will provide insights into copper metabolism and its regulation.